/* * dlls/rsaenh/mpi.c * Multi Precision Integer functions * * Copyright 2004 Michael Jung * Based on public domain code by Tom St Denis (tomstdenis@iahu.ca) * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA */ /* * This file contains code from the LibTomCrypt cryptographic * library written by Tom St Denis (tomstdenis@iahu.ca). LibTomCrypt * is in the public domain. The code in this file is tailored to * special requirements. Take a look at http://libtomcrypt.org for the * original version. */ #include <stdarg.h> #include "tomcrypt.h" /* computes the modular inverse via binary extended euclidean algorithm, * that is c = 1/a mod b * * Based on slow invmod except this is optimized for the case where b is * odd as per HAC Note 14.64 on pp. 610 */ int fast_mp_invmod (mp_int * a, mp_int * b, mp_int * c) { mp_int x, y, u, v, B, D; int res, neg; /* 2. [modified] b must be odd */ if (mp_iseven (b) == 1) { return MP_VAL; } /* init all our temps */ if ((res = mp_init_multi(&x, &y, &u, &v, &B, &D, NULL)) != MP_OKAY) { return res; } /* x == modulus, y == value to invert */ if ((res = mp_copy (b, &x)) != MP_OKAY) { goto __ERR; } /* we need y = |a| */ if ((res = mp_abs (a, &y)) != MP_OKAY) { goto __ERR; } /* 3. u=x, v=y, A=1, B=0, C=0,D=1 */ if ((res = mp_copy (&x, &u)) != MP_OKAY) { goto __ERR; } if ((res = mp_copy (&y, &v)) != MP_OKAY) { goto __ERR; } mp_set (&D, 1); top: /* 4. while u is even do */ while (mp_iseven (&u) == 1) { /* 4.1 u = u/2 */ if ((res = mp_div_2 (&u, &u)) != MP_OKAY) { goto __ERR; } /* 4.2 if B is odd then */ if (mp_isodd (&B) == 1) { if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) { goto __ERR; } } /* B = B/2 */ if ((res = mp_div_2 (&B, &B)) != MP_OKAY) { goto __ERR; } } /* 5. while v is even do */ while (mp_iseven (&v) == 1) { /* 5.1 v = v/2 */ if ((res = mp_div_2 (&v, &v)) != MP_OKAY) { goto __ERR; } /* 5.2 if D is odd then */ if (mp_isodd (&D) == 1) { /* D = (D-x)/2 */ if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) { goto __ERR; } } /* D = D/2 */ if ((res = mp_div_2 (&D, &D)) != MP_OKAY) { goto __ERR; } } /* 6. if u >= v then */ if (mp_cmp (&u, &v) != MP_LT) { /* u = u - v, B = B - D */ if ((res = mp_sub (&u, &v, &u)) != MP_OKAY) { goto __ERR; } if ((res = mp_sub (&B, &D, &B)) != MP_OKAY) { goto __ERR; } } else { /* v - v - u, D = D - B */ if ((res = mp_sub (&v, &u, &v)) != MP_OKAY) { goto __ERR; } if ((res = mp_sub (&D, &B, &D)) != MP_OKAY) { goto __ERR; } } /* if not zero goto step 4 */ if (mp_iszero (&u) == 0) { goto top; } /* now a = C, b = D, gcd == g*v */ /* if v != 1 then there is no inverse */ if (mp_cmp_d (&v, 1) != MP_EQ) { res = MP_VAL; goto __ERR; } /* b is now the inverse */ neg = a->sign; while (D.sign == MP_NEG) { if ((res = mp_add (&D, b, &D)) != MP_OKAY) { goto __ERR; } } mp_exch (&D, c); c->sign = neg; res = MP_OKAY; __ERR:mp_clear_multi (&x, &y, &u, &v, &B, &D, NULL); return res; } /* computes xR**-1 == x (mod N) via Montgomery Reduction * * This is an optimized implementation of montgomery_reduce * which uses the comba method to quickly calculate the columns of the * reduction. * * Based on Algorithm 14.32 on pp.601 of HAC. */ int fast_mp_montgomery_reduce (mp_int * x, mp_int * n, mp_digit rho) { int ix, res, olduse; mp_word W[MP_WARRAY]; /* get old used count */ olduse = x->used; /* grow a as required */ if (x->alloc < n->used + 1) { if ((res = mp_grow (x, n->used + 1)) != MP_OKAY) { return res; } } /* first we have to get the digits of the input into * an array of double precision words W[...] */ { register mp_word *_W; register mp_digit *tmpx; /* alias for the W[] array */ _W = W; /* alias for the digits of x*/ tmpx = x->dp; /* copy the digits of a into W[0..a->used-1] */ for (ix = 0; ix < x->used; ix++) { *_W++ = *tmpx++; } /* zero the high words of W[a->used..m->used*2] */ for (; ix < n->used * 2 + 1; ix++) { *_W++ = 0; } } /* now we proceed to zero successive digits * from the least significant upwards */ for (ix = 0; ix < n->used; ix++) { /* mu = ai * m' mod b * * We avoid a double precision multiplication (which isn't required) * by casting the value down to a mp_digit. Note this requires * that W[ix-1] have the carry cleared (see after the inner loop) */ register mp_digit mu; mu = (mp_digit) (((W[ix] & MP_MASK) * rho) & MP_MASK); /* a = a + mu * m * b**i * * This is computed in place and on the fly. The multiplication * by b**i is handled by offseting which columns the results * are added to. * * Note the comba method normally doesn't handle carries in the * inner loop In this case we fix the carry from the previous * column since the Montgomery reduction requires digits of the * result (so far) [see above] to work. This is * handled by fixing up one carry after the inner loop. The * carry fixups are done in order so after these loops the * first m->used words of W[] have the carries fixed */ { register int iy; register mp_digit *tmpn; register mp_word *_W; /* alias for the digits of the modulus */ tmpn = n->dp; /* Alias for the columns set by an offset of ix */ _W = W + ix; /* inner loop */ for (iy = 0; iy < n->used; iy++) { *_W++ += ((mp_word)mu) * ((mp_word)*tmpn++); } } /* now fix carry for next digit, W[ix+1] */ W[ix + 1] += W[ix] >> ((mp_word) DIGIT_BIT); } /* now we have to propagate the carries and * shift the words downward [all those least * significant digits we zeroed]. */ { register mp_digit *tmpx; register mp_word *_W, *_W1; /* nox fix rest of carries */ /* alias for current word */ _W1 = W + ix; /* alias for next word, where the carry goes */ _W = W + ++ix; for (; ix <= n->used * 2 + 1; ix++) { *_W++ += *_W1++ >> ((mp_word) DIGIT_BIT); } /* copy out, A = A/b**n * * The result is A/b**n but instead of converting from an * array of mp_word to mp_digit than calling mp_rshd * we just copy them in the right order */ /* alias for destination word */ tmpx = x->dp; /* alias for shifted double precision result */ _W = W + n->used; for (ix = 0; ix < n->used + 1; ix++) { *tmpx++ = (mp_digit)(*_W++ & ((mp_word) MP_MASK)); } /* zero oldused digits, if the input a was larger than * m->used+1 we'll have to clear the digits */ for (; ix < olduse; ix++) { *tmpx++ = 0; } } /* set the max used and clamp */ x->used = n->used + 1; mp_clamp (x); /* if A >= m then A = A - m */ if (mp_cmp_mag (x, n) != MP_LT) { return s_mp_sub (x, n, x); } return MP_OKAY; } /* Fast (comba) multiplier * * This is the fast column-array [comba] multiplier. It is * designed to compute the columns of the product first * then handle the carries afterwards. This has the effect * of making the nested loops that compute the columns very * simple and schedulable on super-scalar processors. * * This has been modified to produce a variable number of * digits of output so if say only a half-product is required * you don't have to compute the upper half (a feature * required for fast Barrett reduction). * * Based on Algorithm 14.12 on pp.595 of HAC. * */ int fast_s_mp_mul_digs (mp_int * a, mp_int * b, mp_int * c, int digs) { int olduse, res, pa, ix, iz; mp_digit W[MP_WARRAY]; register mp_word _W; /* grow the destination as required */ if (c->alloc < digs) { if ((res = mp_grow (c, digs)) != MP_OKAY) { return res; } } /* number of output digits to produce */ pa = MIN(digs, a->used + b->used); /* clear the carry */ _W = 0; for (ix = 0; ix <= pa; ix++) { int tx, ty; int iy; mp_digit *tmpx, *tmpy; /* get offsets into the two bignums */ ty = MIN(b->used-1, ix); tx = ix - ty; /* setup temp aliases */ tmpx = a->dp + tx; tmpy = b->dp + ty; /* this is the number of times the loop will iterrate, essentially its while (tx++ < a->used && ty-- >= 0) { ... } */ iy = MIN(a->used-tx, ty+1); /* execute loop */ for (iz = 0; iz < iy; ++iz) { _W += ((mp_word)*tmpx++)*((mp_word)*tmpy--); } /* store term */ W[ix] = ((mp_digit)_W) & MP_MASK; /* make next carry */ _W = _W >> ((mp_word)DIGIT_BIT); } /* setup dest */ olduse = c->used; c->used = digs; { register mp_digit *tmpc; tmpc = c->dp; for (ix = 0; ix < digs; ix++) { /* now extract the previous digit [below the carry] */ *tmpc++ = W[ix]; } /* clear unused digits [that existed in the old copy of c] */ for (; ix < olduse; ix++) { *tmpc++ = 0; } } mp_clamp (c); return MP_OKAY; } /* this is a modified version of fast_s_mul_digs that only produces * output digits *above* digs. See the comments for fast_s_mul_digs * to see how it works. * * This is used in the Barrett reduction since for one of the multiplications * only the higher digits were needed. This essentially halves the work. * * Based on Algorithm 14.12 on pp.595 of HAC. */ int fast_s_mp_mul_high_digs (mp_int * a, mp_int * b, mp_int * c, int digs) { int olduse, res, pa, ix, iz; mp_digit W[MP_WARRAY]; mp_word _W; /* grow the destination as required */ pa = a->used + b->used; if (c->alloc < pa) { if ((res = mp_grow (c, pa)) != MP_OKAY) { return res; } } /* number of output digits to produce */ pa = a->used + b->used; _W = 0; for (ix = digs; ix <= pa; ix++) { int tx, ty, iy; mp_digit *tmpx, *tmpy; /* get offsets into the two bignums */ ty = MIN(b->used-1, ix); tx = ix - ty; /* setup temp aliases */ tmpx = a->dp + tx; tmpy = b->dp + ty; /* this is the number of times the loop will iterrate, essentially its while (tx++ < a->used && ty-- >= 0) { ... } */ iy = MIN(a->used-tx, ty+1); /* execute loop */ for (iz = 0; iz < iy; iz++) { _W += ((mp_word)*tmpx++)*((mp_word)*tmpy--); } /* store term */ W[ix] = ((mp_digit)_W) & MP_MASK; /* make next carry */ _W = _W >> ((mp_word)DIGIT_BIT); } /* setup dest */ olduse = c->used; c->used = pa; { register mp_digit *tmpc; tmpc = c->dp + digs; for (ix = digs; ix <= pa; ix++) { /* now extract the previous digit [below the carry] */ *tmpc++ = W[ix]; } /* clear unused digits [that existed in the old copy of c] */ for (; ix < olduse; ix++) { *tmpc++ = 0; } } mp_clamp (c); return MP_OKAY; } /* fast squaring * * This is the comba method where the columns of the product * are computed first then the carries are computed. This * has the effect of making a very simple inner loop that * is executed the most * * W2 represents the outer products and W the inner. * * A further optimizations is made because the inner * products are of the form "A * B * 2". The *2 part does * not need to be computed until the end which is good * because 64-bit shifts are slow! * * Based on Algorithm 14.16 on pp.597 of HAC. * */ /* the jist of squaring... you do like mult except the offset of the tmpx [one that starts closer to zero] can't equal the offset of tmpy. So basically you set up iy like before then you min it with (ty-tx) so that it never happens. You double all those you add in the inner loop After that loop you do the squares and add them in. Remove W2 and don't memset W */ int fast_s_mp_sqr (mp_int * a, mp_int * b) { int olduse, res, pa, ix, iz; mp_digit W[MP_WARRAY], *tmpx; mp_word W1; /* grow the destination as required */ pa = a->used + a->used; if (b->alloc < pa) { if ((res = mp_grow (b, pa)) != MP_OKAY) { return res; } } /* number of output digits to produce */ W1 = 0; for (ix = 0; ix <= pa; ix++) { int tx, ty, iy; mp_word _W; mp_digit *tmpy; /* clear counter */ _W = 0; /* get offsets into the two bignums */ ty = MIN(a->used-1, ix); tx = ix - ty; /* setup temp aliases */ tmpx = a->dp + tx; tmpy = a->dp + ty; /* this is the number of times the loop will iterrate, essentially its while (tx++ < a->used && ty-- >= 0) { ... } */ iy = MIN(a->used-tx, ty+1); /* now for squaring tx can never equal ty * we halve the distance since they approach at a rate of 2x * and we have to round because odd cases need to be executed */ iy = MIN(iy, (ty-tx+1)>>1); /* execute loop */ for (iz = 0; iz < iy; iz++) { _W += ((mp_word)*tmpx++)*((mp_word)*tmpy--); } /* double the inner product and add carry */ _W = _W + _W + W1; /* even columns have the square term in them */ if ((ix&1) == 0) { _W += ((mp_word)a->dp[ix>>1])*((mp_word)a->dp[ix>>1]); } /* store it */ W[ix] = _W; /* make next carry */ W1 = _W >> ((mp_word)DIGIT_BIT); } /* setup dest */ olduse = b->used; b->used = a->used+a->used; { mp_digit *tmpb; tmpb = b->dp; for (ix = 0; ix < pa; ix++) { *tmpb++ = W[ix] & MP_MASK; } /* clear unused digits [that existed in the old copy of c] */ for (; ix < olduse; ix++) { *tmpb++ = 0; } } mp_clamp (b); return MP_OKAY; } /* computes a = 2**b * * Simple algorithm which zeroes the int, grows it then just sets one bit * as required. */ int mp_2expt (mp_int * a, int b) { int res; /* zero a as per default */ mp_zero (a); /* grow a to accommodate the single bit */ if ((res = mp_grow (a, b / DIGIT_BIT + 1)) != MP_OKAY) { return res; } /* set the used count of where the bit will go */ a->used = b / DIGIT_BIT + 1; /* put the single bit in its place */ a->dp[b / DIGIT_BIT] = ((mp_digit)1) << (b % DIGIT_BIT); return MP_OKAY; } /* b = |a| * * Simple function copies the input and fixes the sign to positive */ int mp_abs (mp_int * a, mp_int * b) { int res; /* copy a to b */ if (a != b) { if ((res = mp_copy (a, b)) != MP_OKAY) { return res; } } /* force the sign of b to positive */ b->sign = MP_ZPOS; return MP_OKAY; } /* high level addition (handles signs) */ int mp_add (mp_int * a, mp_int * b, mp_int * c) { int sa, sb, res; /* get sign of both inputs */ sa = a->sign; sb = b->sign; /* handle two cases, not four */ if (sa == sb) { /* both positive or both negative */ /* add their magnitudes, copy the sign */ c->sign = sa; res = s_mp_add (a, b, c); } else { /* one positive, the other negative */ /* subtract the one with the greater magnitude from */ /* the one of the lesser magnitude. The result gets */ /* the sign of the one with the greater magnitude. */ if (mp_cmp_mag (a, b) == MP_LT) { c->sign = sb; res = s_mp_sub (b, a, c); } else { c->sign = sa; res = s_mp_sub (a, b, c); } } return res; } /* single digit addition */ int mp_add_d (mp_int * a, mp_digit b, mp_int * c) { int res, ix, oldused; mp_digit *tmpa, *tmpc, mu; /* grow c as required */ if (c->alloc < a->used + 1) { if ((res = mp_grow(c, a->used + 1)) != MP_OKAY) { return res; } } /* if a is negative and |a| >= b, call c = |a| - b */ if (a->sign == MP_NEG && (a->used > 1 || a->dp[0] >= b)) { /* temporarily fix sign of a */ a->sign = MP_ZPOS; /* c = |a| - b */ res = mp_sub_d(a, b, c); /* fix sign */ a->sign = c->sign = MP_NEG; return res; } /* old number of used digits in c */ oldused = c->used; /* sign always positive */ c->sign = MP_ZPOS; /* source alias */ tmpa = a->dp; /* destination alias */ tmpc = c->dp; /* if a is positive */ if (a->sign == MP_ZPOS) { /* add digit, after this we're propagating * the carry. */ *tmpc = *tmpa++ + b; mu = *tmpc >> DIGIT_BIT; *tmpc++ &= MP_MASK; /* now handle rest of the digits */ for (ix = 1; ix < a->used; ix++) { *tmpc = *tmpa++ + mu; mu = *tmpc >> DIGIT_BIT; *tmpc++ &= MP_MASK; } /* set final carry */ ix++; *tmpc++ = mu; /* setup size */ c->used = a->used + 1; } else { /* a was negative and |a| < b */ c->used = 1; /* the result is a single digit */ if (a->used == 1) { *tmpc++ = b - a->dp[0]; } else { *tmpc++ = b; } /* setup count so the clearing of oldused * can fall through correctly */ ix = 1; } /* now zero to oldused */ while (ix++ < oldused) { *tmpc++ = 0; } mp_clamp(c); return MP_OKAY; } /* trim unused digits * * This is used to ensure that leading zero digits are * trimed and the leading "used" digit will be non-zero * Typically very fast. Also fixes the sign if there * are no more leading digits */ void mp_clamp (mp_int * a) { /* decrease used while the most significant digit is * zero. */ while (a->used > 0 && a->dp[a->used - 1] == 0) { --(a->used); } /* reset the sign flag if used == 0 */ if (a->used == 0) { a->sign = MP_ZPOS; } } /* clear one (frees) */ void mp_clear (mp_int * a) { int i; /* only do anything if a hasn't been freed previously */ if (a->dp != NULL) { /* first zero the digits */ for (i = 0; i < a->used; i++) { a->dp[i] = 0; } /* free ram */ free(a->dp); /* reset members to make debugging easier */ a->dp = NULL; a->alloc = a->used = 0; a->sign = MP_ZPOS; } } void mp_clear_multi(mp_int *mp, ...) { mp_int* next_mp = mp; va_list args; va_start(args, mp); while (next_mp != NULL) { mp_clear(next_mp); next_mp = va_arg(args, mp_int*); } va_end(args); } /* compare two ints (signed)*/ int mp_cmp (mp_int * a, mp_int * b) { /* compare based on sign */ if (a->sign != b->sign) { if (a->sign == MP_NEG) { return MP_LT; } else { return MP_GT; } } /* compare digits */ if (a->sign == MP_NEG) { /* if negative compare opposite direction */ return mp_cmp_mag(b, a); } else { return mp_cmp_mag(a, b); } } /* compare a digit */ int mp_cmp_d(mp_int * a, mp_digit b) { /* compare based on sign */ if (a->sign == MP_NEG) { return MP_LT; } /* compare based on magnitude */ if (a->used > 1) { return MP_GT; } /* compare the only digit of a to b */ if (a->dp[0] > b) { return MP_GT; } else if (a->dp[0] < b) { return MP_LT; } else { return MP_EQ; } } /* compare maginitude of two ints (unsigned) */ int mp_cmp_mag (mp_int * a, mp_int * b) { int n; mp_digit *tmpa, *tmpb; /* compare based on # of non-zero digits */ if (a->used > b->used) { return MP_GT; } if (a->used < b->used) { return MP_LT; } /* alias for a */ tmpa = a->dp + (a->used - 1); /* alias for b */ tmpb = b->dp + (a->used - 1); /* compare based on digits */ for (n = 0; n < a->used; ++n, --tmpa, --tmpb) { if (*tmpa > *tmpb) { return MP_GT; } if (*tmpa < *tmpb) { return MP_LT; } } return MP_EQ; } static const int lnz[16] = { 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0 }; /* Counts the number of lsbs which are zero before the first zero bit */ int mp_cnt_lsb(mp_int *a) { int x; mp_digit q, qq; /* easy out */ if (mp_iszero(a) == 1) { return 0; } /* scan lower digits until non-zero */ for (x = 0; x < a->used && a->dp[x] == 0; x++); q = a->dp[x]; x *= DIGIT_BIT; /* now scan this digit until a 1 is found */ if ((q & 1) == 0) { do { qq = q & 15; x += lnz[qq]; q >>= 4; } while (qq == 0); } return x; } /* copy, b = a */ int mp_copy (const mp_int * a, mp_int * b) { int res, n; /* if dst == src do nothing */ if (a == b) { return MP_OKAY; } /* grow dest */ if (b->alloc < a->used) { if ((res = mp_grow (b, a->used)) != MP_OKAY) { return res; } } /* zero b and copy the parameters over */ { register mp_digit *tmpa, *tmpb; /* pointer aliases */ /* source */ tmpa = a->dp; /* destination */ tmpb = b->dp; /* copy all the digits */ for (n = 0; n < a->used; n++) { *tmpb++ = *tmpa++; } /* clear high digits */ for (; n < b->used; n++) { *tmpb++ = 0; } } /* copy used count and sign */ b->used = a->used; b->sign = a->sign; return MP_OKAY; } /* returns the number of bits in an int */ int mp_count_bits (mp_int * a) { int r; mp_digit q; /* shortcut */ if (a->used == 0) { return 0; } /* get number of digits and add that */ r = (a->used - 1) * DIGIT_BIT; /* take the last digit and count the bits in it */ q = a->dp[a->used - 1]; while (q > ((mp_digit) 0)) { ++r; q >>= ((mp_digit) 1); } return r; } /* integer signed division. * c*b + d == a [e.g. a/b, c=quotient, d=remainder] * HAC pp.598 Algorithm 14.20 * * Note that the description in HAC is horribly * incomplete. For example, it doesn't consider * the case where digits are removed from 'x' in * the inner loop. It also doesn't consider the * case that y has fewer than three digits, etc.. * * The overall algorithm is as described as * 14.20 from HAC but fixed to treat these cases. */ int mp_div (mp_int * a, mp_int * b, mp_int * c, mp_int * d) { mp_int q, x, y, t1, t2; int res, n, t, i, norm, neg; /* is divisor zero ? */ if (mp_iszero (b) == 1) { return MP_VAL; } /* if a < b then q=0, r = a */ if (mp_cmp_mag (a, b) == MP_LT) { if (d != NULL) { res = mp_copy (a, d); } else { res = MP_OKAY; } if (c != NULL) { mp_zero (c); } return res; } if ((res = mp_init_size (&q, a->used + 2)) != MP_OKAY) { return res; } q.used = a->used + 2; if ((res = mp_init (&t1)) != MP_OKAY) { goto __Q; } if ((res = mp_init (&t2)) != MP_OKAY) { goto __T1; } if ((res = mp_init_copy (&x, a)) != MP_OKAY) { goto __T2; } if ((res = mp_init_copy (&y, b)) != MP_OKAY) { goto __X; } /* fix the sign */ neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG; x.sign = y.sign = MP_ZPOS; /* normalize both x and y, ensure that y >= b/2, [b == 2**DIGIT_BIT] */ norm = mp_count_bits(&y) % DIGIT_BIT; if (norm < (int)(DIGIT_BIT-1)) { norm = (DIGIT_BIT-1) - norm; if ((res = mp_mul_2d (&x, norm, &x)) != MP_OKAY) { goto __Y; } if ((res = mp_mul_2d (&y, norm, &y)) != MP_OKAY) { goto __Y; } } else { norm = 0; } /* note hac does 0 based, so if used==5 then its 0,1,2,3,4, e.g. use 4 */ n = x.used - 1; t = y.used - 1; /* while (x >= y*b**n-t) do { q[n-t] += 1; x -= y*b**{n-t} } */ if ((res = mp_lshd (&y, n - t)) != MP_OKAY) { /* y = y*b**{n-t} */ goto __Y; } while (mp_cmp (&x, &y) != MP_LT) { ++(q.dp[n - t]); if ((res = mp_sub (&x, &y, &x)) != MP_OKAY) { goto __Y; } } /* reset y by shifting it back down */ mp_rshd (&y, n - t); /* step 3. for i from n down to (t + 1) */ for (i = n; i >= (t + 1); i--) { if (i > x.used) { continue; } /* step 3.1 if xi == yt then set q{i-t-1} to b-1, * otherwise set q{i-t-1} to (xi*b + x{i-1})/yt */ if (x.dp[i] == y.dp[t]) { q.dp[i - t - 1] = ((((mp_digit)1) << DIGIT_BIT) - 1); } else { mp_word tmp; tmp = ((mp_word) x.dp[i]) << ((mp_word) DIGIT_BIT); tmp |= ((mp_word) x.dp[i - 1]); tmp /= ((mp_word) y.dp[t]); if (tmp > (mp_word) MP_MASK) tmp = MP_MASK; q.dp[i - t - 1] = (mp_digit) (tmp & (mp_word) (MP_MASK)); } /* while (q{i-t-1} * (yt * b + y{t-1})) > xi * b**2 + xi-1 * b + xi-2 do q{i-t-1} -= 1; */ q.dp[i - t - 1] = (q.dp[i - t - 1] + 1) & MP_MASK; do { q.dp[i - t - 1] = (q.dp[i - t - 1] - 1) & MP_MASK; /* find left hand */ mp_zero (&t1); t1.dp[0] = (t - 1 < 0) ? 0 : y.dp[t - 1]; t1.dp[1] = y.dp[t]; t1.used = 2; if ((res = mp_mul_d (&t1, q.dp[i - t - 1], &t1)) != MP_OKAY) { goto __Y; } /* find right hand */ t2.dp[0] = (i - 2 < 0) ? 0 : x.dp[i - 2]; t2.dp[1] = (i - 1 < 0) ? 0 : x.dp[i - 1]; t2.dp[2] = x.dp[i]; t2.used = 3; } while (mp_cmp_mag(&t1, &t2) == MP_GT); /* step 3.3 x = x - q{i-t-1} * y * b**{i-t-1} */ if ((res = mp_mul_d (&y, q.dp[i - t - 1], &t1)) != MP_OKAY) { goto __Y; } if ((res = mp_lshd (&t1, i - t - 1)) != MP_OKAY) { goto __Y; } if ((res = mp_sub (&x, &t1, &x)) != MP_OKAY) { goto __Y; } /* if x < 0 then { x = x + y*b**{i-t-1}; q{i-t-1} -= 1; } */ if (x.sign == MP_NEG) { if ((res = mp_copy (&y, &t1)) != MP_OKAY) { goto __Y; } if ((res = mp_lshd (&t1, i - t - 1)) != MP_OKAY) { goto __Y; } if ((res = mp_add (&x, &t1, &x)) != MP_OKAY) { goto __Y; } q.dp[i - t - 1] = (q.dp[i - t - 1] - 1UL) & MP_MASK; } } /* now q is the quotient and x is the remainder * [which we have to normalize] */ /* get sign before writing to c */ x.sign = x.used == 0 ? MP_ZPOS : a->sign; if (c != NULL) { mp_clamp (&q); mp_exch (&q, c); c->sign = neg; } if (d != NULL) { mp_div_2d (&x, norm, &x, NULL); mp_exch (&x, d); } res = MP_OKAY; __Y:mp_clear (&y); __X:mp_clear (&x); __T2:mp_clear (&t2); __T1:mp_clear (&t1); __Q:mp_clear (&q); return res; } /* b = a/2 */ int mp_div_2(mp_int * a, mp_int * b) { int x, res, oldused; /* copy */ if (b->alloc < a->used) { if ((res = mp_grow (b, a->used)) != MP_OKAY) { return res; } } oldused = b->used; b->used = a->used; { register mp_digit r, rr, *tmpa, *tmpb; /* source alias */ tmpa = a->dp + b->used - 1; /* dest alias */ tmpb = b->dp + b->used - 1; /* carry */ r = 0; for (x = b->used - 1; x >= 0; x--) { /* get the carry for the next iteration */ rr = *tmpa & 1; /* shift the current digit, add in carry and store */ *tmpb-- = (*tmpa-- >> 1) | (r << (DIGIT_BIT - 1)); /* forward carry to next iteration */ r = rr; } /* zero excess digits */ tmpb = b->dp + b->used; for (x = b->used; x < oldused; x++) { *tmpb++ = 0; } } b->sign = a->sign; mp_clamp (b); return MP_OKAY; } /* shift right by a certain bit count (store quotient in c, optional remainder in d) */ int mp_div_2d (mp_int * a, int b, mp_int * c, mp_int * d) { mp_digit D, r, rr; int x, res; mp_int t; /* if the shift count is <= 0 then we do no work */ if (b <= 0) { res = mp_copy (a, c); if (d != NULL) { mp_zero (d); } return res; } if ((res = mp_init (&t)) != MP_OKAY) { return res; } /* get the remainder */ if (d != NULL) { if ((res = mp_mod_2d (a, b, &t)) != MP_OKAY) { mp_clear (&t); return res; } } /* copy */ if ((res = mp_copy (a, c)) != MP_OKAY) { mp_clear (&t); return res; } /* shift by as many digits in the bit count */ if (b >= (int)DIGIT_BIT) { mp_rshd (c, b / DIGIT_BIT); } /* shift any bit count < DIGIT_BIT */ D = (mp_digit) (b % DIGIT_BIT); if (D != 0) { register mp_digit *tmpc, mask, shift; /* mask */ mask = (((mp_digit)1) << D) - 1; /* shift for lsb */ shift = DIGIT_BIT - D; /* alias */ tmpc = c->dp + (c->used - 1); /* carry */ r = 0; for (x = c->used - 1; x >= 0; x--) { /* get the lower bits of this word in a temp */ rr = *tmpc & mask; /* shift the current word and mix in the carry bits from the previous word */ *tmpc = (*tmpc >> D) | (r << shift); --tmpc; /* set the carry to the carry bits of the current word found above */ r = rr; } } mp_clamp (c); if (d != NULL) { mp_exch (&t, d); } mp_clear (&t); return MP_OKAY; } static int s_is_power_of_two(mp_digit b, int *p) { int x; for (x = 1; x < DIGIT_BIT; x++) { if (b == (((mp_digit)1)<<x)) { *p = x; return 1; } } return 0; } /* single digit division (based on routine from MPI) */ int mp_div_d (mp_int * a, mp_digit b, mp_int * c, mp_digit * d) { mp_int q; mp_word w; mp_digit t; int res, ix; /* cannot divide by zero */ if (b == 0) { return MP_VAL; } /* quick outs */ if (b == 1 || mp_iszero(a) == 1) { if (d != NULL) { *d = 0; } if (c != NULL) { return mp_copy(a, c); } return MP_OKAY; } /* power of two ? */ if (s_is_power_of_two(b, &ix) == 1) { if (d != NULL) { *d = a->dp[0] & ((((mp_digit)1)<<ix) - 1); } if (c != NULL) { return mp_div_2d(a, ix, c, NULL); } return MP_OKAY; } /* no easy answer [c'est la vie]. Just division */ if ((res = mp_init_size(&q, a->used)) != MP_OKAY) { return res; } q.used = a->used; q.sign = a->sign; w = 0; for (ix = a->used - 1; ix >= 0; ix--) { w = (w << ((mp_word)DIGIT_BIT)) | ((mp_word)a->dp[ix]); if (w >= b) { t = (mp_digit)(w / b); w -= ((mp_word)t) * ((mp_word)b); } else { t = 0; } q.dp[ix] = (mp_digit)t; } if (d != NULL) { *d = (mp_digit)w; } if (c != NULL) { mp_clamp(&q); mp_exch(&q, c); } mp_clear(&q); return res; } /* reduce "x" in place modulo "n" using the Diminished Radix algorithm. * * Based on algorithm from the paper * * "Generating Efficient Primes for Discrete Log Cryptosystems" * Chae Hoon Lim, Pil Loong Lee, * POSTECH Information Research Laboratories * * The modulus must be of a special format [see manual] * * Has been modified to use algorithm 7.10 from the LTM book instead * * Input x must be in the range 0 <= x <= (n-1)**2 */ int mp_dr_reduce (mp_int * x, mp_int * n, mp_digit k) { int err, i, m; mp_word r; mp_digit mu, *tmpx1, *tmpx2; /* m = digits in modulus */ m = n->used; /* ensure that "x" has at least 2m digits */ if (x->alloc < m + m) { if ((err = mp_grow (x, m + m)) != MP_OKAY) { return err; } } /* top of loop, this is where the code resumes if * another reduction pass is required. */ top: /* aliases for digits */ /* alias for lower half of x */ tmpx1 = x->dp; /* alias for upper half of x, or x/B**m */ tmpx2 = x->dp + m; /* set carry to zero */ mu = 0; /* compute (x mod B**m) + k * [x/B**m] inline and inplace */ for (i = 0; i < m; i++) { r = ((mp_word)*tmpx2++) * ((mp_word)k) + *tmpx1 + mu; *tmpx1++ = (mp_digit)(r & MP_MASK); mu = (mp_digit)(r >> ((mp_word)DIGIT_BIT)); } /* set final carry */ *tmpx1++ = mu; /* zero words above m */ for (i = m + 1; i < x->used; i++) { *tmpx1++ = 0; } /* clamp, sub and return */ mp_clamp (x); /* if x >= n then subtract and reduce again * Each successive "recursion" makes the input smaller and smaller. */ if (mp_cmp_mag (x, n) != MP_LT) { s_mp_sub(x, n, x); goto top; } return MP_OKAY; } /* determines the setup value */ void mp_dr_setup(mp_int *a, mp_digit *d) { /* the casts are required if DIGIT_BIT is one less than * the number of bits in a mp_digit [e.g. DIGIT_BIT==31] */ *d = (mp_digit)((((mp_word)1) << ((mp_word)DIGIT_BIT)) - ((mp_word)a->dp[0])); } /* swap the elements of two integers, for cases where you can't simply swap the * mp_int pointers around */ void mp_exch (mp_int * a, mp_int * b) { mp_int t; t = *a; *a = *b; *b = t; } /* this is a shell function that calls either the normal or Montgomery * exptmod functions. Originally the call to the montgomery code was * embedded in the normal function but that wasted a lot of stack space * for nothing (since 99% of the time the Montgomery code would be called) */ int mp_exptmod (mp_int * G, mp_int * X, mp_int * P, mp_int * Y) { int dr; /* modulus P must be positive */ if (P->sign == MP_NEG) { return MP_VAL; } /* if exponent X is negative we have to recurse */ if (X->sign == MP_NEG) { mp_int tmpG, tmpX; int err; /* first compute 1/G mod P */ if ((err = mp_init(&tmpG)) != MP_OKAY) { return err; } if ((err = mp_invmod(G, P, &tmpG)) != MP_OKAY) { mp_clear(&tmpG); return err; } /* now get |X| */ if ((err = mp_init(&tmpX)) != MP_OKAY) { mp_clear(&tmpG); return err; } if ((err = mp_abs(X, &tmpX)) != MP_OKAY) { mp_clear_multi(&tmpG, &tmpX, NULL); return err; } /* and now compute (1/G)**|X| instead of G**X [X < 0] */ err = mp_exptmod(&tmpG, &tmpX, P, Y); mp_clear_multi(&tmpG, &tmpX, NULL); return err; } dr = 0; /* if the modulus is odd or dr != 0 use the fast method */ if (mp_isodd (P) == 1 || dr != 0) { return mp_exptmod_fast (G, X, P, Y, dr); } else { /* otherwise use the generic Barrett reduction technique */ return s_mp_exptmod (G, X, P, Y); } } /* computes Y == G**X mod P, HAC pp.616, Algorithm 14.85 * * Uses a left-to-right k-ary sliding window to compute the modular exponentiation. * The value of k changes based on the size of the exponent. * * Uses Montgomery or Diminished Radix reduction [whichever appropriate] */ int mp_exptmod_fast (mp_int * G, mp_int * X, mp_int * P, mp_int * Y, int redmode) { mp_int M[256], res; mp_digit buf, mp; int err, bitbuf, bitcpy, bitcnt, mode, digidx, x, y, winsize; /* use a pointer to the reduction algorithm. This allows us to use * one of many reduction algorithms without modding the guts of * the code with if statements everywhere. */ int (*redux)(mp_int*,mp_int*,mp_digit); /* find window size */ x = mp_count_bits (X); if (x <= 7) { winsize = 2; } else if (x <= 36) { winsize = 3; } else if (x <= 140) { winsize = 4; } else if (x <= 450) { winsize = 5; } else if (x <= 1303) { winsize = 6; } else if (x <= 3529) { winsize = 7; } else { winsize = 8; } /* init M array */ /* init first cell */ if ((err = mp_init(&M[1])) != MP_OKAY) { return err; } /* now init the second half of the array */ for (x = 1<<(winsize-1); x < (1 << winsize); x++) { if ((err = mp_init(&M[x])) != MP_OKAY) { for (y = 1<<(winsize-1); y < x; y++) { mp_clear (&M[y]); } mp_clear(&M[1]); return err; } } /* determine and setup reduction code */ if (redmode == 0) { /* now setup montgomery */ if ((err = mp_montgomery_setup (P, &mp)) != MP_OKAY) { goto __M; } /* automatically pick the comba one if available (saves quite a few calls/ifs) */ if (((P->used * 2 + 1) < MP_WARRAY) && P->used < (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) { redux = fast_mp_montgomery_reduce; } else { /* use slower baseline Montgomery method */ redux = mp_montgomery_reduce; } } else if (redmode == 1) { /* setup DR reduction for moduli of the form B**k - b */ mp_dr_setup(P, &mp); redux = mp_dr_reduce; } else { /* setup DR reduction for moduli of the form 2**k - b */ if ((err = mp_reduce_2k_setup(P, &mp)) != MP_OKAY) { goto __M; } redux = mp_reduce_2k; } /* setup result */ if ((err = mp_init (&res)) != MP_OKAY) { goto __M; } /* create M table * * * The first half of the table is not computed though accept for M[0] and M[1] */ if (redmode == 0) { /* now we need R mod m */ if ((err = mp_montgomery_calc_normalization (&res, P)) != MP_OKAY) { goto __RES; } /* now set M[1] to G * R mod m */ if ((err = mp_mulmod (G, &res, P, &M[1])) != MP_OKAY) { goto __RES; } } else { mp_set(&res, 1); if ((err = mp_mod(G, P, &M[1])) != MP_OKAY) { goto __RES; } } /* compute the value at M[1<<(winsize-1)] by squaring M[1] (winsize-1) times */ if ((err = mp_copy (&M[1], &M[1 << (winsize - 1)])) != MP_OKAY) { goto __RES; } for (x = 0; x < (winsize - 1); x++) { if ((err = mp_sqr (&M[1 << (winsize - 1)], &M[1 << (winsize - 1)])) != MP_OKAY) { goto __RES; } if ((err = redux (&M[1 << (winsize - 1)], P, mp)) != MP_OKAY) { goto __RES; } } /* create upper table */ for (x = (1 << (winsize - 1)) + 1; x < (1 << winsize); x++) { if ((err = mp_mul (&M[x - 1], &M[1], &M[x])) != MP_OKAY) { goto __RES; } if ((err = redux (&M[x], P, mp)) != MP_OKAY) { goto __RES; } } /* set initial mode and bit cnt */ mode = 0; bitcnt = 1; buf = 0; digidx = X->used - 1; bitcpy = 0; bitbuf = 0; for (;;) { /* grab next digit as required */ if (--bitcnt == 0) { /* if digidx == -1 we are out of digits so break */ if (digidx == -1) { break; } /* read next digit and reset bitcnt */ buf = X->dp[digidx--]; bitcnt = (int)DIGIT_BIT; } /* grab the next msb from the exponent */ y = (mp_digit)(buf >> (DIGIT_BIT - 1)) & 1; buf <<= (mp_digit)1; /* if the bit is zero and mode == 0 then we ignore it * These represent the leading zero bits before the first 1 bit * in the exponent. Technically this opt is not required but it * does lower the # of trivial squaring/reductions used */ if (mode == 0 && y == 0) { continue; } /* if the bit is zero and mode == 1 then we square */ if (mode == 1 && y == 0) { if ((err = mp_sqr (&res, &res)) != MP_OKAY) { goto __RES; } if ((err = redux (&res, P, mp)) != MP_OKAY) { goto __RES; } continue; } /* else we add it to the window */ bitbuf |= (y << (winsize - ++bitcpy)); mode = 2; if (bitcpy == winsize) { /* ok window is filled so square as required and multiply */ /* square first */ for (x = 0; x < winsize; x++) { if ((err = mp_sqr (&res, &res)) != MP_OKAY) { goto __RES; } if ((err = redux (&res, P, mp)) != MP_OKAY) { goto __RES; } } /* then multiply */ if ((err = mp_mul (&res, &M[bitbuf], &res)) != MP_OKAY) { goto __RES; } if ((err = redux (&res, P, mp)) != MP_OKAY) { goto __RES; } /* empty window and reset */ bitcpy = 0; bitbuf = 0; mode = 1; } } /* if bits remain then square/multiply */ if (mode == 2 && bitcpy > 0) { /* square then multiply if the bit is set */ for (x = 0; x < bitcpy; x++) { if ((err = mp_sqr (&res, &res)) != MP_OKAY) { goto __RES; } if ((err = redux (&res, P, mp)) != MP_OKAY) { goto __RES; } /* get next bit of the window */ bitbuf <<= 1; if ((bitbuf & (1 << winsize)) != 0) { /* then multiply */ if ((err = mp_mul (&res, &M[1], &res)) != MP_OKAY) { goto __RES; } if ((err = redux (&res, P, mp)) != MP_OKAY) { goto __RES; } } } } if (redmode == 0) { /* fixup result if Montgomery reduction is used * recall that any value in a Montgomery system is * actually multiplied by R mod n. So we have * to reduce one more time to cancel out the factor * of R. */ if ((err = redux(&res, P, mp)) != MP_OKAY) { goto __RES; } } /* swap res with Y */ mp_exch (&res, Y); err = MP_OKAY; __RES:mp_clear (&res); __M: mp_clear(&M[1]); for (x = 1<<(winsize-1); x < (1 << winsize); x++) { mp_clear (&M[x]); } return err; } /* Greatest Common Divisor using the binary method */ int mp_gcd (mp_int * a, mp_int * b, mp_int * c) { mp_int u, v; int k, u_lsb, v_lsb, res; /* either zero than gcd is the largest */ if (mp_iszero (a) == 1 && mp_iszero (b) == 0) { return mp_abs (b, c); } if (mp_iszero (a) == 0 && mp_iszero (b) == 1) { return mp_abs (a, c); } /* optimized. At this point if a == 0 then * b must equal zero too */ if (mp_iszero (a) == 1) { mp_zero(c); return MP_OKAY; } /* get copies of a and b we can modify */ if ((res = mp_init_copy (&u, a)) != MP_OKAY) { return res; } if ((res = mp_init_copy (&v, b)) != MP_OKAY) { goto __U; } /* must be positive for the remainder of the algorithm */ u.sign = v.sign = MP_ZPOS; /* B1. Find the common power of two for u and v */ u_lsb = mp_cnt_lsb(&u); v_lsb = mp_cnt_lsb(&v); k = MIN(u_lsb, v_lsb); if (k > 0) { /* divide the power of two out */ if ((res = mp_div_2d(&u, k, &u, NULL)) != MP_OKAY) { goto __V; } if ((res = mp_div_2d(&v, k, &v, NULL)) != MP_OKAY) { goto __V; } } /* divide any remaining factors of two out */ if (u_lsb != k) { if ((res = mp_div_2d(&u, u_lsb - k, &u, NULL)) != MP_OKAY) { goto __V; } } if (v_lsb != k) { if ((res = mp_div_2d(&v, v_lsb - k, &v, NULL)) != MP_OKAY) { goto __V; } } while (mp_iszero(&v) == 0) { /* make sure v is the largest */ if (mp_cmp_mag(&u, &v) == MP_GT) { /* swap u and v to make sure v is >= u */ mp_exch(&u, &v); } /* subtract smallest from largest */ if ((res = s_mp_sub(&v, &u, &v)) != MP_OKAY) { goto __V; } /* Divide out all factors of two */ if ((res = mp_div_2d(&v, mp_cnt_lsb(&v), &v, NULL)) != MP_OKAY) { goto __V; } } /* multiply by 2**k which we divided out at the beginning */ if ((res = mp_mul_2d (&u, k, c)) != MP_OKAY) { goto __V; } c->sign = MP_ZPOS; res = MP_OKAY; __V:mp_clear (&u); __U:mp_clear (&v); return res; } /* get the lower 32-bits of an mp_int */ unsigned long mp_get_int(mp_int * a) { int i; unsigned long res; if (a->used == 0) { return 0; } /* get number of digits of the lsb we have to read */ i = MIN(a->used,(int)((sizeof(unsigned long)*CHAR_BIT+DIGIT_BIT-1)/DIGIT_BIT))-1; /* get most significant digit of result */ res = DIGIT(a,i); while (--i >= 0) { res = (res << DIGIT_BIT) | DIGIT(a,i); } /* force result to 32-bits always so it is consistent on non 32-bit platforms */ return res & 0xFFFFFFFFUL; } /* grow as required */ int mp_grow (mp_int * a, int size) { int i; mp_digit *tmp; /* if the alloc size is smaller alloc more ram */ if (a->alloc < size) { /* ensure there are always at least MP_PREC digits extra on top */ size += (MP_PREC * 2) - (size % MP_PREC); /* reallocate the array a->dp * * We store the return in a temporary variable * in case the operation failed we don't want * to overwrite the dp member of a. */ tmp = realloc (a->dp, sizeof (mp_digit) * size); if (tmp == NULL) { /* reallocation failed but "a" is still valid [can be freed] */ return MP_MEM; } /* reallocation succeeded so set a->dp */ a->dp = tmp; /* zero excess digits */ i = a->alloc; a->alloc = size; for (; i < a->alloc; i++) { a->dp[i] = 0; } } return MP_OKAY; } /* init a new mp_int */ int mp_init (mp_int * a) { int i; /* allocate memory required and clear it */ a->dp = malloc (sizeof (mp_digit) * MP_PREC); if (a->dp == NULL) { return MP_MEM; } /* set the digits to zero */ for (i = 0; i < MP_PREC; i++) { a->dp[i] = 0; } /* set the used to zero, allocated digits to the default precision * and sign to positive */ a->used = 0; a->alloc = MP_PREC; a->sign = MP_ZPOS; return MP_OKAY; } /* creates "a" then copies b into it */ int mp_init_copy (mp_int * a, const mp_int * b) { int res; if ((res = mp_init (a)) != MP_OKAY) { return res; } return mp_copy (b, a); } int mp_init_multi(mp_int *mp, ...) { mp_err res = MP_OKAY; /* Assume ok until proven otherwise */ int n = 0; /* Number of ok inits */ mp_int* cur_arg = mp; va_list args; va_start(args, mp); /* init args to next argument from caller */ while (cur_arg != NULL) { if (mp_init(cur_arg) != MP_OKAY) { /* Oops - error! Back-track and mp_clear what we already succeeded in init-ing, then return error. */ va_list clean_args; /* end the current list */ va_end(args); /* now start cleaning up */ cur_arg = mp; va_start(clean_args, mp); while (n--) { mp_clear(cur_arg); cur_arg = va_arg(clean_args, mp_int*); } va_end(clean_args); res = MP_MEM; break; } n++; cur_arg = va_arg(args, mp_int*); } va_end(args); return res; /* Assumed ok, if error flagged above. */ } /* init an mp_init for a given size */ int mp_init_size (mp_int * a, int size) { int x; /* pad size so there are always extra digits */ size += (MP_PREC * 2) - (size % MP_PREC); /* alloc mem */ a->dp = malloc (sizeof (mp_digit) * size); if (a->dp == NULL) { return MP_MEM; } /* set the members */ a->used = 0; a->alloc = size; a->sign = MP_ZPOS; /* zero the digits */ for (x = 0; x < size; x++) { a->dp[x] = 0; } return MP_OKAY; } /* hac 14.61, pp608 */ int mp_invmod (mp_int * a, mp_int * b, mp_int * c) { /* b cannot be negative */ if (b->sign == MP_NEG || mp_iszero(b) == 1) { return MP_VAL; } /* if the modulus is odd we can use a faster routine instead */ if (mp_isodd (b) == 1) { return fast_mp_invmod (a, b, c); } return mp_invmod_slow(a, b, c); } /* hac 14.61, pp608 */ int mp_invmod_slow (mp_int * a, mp_int * b, mp_int * c) { mp_int x, y, u, v, A, B, C, D; int res; /* b cannot be negative */ if (b->sign == MP_NEG || mp_iszero(b) == 1) { return MP_VAL; } /* init temps */ if ((res = mp_init_multi(&x, &y, &u, &v, &A, &B, &C, &D, NULL)) != MP_OKAY) { return res; } /* x = a, y = b */ if ((res = mp_copy (a, &x)) != MP_OKAY) { goto __ERR; } if ((res = mp_copy (b, &y)) != MP_OKAY) { goto __ERR; } /* 2. [modified] if x,y are both even then return an error! */ if (mp_iseven (&x) == 1 && mp_iseven (&y) == 1) { res = MP_VAL; goto __ERR; } /* 3. u=x, v=y, A=1, B=0, C=0,D=1 */ if ((res = mp_copy (&x, &u)) != MP_OKAY) { goto __ERR; } if ((res = mp_copy (&y, &v)) != MP_OKAY) { goto __ERR; } mp_set (&A, 1); mp_set (&D, 1); top: /* 4. while u is even do */ while (mp_iseven (&u) == 1) { /* 4.1 u = u/2 */ if ((res = mp_div_2 (&u, &u)) != MP_OKAY) { goto __ERR; } /* 4.2 if A or B is odd then */ if (mp_isodd (&A) == 1 || mp_isodd (&B) == 1) { /* A = (A+y)/2, B = (B-x)/2 */ if ((res = mp_add (&A, &y, &A)) != MP_OKAY) { goto __ERR; } if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) { goto __ERR; } } /* A = A/2, B = B/2 */ if ((res = mp_div_2 (&A, &A)) != MP_OKAY) { goto __ERR; } if ((res = mp_div_2 (&B, &B)) != MP_OKAY) { goto __ERR; } } /* 5. while v is even do */ while (mp_iseven (&v) == 1) { /* 5.1 v = v/2 */ if ((res = mp_div_2 (&v, &v)) != MP_OKAY) { goto __ERR; } /* 5.2 if C or D is odd then */ if (mp_isodd (&C) == 1 || mp_isodd (&D) == 1) { /* C = (C+y)/2, D = (D-x)/2 */ if ((res = mp_add (&C, &y, &C)) != MP_OKAY) { goto __ERR; } if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) { goto __ERR; } } /* C = C/2, D = D/2 */ if ((res = mp_div_2 (&C, &C)) != MP_OKAY) { goto __ERR; } if ((res = mp_div_2 (&D, &D)) != MP_OKAY) { goto __ERR; } } /* 6. if u >= v then */ if (mp_cmp (&u, &v) != MP_LT) { /* u = u - v, A = A - C, B = B - D */ if ((res = mp_sub (&u, &v, &u)) != MP_OKAY) { goto __ERR; } if ((res = mp_sub (&A, &C, &A)) != MP_OKAY) { goto __ERR; } if ((res = mp_sub (&B, &D, &B)) != MP_OKAY) { goto __ERR; } } else { /* v - v - u, C = C - A, D = D - B */ if ((res = mp_sub (&v, &u, &v)) != MP_OKAY) { goto __ERR; } if ((res = mp_sub (&C, &A, &C)) != MP_OKAY) { goto __ERR; } if ((res = mp_sub (&D, &B, &D)) != MP_OKAY) { goto __ERR; } } /* if not zero goto step 4 */ if (mp_iszero (&u) == 0) goto top; /* now a = C, b = D, gcd == g*v */ /* if v != 1 then there is no inverse */ if (mp_cmp_d (&v, 1) != MP_EQ) { res = MP_VAL; goto __ERR; } /* if its too low */ while (mp_cmp_d(&C, 0) == MP_LT) { if ((res = mp_add(&C, b, &C)) != MP_OKAY) { goto __ERR; } } /* too big */ while (mp_cmp_mag(&C, b) != MP_LT) { if ((res = mp_sub(&C, b, &C)) != MP_OKAY) { goto __ERR; } } /* C is now the inverse */ mp_exch (&C, c); res = MP_OKAY; __ERR:mp_clear_multi (&x, &y, &u, &v, &A, &B, &C, &D, NULL); return res; } /* c = |a| * |b| using Karatsuba Multiplication using * three half size multiplications * * Let B represent the radix [e.g. 2**DIGIT_BIT] and * let n represent half of the number of digits in * the min(a,b) * * a = a1 * B**n + a0 * b = b1 * B**n + b0 * * Then, a * b => a1b1 * B**2n + ((a1 - a0)(b1 - b0) + a0b0 + a1b1) * B + a0b0 * * Note that a1b1 and a0b0 are used twice and only need to be * computed once. So in total three half size (half # of * digit) multiplications are performed, a0b0, a1b1 and * (a1-b1)(a0-b0) * * Note that a multiplication of half the digits requires * 1/4th the number of single precision multiplications so in * total after one call 25% of the single precision multiplications * are saved. Note also that the call to mp_mul can end up back * in this function if the a0, a1, b0, or b1 are above the threshold. * This is known as divide-and-conquer and leads to the famous * O(N**lg(3)) or O(N**1.584) work which is asymptopically lower than * the standard O(N**2) that the baseline/comba methods use. * Generally though the overhead of this method doesn't pay off * until a certain size (N ~ 80) is reached. */ int mp_karatsuba_mul (mp_int * a, mp_int * b, mp_int * c) { mp_int x0, x1, y0, y1, t1, x0y0, x1y1; int B, err; /* default the return code to an error */ err = MP_MEM; /* min # of digits */ B = MIN (a->used, b->used); /* now divide in two */ B = B >> 1; /* init copy all the temps */ if (mp_init_size (&x0, B) != MP_OKAY) goto ERR; if (mp_init_size (&x1, a->used - B) != MP_OKAY) goto X0; if (mp_init_size (&y0, B) != MP_OKAY) goto X1; if (mp_init_size (&y1, b->used - B) != MP_OKAY) goto Y0; /* init temps */ if (mp_init_size (&t1, B * 2) != MP_OKAY) goto Y1; if (mp_init_size (&x0y0, B * 2) != MP_OKAY) goto T1; if (mp_init_size (&x1y1, B * 2) != MP_OKAY) goto X0Y0; /* now shift the digits */ x0.used = y0.used = B; x1.used = a->used - B; y1.used = b->used - B; { register int x; register mp_digit *tmpa, *tmpb, *tmpx, *tmpy; /* we copy the digits directly instead of using higher level functions * since we also need to shift the digits */ tmpa = a->dp; tmpb = b->dp; tmpx = x0.dp; tmpy = y0.dp; for (x = 0; x < B; x++) { *tmpx++ = *tmpa++; *tmpy++ = *tmpb++; } tmpx = x1.dp; for (x = B; x < a->used; x++) { *tmpx++ = *tmpa++; } tmpy = y1.dp; for (x = B; x < b->used; x++) { *tmpy++ = *tmpb++; } } /* only need to clamp the lower words since by definition the * upper words x1/y1 must have a known number of digits */ mp_clamp (&x0); mp_clamp (&y0); /* now calc the products x0y0 and x1y1 */ /* after this x0 is no longer required, free temp [x0==t2]! */ if (mp_mul (&x0, &y0, &x0y0) != MP_OKAY) goto X1Y1; /* x0y0 = x0*y0 */ if (mp_mul (&x1, &y1, &x1y1) != MP_OKAY) goto X1Y1; /* x1y1 = x1*y1 */ /* now calc x1-x0 and y1-y0 */ if (mp_sub (&x1, &x0, &t1) != MP_OKAY) goto X1Y1; /* t1 = x1 - x0 */ if (mp_sub (&y1, &y0, &x0) != MP_OKAY) goto X1Y1; /* t2 = y1 - y0 */ if (mp_mul (&t1, &x0, &t1) != MP_OKAY) goto X1Y1; /* t1 = (x1 - x0) * (y1 - y0) */ /* add x0y0 */ if (mp_add (&x0y0, &x1y1, &x0) != MP_OKAY) goto X1Y1; /* t2 = x0y0 + x1y1 */ if (mp_sub (&x0, &t1, &t1) != MP_OKAY) goto X1Y1; /* t1 = x0y0 + x1y1 - (x1-x0)*(y1-y0) */ /* shift by B */ if (mp_lshd (&t1, B) != MP_OKAY) goto X1Y1; /* t1 = (x0y0 + x1y1 - (x1-x0)*(y1-y0))<<B */ if (mp_lshd (&x1y1, B * 2) != MP_OKAY) goto X1Y1; /* x1y1 = x1y1 << 2*B */ if (mp_add (&x0y0, &t1, &t1) != MP_OKAY) goto X1Y1; /* t1 = x0y0 + t1 */ if (mp_add (&t1, &x1y1, c) != MP_OKAY) goto X1Y1; /* t1 = x0y0 + t1 + x1y1 */ /* Algorithm succeeded set the return code to MP_OKAY */ err = MP_OKAY; X1Y1:mp_clear (&x1y1); X0Y0:mp_clear (&x0y0); T1:mp_clear (&t1); Y1:mp_clear (&y1); Y0:mp_clear (&y0); X1:mp_clear (&x1); X0:mp_clear (&x0); ERR: return err; } /* Karatsuba squaring, computes b = a*a using three * half size squarings * * See comments of karatsuba_mul for details. It * is essentially the same algorithm but merely * tuned to perform recursive squarings. */ int mp_karatsuba_sqr (mp_int * a, mp_int * b) { mp_int x0, x1, t1, t2, x0x0, x1x1; int B, err; err = MP_MEM; /* min # of digits */ B = a->used; /* now divide in two */ B = B >> 1; /* init copy all the temps */ if (mp_init_size (&x0, B) != MP_OKAY) goto ERR; if (mp_init_size (&x1, a->used - B) != MP_OKAY) goto X0; /* init temps */ if (mp_init_size (&t1, a->used * 2) != MP_OKAY) goto X1; if (mp_init_size (&t2, a->used * 2) != MP_OKAY) goto T1; if (mp_init_size (&x0x0, B * 2) != MP_OKAY) goto T2; if (mp_init_size (&x1x1, (a->used - B) * 2) != MP_OKAY) goto X0X0; { register int x; register mp_digit *dst, *src; src = a->dp; /* now shift the digits */ dst = x0.dp; for (x = 0; x < B; x++) { *dst++ = *src++; } dst = x1.dp; for (x = B; x < a->used; x++) { *dst++ = *src++; } } x0.used = B; x1.used = a->used - B; mp_clamp (&x0); /* now calc the products x0*x0 and x1*x1 */ if (mp_sqr (&x0, &x0x0) != MP_OKAY) goto X1X1; /* x0x0 = x0*x0 */ if (mp_sqr (&x1, &x1x1) != MP_OKAY) goto X1X1; /* x1x1 = x1*x1 */ /* now calc (x1-x0)**2 */ if (mp_sub (&x1, &x0, &t1) != MP_OKAY) goto X1X1; /* t1 = x1 - x0 */ if (mp_sqr (&t1, &t1) != MP_OKAY) goto X1X1; /* t1 = (x1 - x0) * (x1 - x0) */ /* add x0y0 */ if (s_mp_add (&x0x0, &x1x1, &t2) != MP_OKAY) goto X1X1; /* t2 = x0x0 + x1x1 */ if (mp_sub (&t2, &t1, &t1) != MP_OKAY) goto X1X1; /* t1 = x0x0 + x1x1 - (x1-x0)*(x1-x0) */ /* shift by B */ if (mp_lshd (&t1, B) != MP_OKAY) goto X1X1; /* t1 = (x0x0 + x1x1 - (x1-x0)*(x1-x0))<<B */ if (mp_lshd (&x1x1, B * 2) != MP_OKAY) goto X1X1; /* x1x1 = x1x1 << 2*B */ if (mp_add (&x0x0, &t1, &t1) != MP_OKAY) goto X1X1; /* t1 = x0x0 + t1 */ if (mp_add (&t1, &x1x1, b) != MP_OKAY) goto X1X1; /* t1 = x0x0 + t1 + x1x1 */ err = MP_OKAY; X1X1:mp_clear (&x1x1); X0X0:mp_clear (&x0x0); T2:mp_clear (&t2); T1:mp_clear (&t1); X1:mp_clear (&x1); X0:mp_clear (&x0); ERR: return err; } /* computes least common multiple as |a*b|/(a, b) */ int mp_lcm (mp_int * a, mp_int * b, mp_int * c) { int res; mp_int t1, t2; if ((res = mp_init_multi (&t1, &t2, NULL)) != MP_OKAY) { return res; } /* t1 = get the GCD of the two inputs */ if ((res = mp_gcd (a, b, &t1)) != MP_OKAY) { goto __T; } /* divide the smallest by the GCD */ if (mp_cmp_mag(a, b) == MP_LT) { /* store quotient in t2 such that t2 * b is the LCM */ if ((res = mp_div(a, &t1, &t2, NULL)) != MP_OKAY) { goto __T; } res = mp_mul(b, &t2, c); } else { /* store quotient in t2 such that t2 * a is the LCM */ if ((res = mp_div(b, &t1, &t2, NULL)) != MP_OKAY) { goto __T; } res = mp_mul(a, &t2, c); } /* fix the sign to positive */ c->sign = MP_ZPOS; __T: mp_clear_multi (&t1, &t2, NULL); return res; } /* shift left a certain amount of digits */ int mp_lshd (mp_int * a, int b) { int x, res; /* if its less than zero return */ if (b <= 0) { return MP_OKAY; } /* grow to fit the new digits */ if (a->alloc < a->used + b) { if ((res = mp_grow (a, a->used + b)) != MP_OKAY) { return res; } } { register mp_digit *top, *bottom; /* increment the used by the shift amount then copy upwards */ a->used += b; /* top */ top = a->dp + a->used - 1; /* base */ bottom = a->dp + a->used - 1 - b; /* much like mp_rshd this is implemented using a sliding window * except the window goes the otherway around. Copying from * the bottom to the top. see bn_mp_rshd.c for more info. */ for (x = a->used - 1; x >= b; x--) { *top-- = *bottom--; } /* zero the lower digits */ top = a->dp; for (x = 0; x < b; x++) { *top++ = 0; } } return MP_OKAY; } /* c = a mod b, 0 <= c < b */ int mp_mod (mp_int * a, mp_int * b, mp_int * c) { mp_int t; int res; if ((res = mp_init (&t)) != MP_OKAY) { return res; } if ((res = mp_div (a, b, NULL, &t)) != MP_OKAY) { mp_clear (&t); return res; } if (t.sign != b->sign) { res = mp_add (b, &t, c); } else { res = MP_OKAY; mp_exch (&t, c); } mp_clear (&t); return res; } /* calc a value mod 2**b */ int mp_mod_2d (mp_int * a, int b, mp_int * c) { int x, res; /* if b is <= 0 then zero the int */ if (b <= 0) { mp_zero (c); return MP_OKAY; } /* if the modulus is larger than the value than return */ if (b > (int) (a->used * DIGIT_BIT)) { res = mp_copy (a, c); return res; } /* copy */ if ((res = mp_copy (a, c)) != MP_OKAY) { return res; } /* zero digits above the last digit of the modulus */ for (x = (b / DIGIT_BIT) + ((b % DIGIT_BIT) == 0 ? 0 : 1); x < c->used; x++) { c->dp[x] = 0; } /* clear the digit that is not completely outside/inside the modulus */ c->dp[b / DIGIT_BIT] &= (mp_digit) ((((mp_digit) 1) << (((mp_digit) b) % DIGIT_BIT)) - ((mp_digit) 1)); mp_clamp (c); return MP_OKAY; } int mp_mod_d (mp_int * a, mp_digit b, mp_digit * c) { return mp_div_d(a, b, NULL, c); } /* * shifts with subtractions when the result is greater than b. * * The method is slightly modified to shift B unconditionally up to just under * the leading bit of b. This saves a lot of multiple precision shifting. */ int mp_montgomery_calc_normalization (mp_int * a, mp_int * b) { int x, bits, res; /* how many bits of last digit does b use */ bits = mp_count_bits (b) % DIGIT_BIT; if (b->used > 1) { if ((res = mp_2expt (a, (b->used - 1) * DIGIT_BIT + bits - 1)) != MP_OKAY) { return res; } } else { mp_set(a, 1); bits = 1; } /* now compute C = A * B mod b */ for (x = bits - 1; x < (int)DIGIT_BIT; x++) { if ((res = mp_mul_2 (a, a)) != MP_OKAY) { return res; } if (mp_cmp_mag (a, b) != MP_LT) { if ((res = s_mp_sub (a, b, a)) != MP_OKAY) { return res; } } } return MP_OKAY; } /* computes xR**-1 == x (mod N) via Montgomery Reduction */ int mp_montgomery_reduce (mp_int * x, mp_int * n, mp_digit rho) { int ix, res, digs; mp_digit mu; /* can the fast reduction [comba] method be used? * * Note that unlike in mul you're safely allowed *less* * than the available columns [255 per default] since carries * are fixed up in the inner loop. */ digs = n->used * 2 + 1; if ((digs < MP_WARRAY) && n->used < (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) { return fast_mp_montgomery_reduce (x, n, rho); } /* grow the input as required */ if (x->alloc < digs) { if ((res = mp_grow (x, digs)) != MP_OKAY) { return res; } } x->used = digs; for (ix = 0; ix < n->used; ix++) { /* mu = ai * rho mod b * * The value of rho must be precalculated via * montgomery_setup() such that * it equals -1/n0 mod b this allows the * following inner loop to reduce the * input one digit at a time */ mu = (mp_digit) (((mp_word)x->dp[ix]) * ((mp_word)rho) & MP_MASK); /* a = a + mu * m * b**i */ { register int iy; register mp_digit *tmpn, *tmpx, u; register mp_word r; /* alias for digits of the modulus */ tmpn = n->dp; /* alias for the digits of x [the input] */ tmpx = x->dp + ix; /* set the carry to zero */ u = 0; /* Multiply and add in place */ for (iy = 0; iy < n->used; iy++) { /* compute product and sum */ r = ((mp_word)mu) * ((mp_word)*tmpn++) + ((mp_word) u) + ((mp_word) * tmpx); /* get carry */ u = (mp_digit)(r >> ((mp_word) DIGIT_BIT)); /* fix digit */ *tmpx++ = (mp_digit)(r & ((mp_word) MP_MASK)); } /* At this point the ix'th digit of x should be zero */ /* propagate carries upwards as required*/ while (u) { *tmpx += u; u = *tmpx >> DIGIT_BIT; *tmpx++ &= MP_MASK; } } } /* at this point the n.used'th least * significant digits of x are all zero * which means we can shift x to the * right by n.used digits and the * residue is unchanged. */ /* x = x/b**n.used */ mp_clamp(x); mp_rshd (x, n->used); /* if x >= n then x = x - n */ if (mp_cmp_mag (x, n) != MP_LT) { return s_mp_sub (x, n, x); } return MP_OKAY; } /* setups the montgomery reduction stuff */ int mp_montgomery_setup (mp_int * n, mp_digit * rho) { mp_digit x, b; /* fast inversion mod 2**k * * Based on the fact that * * XA = 1 (mod 2**n) => (X(2-XA)) A = 1 (mod 2**2n) * => 2*X*A - X*X*A*A = 1 * => 2*(1) - (1) = 1 */ b = n->dp[0]; if ((b & 1) == 0) { return MP_VAL; } x = (((b + 2) & 4) << 1) + b; /* here x*a==1 mod 2**4 */ x *= 2 - b * x; /* here x*a==1 mod 2**8 */ x *= 2 - b * x; /* here x*a==1 mod 2**16 */ x *= 2 - b * x; /* here x*a==1 mod 2**32 */ /* rho = -1/m mod b */ *rho = (((mp_word)1 << ((mp_word) DIGIT_BIT)) - x) & MP_MASK; return MP_OKAY; } /* high level multiplication (handles sign) */ int mp_mul (mp_int * a, mp_int * b, mp_int * c) { int res, neg; neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG; /* use Karatsuba? */ if (MIN (a->used, b->used) >= KARATSUBA_MUL_CUTOFF) { res = mp_karatsuba_mul (a, b, c); } else { /* can we use the fast multiplier? * * The fast multiplier can be used if the output will * have less than MP_WARRAY digits and the number of * digits won't affect carry propagation */ int digs = a->used + b->used + 1; if ((digs < MP_WARRAY) && MIN(a->used, b->used) <= (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) { res = fast_s_mp_mul_digs (a, b, c, digs); } else res = s_mp_mul (a, b, c); /* uses s_mp_mul_digs */ } c->sign = (c->used > 0) ? neg : MP_ZPOS; return res; } /* b = a*2 */ int mp_mul_2(mp_int * a, mp_int * b) { int x, res, oldused; /* grow to accommodate result */ if (b->alloc < a->used + 1) { if ((res = mp_grow (b, a->used + 1)) != MP_OKAY) { return res; } } oldused = b->used; b->used = a->used; { register mp_digit r, rr, *tmpa, *tmpb; /* alias for source */ tmpa = a->dp; /* alias for dest */ tmpb = b->dp; /* carry */ r = 0; for (x = 0; x < a->used; x++) { /* get what will be the *next* carry bit from the * MSB of the current digit */ rr = *tmpa >> ((mp_digit)(DIGIT_BIT - 1)); /* now shift up this digit, add in the carry [from the previous] */ *tmpb++ = ((*tmpa++ << ((mp_digit)1)) | r) & MP_MASK; /* copy the carry that would be from the source * digit into the next iteration */ r = rr; } /* new leading digit? */ if (r != 0) { /* add a MSB which is always 1 at this point */ *tmpb = 1; ++(b->used); } /* now zero any excess digits on the destination * that we didn't write to */ tmpb = b->dp + b->used; for (x = b->used; x < oldused; x++) { *tmpb++ = 0; } } b->sign = a->sign; return MP_OKAY; } /* shift left by a certain bit count */ int mp_mul_2d (mp_int * a, int b, mp_int * c) { mp_digit d; int res; /* copy */ if (a != c) { if ((res = mp_copy (a, c)) != MP_OKAY) { return res; } } if (c->alloc < (int)(c->used + b/DIGIT_BIT + 1)) { if ((res = mp_grow (c, c->used + b / DIGIT_BIT + 1)) != MP_OKAY) { return res; } } /* shift by as many digits in the bit count */ if (b >= (int)DIGIT_BIT) { if ((res = mp_lshd (c, b / DIGIT_BIT)) != MP_OKAY) { return res; } } /* shift any bit count < DIGIT_BIT */ d = (mp_digit) (b % DIGIT_BIT); if (d != 0) { register mp_digit *tmpc, shift, mask, r, rr; register int x; /* bitmask for carries */ mask = (((mp_digit)1) << d) - 1; /* shift for msbs */ shift = DIGIT_BIT - d; /* alias */ tmpc = c->dp; /* carry */ r = 0; for (x = 0; x < c->used; x++) { /* get the higher bits of the current word */ rr = (*tmpc >> shift) & mask; /* shift the current word and OR in the carry */ *tmpc = ((*tmpc << d) | r) & MP_MASK; ++tmpc; /* set the carry to the carry bits of the current word */ r = rr; } /* set final carry */ if (r != 0) { c->dp[(c->used)++] = r; } } mp_clamp (c); return MP_OKAY; } /* multiply by a digit */ int mp_mul_d (mp_int * a, mp_digit b, mp_int * c) { mp_digit u, *tmpa, *tmpc; mp_word r; int ix, res, olduse; /* make sure c is big enough to hold a*b */ if (c->alloc < a->used + 1) { if ((res = mp_grow (c, a->used + 1)) != MP_OKAY) { return res; } } /* get the original destinations used count */ olduse = c->used; /* set the sign */ c->sign = a->sign; /* alias for a->dp [source] */ tmpa = a->dp; /* alias for c->dp [dest] */ tmpc = c->dp; /* zero carry */ u = 0; /* compute columns */ for (ix = 0; ix < a->used; ix++) { /* compute product and carry sum for this term */ r = ((mp_word) u) + ((mp_word)*tmpa++) * ((mp_word)b); /* mask off higher bits to get a single digit */ *tmpc++ = (mp_digit) (r & ((mp_word) MP_MASK)); /* send carry into next iteration */ u = (mp_digit) (r >> ((mp_word) DIGIT_BIT)); } /* store final carry [if any] */ *tmpc++ = u; /* now zero digits above the top */ while (ix++ < olduse) { *tmpc++ = 0; } /* set used count */ c->used = a->used + 1; mp_clamp(c); return MP_OKAY; } /* d = a * b (mod c) */ int mp_mulmod (mp_int * a, mp_int * b, mp_int * c, mp_int * d) { int res; mp_int t; if ((res = mp_init (&t)) != MP_OKAY) { return res; } if ((res = mp_mul (a, b, &t)) != MP_OKAY) { mp_clear (&t); return res; } res = mp_mod (&t, c, d); mp_clear (&t); return res; } /* determines if an integers is divisible by one * of the first PRIME_SIZE primes or not * * sets result to 0 if not, 1 if yes */ int mp_prime_is_divisible (mp_int * a, int *result) { int err, ix; mp_digit res; /* default to not */ *result = MP_NO; for (ix = 0; ix < PRIME_SIZE; ix++) { /* what is a mod __prime_tab[ix] */ if ((err = mp_mod_d (a, __prime_tab[ix], &res)) != MP_OKAY) { return err; } /* is the residue zero? */ if (res == 0) { *result = MP_YES; return MP_OKAY; } } return MP_OKAY; } /* performs a variable number of rounds of Miller-Rabin * * Probability of error after t rounds is no more than * * Sets result to 1 if probably prime, 0 otherwise */ int mp_prime_is_prime (mp_int * a, int t, int *result) { mp_int b; int ix, err, res; /* default to no */ *result = MP_NO; /* valid value of t? */ if (t <= 0 || t > PRIME_SIZE) { return MP_VAL; } /* is the input equal to one of the primes in the table? */ for (ix = 0; ix < PRIME_SIZE; ix++) { if (mp_cmp_d(a, __prime_tab[ix]) == MP_EQ) { *result = 1; return MP_OKAY; } } /* first perform trial division */ if ((err = mp_prime_is_divisible (a, &res)) != MP_OKAY) { return err; } /* return if it was trivially divisible */ if (res == MP_YES) { return MP_OKAY; } /* now perform the miller-rabin rounds */ if ((err = mp_init (&b)) != MP_OKAY) { return err; } for (ix = 0; ix < t; ix++) { /* set the prime */ mp_set (&b, __prime_tab[ix]); if ((err = mp_prime_miller_rabin (a, &b, &res)) != MP_OKAY) { goto __B; } if (res == MP_NO) { goto __B; } } /* passed the test */ *result = MP_YES; __B:mp_clear (&b); return err; } /* Miller-Rabin test of "a" to the base of "b" as described in * HAC pp. 139 Algorithm 4.24 * * Sets result to 0 if definitely composite or 1 if probably prime. * Randomly the chance of error is no more than 1/4 and often * very much lower. */ int mp_prime_miller_rabin (mp_int * a, mp_int * b, int *result) { mp_int n1, y, r; int s, j, err; /* default */ *result = MP_NO; /* ensure b > 1 */ if (mp_cmp_d(b, 1) != MP_GT) { return MP_VAL; } /* get n1 = a - 1 */ if ((err = mp_init_copy (&n1, a)) != MP_OKAY) { return err; } if ((err = mp_sub_d (&n1, 1, &n1)) != MP_OKAY) { goto __N1; } /* set 2**s * r = n1 */ if ((err = mp_init_copy (&r, &n1)) != MP_OKAY) { goto __N1; } /* count the number of least significant bits * which are zero */ s = mp_cnt_lsb(&r); /* now divide n - 1 by 2**s */ if ((err = mp_div_2d (&r, s, &r, NULL)) != MP_OKAY) { goto __R; } /* compute y = b**r mod a */ if ((err = mp_init (&y)) != MP_OKAY) { goto __R; } if ((err = mp_exptmod (b, &r, a, &y)) != MP_OKAY) { goto __Y; } /* if y != 1 and y != n1 do */ if (mp_cmp_d (&y, 1) != MP_EQ && mp_cmp (&y, &n1) != MP_EQ) { j = 1; /* while j <= s-1 and y != n1 */ while ((j <= (s - 1)) && mp_cmp (&y, &n1) != MP_EQ) { if ((err = mp_sqrmod (&y, a, &y)) != MP_OKAY) { goto __Y; } /* if y == 1 then composite */ if (mp_cmp_d (&y, 1) == MP_EQ) { goto __Y; } ++j; } /* if y != n1 then composite */ if (mp_cmp (&y, &n1) != MP_EQ) { goto __Y; } } /* probably prime now */ *result = MP_YES; __Y:mp_clear (&y); __R:mp_clear (&r); __N1:mp_clear (&n1); return err; } static const struct { int k, t; } sizes[] = { { 128, 28 }, { 256, 16 }, { 384, 10 }, { 512, 7 }, { 640, 6 }, { 768, 5 }, { 896, 4 }, { 1024, 4 } }; /* returns # of RM trials required for a given bit size */ int mp_prime_rabin_miller_trials(int size) { int x; for (x = 0; x < (int)(sizeof(sizes)/(sizeof(sizes[0]))); x++) { if (sizes[x].k == size) { return sizes[x].t; } else if (sizes[x].k > size) { return (x == 0) ? sizes[0].t : sizes[x - 1].t; } } return sizes[x-1].t + 1; } /* makes a truly random prime of a given size (bits), * * Flags are as follows: * * LTM_PRIME_BBS - make prime congruent to 3 mod 4 * LTM_PRIME_SAFE - make sure (p-1)/2 is prime as well (implies LTM_PRIME_BBS) * LTM_PRIME_2MSB_OFF - make the 2nd highest bit zero * LTM_PRIME_2MSB_ON - make the 2nd highest bit one * * You have to supply a callback which fills in a buffer with random bytes. "dat" is a parameter you can * have passed to the callback (e.g. a state or something). This function doesn't use "dat" itself * so it can be NULL * */ /* This is possibly the mother of all prime generation functions, muahahahahaha! */ int mp_prime_random_ex(mp_int *a, int t, int size, int flags, ltm_prime_callback cb, void *dat) { unsigned char *tmp, maskAND, maskOR_msb, maskOR_lsb; int res, err, bsize, maskOR_msb_offset; /* sanity check the input */ if (size <= 1 || t <= 0) { return MP_VAL; } /* LTM_PRIME_SAFE implies LTM_PRIME_BBS */ if (flags & LTM_PRIME_SAFE) { flags |= LTM_PRIME_BBS; } /* calc the byte size */ bsize = (size>>3)+((size&7)?1:0); /* we need a buffer of bsize bytes */ tmp = malloc(bsize); if (tmp == NULL) { return MP_MEM; } /* calc the maskAND value for the MSbyte*/ maskAND = ((size&7) == 0) ? 0xFF : (0xFF >> (8 - (size & 7))); /* calc the maskOR_msb */ maskOR_msb = 0; maskOR_msb_offset = ((size & 7) == 1) ? 1 : 0; if (flags & LTM_PRIME_2MSB_ON) { maskOR_msb |= 1 << ((size - 2) & 7); } else if (flags & LTM_PRIME_2MSB_OFF) { maskAND &= ~(1 << ((size - 2) & 7)); } /* get the maskOR_lsb */ maskOR_lsb = 0; if (flags & LTM_PRIME_BBS) { maskOR_lsb |= 3; } do { /* read the bytes */ if (cb(tmp, bsize, dat) != bsize) { err = MP_VAL; goto error; } /* work over the MSbyte */ tmp[0] &= maskAND; tmp[0] |= 1 << ((size - 1) & 7); /* mix in the maskORs */ tmp[maskOR_msb_offset] |= maskOR_msb; tmp[bsize-1] |= maskOR_lsb; /* read it in */ if ((err = mp_read_unsigned_bin(a, tmp, bsize)) != MP_OKAY) { goto error; } /* is it prime? */ if ((err = mp_prime_is_prime(a, t, &res)) != MP_OKAY) { goto error; } if (res == MP_NO) { continue; } if (flags & LTM_PRIME_SAFE) { /* see if (a-1)/2 is prime */ if ((err = mp_sub_d(a, 1, a)) != MP_OKAY) { goto error; } if ((err = mp_div_2(a, a)) != MP_OKAY) { goto error; } /* is it prime? */ if ((err = mp_prime_is_prime(a, t, &res)) != MP_OKAY) { goto error; } } } while (res == MP_NO); if (flags & LTM_PRIME_SAFE) { /* restore a to the original value */ if ((err = mp_mul_2(a, a)) != MP_OKAY) { goto error; } if ((err = mp_add_d(a, 1, a)) != MP_OKAY) { goto error; } } err = MP_OKAY; error: free(tmp); return err; } /* reads an unsigned char array, assumes the msb is stored first [big endian] */ int mp_read_unsigned_bin (mp_int * a, const unsigned char *b, int c) { int res; /* make sure there are at least two digits */ if (a->alloc < 2) { if ((res = mp_grow(a, 2)) != MP_OKAY) { return res; } } /* zero the int */ mp_zero (a); /* read the bytes in */ while (c-- > 0) { if ((res = mp_mul_2d (a, 8, a)) != MP_OKAY) { return res; } a->dp[0] |= *b++; a->used += 1; } mp_clamp (a); return MP_OKAY; } /* reduces x mod m, assumes 0 < x < m**2, mu is * precomputed via mp_reduce_setup. * From HAC pp.604 Algorithm 14.42 */ int mp_reduce (mp_int * x, mp_int * m, mp_int * mu) { mp_int q; int res, um = m->used; /* q = x */ if ((res = mp_init_copy (&q, x)) != MP_OKAY) { return res; } /* q1 = x / b**(k-1) */ mp_rshd (&q, um - 1); /* according to HAC this optimization is ok */ if (((unsigned long) um) > (((mp_digit)1) << (DIGIT_BIT - 1))) { if ((res = mp_mul (&q, mu, &q)) != MP_OKAY) { goto CLEANUP; } } else { if ((res = s_mp_mul_high_digs (&q, mu, &q, um - 1)) != MP_OKAY) { goto CLEANUP; } } /* q3 = q2 / b**(k+1) */ mp_rshd (&q, um + 1); /* x = x mod b**(k+1), quick (no division) */ if ((res = mp_mod_2d (x, DIGIT_BIT * (um + 1), x)) != MP_OKAY) { goto CLEANUP; } /* q = q * m mod b**(k+1), quick (no division) */ if ((res = s_mp_mul_digs (&q, m, &q, um + 1)) != MP_OKAY) { goto CLEANUP; } /* x = x - q */ if ((res = mp_sub (x, &q, x)) != MP_OKAY) { goto CLEANUP; } /* If x < 0, add b**(k+1) to it */ if (mp_cmp_d (x, 0) == MP_LT) { mp_set (&q, 1); if ((res = mp_lshd (&q, um + 1)) != MP_OKAY) goto CLEANUP; if ((res = mp_add (x, &q, x)) != MP_OKAY) goto CLEANUP; } /* Back off if it's too big */ while (mp_cmp (x, m) != MP_LT) { if ((res = s_mp_sub (x, m, x)) != MP_OKAY) { goto CLEANUP; } } CLEANUP: mp_clear (&q); return res; } /* reduces a modulo n where n is of the form 2**p - d */ int mp_reduce_2k(mp_int *a, mp_int *n, mp_digit d) { mp_int q; int p, res; if ((res = mp_init(&q)) != MP_OKAY) { return res; } p = mp_count_bits(n); top: /* q = a/2**p, a = a mod 2**p */ if ((res = mp_div_2d(a, p, &q, a)) != MP_OKAY) { goto ERR; } if (d != 1) { /* q = q * d */ if ((res = mp_mul_d(&q, d, &q)) != MP_OKAY) { goto ERR; } } /* a = a + q */ if ((res = s_mp_add(a, &q, a)) != MP_OKAY) { goto ERR; } if (mp_cmp_mag(a, n) != MP_LT) { s_mp_sub(a, n, a); goto top; } ERR: mp_clear(&q); return res; } /* determines the setup value */ int mp_reduce_2k_setup(mp_int *a, mp_digit *d) { int res, p; mp_int tmp; if ((res = mp_init(&tmp)) != MP_OKAY) { return res; } p = mp_count_bits(a); if ((res = mp_2expt(&tmp, p)) != MP_OKAY) { mp_clear(&tmp); return res; } if ((res = s_mp_sub(&tmp, a, &tmp)) != MP_OKAY) { mp_clear(&tmp); return res; } *d = tmp.dp[0]; mp_clear(&tmp); return MP_OKAY; } /* pre-calculate the value required for Barrett reduction * For a given modulus "b" it calulates the value required in "a" */ int mp_reduce_setup (mp_int * a, mp_int * b) { int res; if ((res = mp_2expt (a, b->used * 2 * DIGIT_BIT)) != MP_OKAY) { return res; } return mp_div (a, b, a, NULL); } /* shift right a certain amount of digits */ void mp_rshd (mp_int * a, int b) { int x; /* if b <= 0 then ignore it */ if (b <= 0) { return; } /* if b > used then simply zero it and return */ if (a->used <= b) { mp_zero (a); return; } { register mp_digit *bottom, *top; /* shift the digits down */ /* bottom */ bottom = a->dp; /* top [offset into digits] */ top = a->dp + b; /* this is implemented as a sliding window where * the window is b-digits long and digits from * the top of the window are copied to the bottom * * e.g. b-2 | b-1 | b0 | b1 | b2 | ... | bb | ----> /\ | ----> \-------------------/ ----> */ for (x = 0; x < (a->used - b); x++) { *bottom++ = *top++; } /* zero the top digits */ for (; x < a->used; x++) { *bottom++ = 0; } } /* remove excess digits */ a->used -= b; } /* set to a digit */ void mp_set (mp_int * a, mp_digit b) { mp_zero (a); a->dp[0] = b & MP_MASK; a->used = (a->dp[0] != 0) ? 1 : 0; } /* set a 32-bit const */ int mp_set_int (mp_int * a, unsigned long b) { int x, res; mp_zero (a); /* set four bits at a time */ for (x = 0; x < 8; x++) { /* shift the number up four bits */ if ((res = mp_mul_2d (a, 4, a)) != MP_OKAY) { return res; } /* OR in the top four bits of the source */ a->dp[0] |= (b >> 28) & 15; /* shift the source up to the next four bits */ b <<= 4; /* ensure that digits are not clamped off */ a->used += 1; } mp_clamp (a); return MP_OKAY; } /* shrink a bignum */ int mp_shrink (mp_int * a) { mp_digit *tmp; if (a->alloc != a->used && a->used > 0) { if ((tmp = realloc (a->dp, sizeof (mp_digit) * a->used)) == NULL) { return MP_MEM; } a->dp = tmp; a->alloc = a->used; } return MP_OKAY; } /* get the size for an signed equivalent */ int mp_signed_bin_size (mp_int * a) { return 1 + mp_unsigned_bin_size (a); } /* computes b = a*a */ int mp_sqr (mp_int * a, mp_int * b) { int res; if (a->used >= KARATSUBA_SQR_CUTOFF) { res = mp_karatsuba_sqr (a, b); } else { /* can we use the fast comba multiplier? */ if ((a->used * 2 + 1) < MP_WARRAY && a->used < (1 << (sizeof(mp_word) * CHAR_BIT - 2*DIGIT_BIT - 1))) { res = fast_s_mp_sqr (a, b); } else res = s_mp_sqr (a, b); } b->sign = MP_ZPOS; return res; } /* c = a * a (mod b) */ int mp_sqrmod (mp_int * a, mp_int * b, mp_int * c) { int res; mp_int t; if ((res = mp_init (&t)) != MP_OKAY) { return res; } if ((res = mp_sqr (a, &t)) != MP_OKAY) { mp_clear (&t); return res; } res = mp_mod (&t, b, c); mp_clear (&t); return res; } /* high level subtraction (handles signs) */ int mp_sub (mp_int * a, mp_int * b, mp_int * c) { int sa, sb, res; sa = a->sign; sb = b->sign; if (sa != sb) { /* subtract a negative from a positive, OR */ /* subtract a positive from a negative. */ /* In either case, ADD their magnitudes, */ /* and use the sign of the first number. */ c->sign = sa; res = s_mp_add (a, b, c); } else { /* subtract a positive from a positive, OR */ /* subtract a negative from a negative. */ /* First, take the difference between their */ /* magnitudes, then... */ if (mp_cmp_mag (a, b) != MP_LT) { /* Copy the sign from the first */ c->sign = sa; /* The first has a larger or equal magnitude */ res = s_mp_sub (a, b, c); } else { /* The result has the *opposite* sign from */ /* the first number. */ c->sign = (sa == MP_ZPOS) ? MP_NEG : MP_ZPOS; /* The second has a larger magnitude */ res = s_mp_sub (b, a, c); } } return res; } /* single digit subtraction */ int mp_sub_d (mp_int * a, mp_digit b, mp_int * c) { mp_digit *tmpa, *tmpc, mu; int res, ix, oldused; /* grow c as required */ if (c->alloc < a->used + 1) { if ((res = mp_grow(c, a->used + 1)) != MP_OKAY) { return res; } } /* if a is negative just do an unsigned * addition [with fudged signs] */ if (a->sign == MP_NEG) { a->sign = MP_ZPOS; res = mp_add_d(a, b, c); a->sign = c->sign = MP_NEG; return res; } /* setup regs */ oldused = c->used; tmpa = a->dp; tmpc = c->dp; /* if a <= b simply fix the single digit */ if ((a->used == 1 && a->dp[0] <= b) || a->used == 0) { if (a->used == 1) { *tmpc++ = b - *tmpa; } else { *tmpc++ = b; } ix = 1; /* negative/1digit */ c->sign = MP_NEG; c->used = 1; } else { /* positive/size */ c->sign = MP_ZPOS; c->used = a->used; /* subtract first digit */ *tmpc = *tmpa++ - b; mu = *tmpc >> (sizeof(mp_digit) * CHAR_BIT - 1); *tmpc++ &= MP_MASK; /* handle rest of the digits */ for (ix = 1; ix < a->used; ix++) { *tmpc = *tmpa++ - mu; mu = *tmpc >> (sizeof(mp_digit) * CHAR_BIT - 1); *tmpc++ &= MP_MASK; } } /* zero excess digits */ while (ix++ < oldused) { *tmpc++ = 0; } mp_clamp(c); return MP_OKAY; } /* store in unsigned [big endian] format */ int mp_to_unsigned_bin (mp_int * a, unsigned char *b) { int x, res; mp_int t; if ((res = mp_init_copy (&t, a)) != MP_OKAY) { return res; } x = 0; while (mp_iszero (&t) == 0) { b[x++] = (unsigned char) (t.dp[0] & 255); if ((res = mp_div_2d (&t, 8, &t, NULL)) != MP_OKAY) { mp_clear (&t); return res; } } bn_reverse (b, x); mp_clear (&t); return MP_OKAY; } /* get the size for an unsigned equivalent */ int mp_unsigned_bin_size (mp_int * a) { int size = mp_count_bits (a); return (size / 8 + ((size & 7) != 0 ? 1 : 0)); } /* set to zero */ void mp_zero (mp_int * a) { a->sign = MP_ZPOS; a->used = 0; memset (a->dp, 0, sizeof (mp_digit) * a->alloc); } const mp_digit __prime_tab[] = { 0x0002, 0x0003, 0x0005, 0x0007, 0x000B, 0x000D, 0x0011, 0x0013, 0x0017, 0x001D, 0x001F, 0x0025, 0x0029, 0x002B, 0x002F, 0x0035, 0x003B, 0x003D, 0x0043, 0x0047, 0x0049, 0x004F, 0x0053, 0x0059, 0x0061, 0x0065, 0x0067, 0x006B, 0x006D, 0x0071, 0x007F, 0x0083, 0x0089, 0x008B, 0x0095, 0x0097, 0x009D, 0x00A3, 0x00A7, 0x00AD, 0x00B3, 0x00B5, 0x00BF, 0x00C1, 0x00C5, 0x00C7, 0x00D3, 0x00DF, 0x00E3, 0x00E5, 0x00E9, 0x00EF, 0x00F1, 0x00FB, 0x0101, 0x0107, 0x010D, 0x010F, 0x0115, 0x0119, 0x011B, 0x0125, 0x0133, 0x0137, 0x0139, 0x013D, 0x014B, 0x0151, 0x015B, 0x015D, 0x0161, 0x0167, 0x016F, 0x0175, 0x017B, 0x017F, 0x0185, 0x018D, 0x0191, 0x0199, 0x01A3, 0x01A5, 0x01AF, 0x01B1, 0x01B7, 0x01BB, 0x01C1, 0x01C9, 0x01CD, 0x01CF, 0x01D3, 0x01DF, 0x01E7, 0x01EB, 0x01F3, 0x01F7, 0x01FD, 0x0209, 0x020B, 0x021D, 0x0223, 0x022D, 0x0233, 0x0239, 0x023B, 0x0241, 0x024B, 0x0251, 0x0257, 0x0259, 0x025F, 0x0265, 0x0269, 0x026B, 0x0277, 0x0281, 0x0283, 0x0287, 0x028D, 0x0293, 0x0295, 0x02A1, 0x02A5, 0x02AB, 0x02B3, 0x02BD, 0x02C5, 0x02CF, 0x02D7, 0x02DD, 0x02E3, 0x02E7, 0x02EF, 0x02F5, 0x02F9, 0x0301, 0x0305, 0x0313, 0x031D, 0x0329, 0x032B, 0x0335, 0x0337, 0x033B, 0x033D, 0x0347, 0x0355, 0x0359, 0x035B, 0x035F, 0x036D, 0x0371, 0x0373, 0x0377, 0x038B, 0x038F, 0x0397, 0x03A1, 0x03A9, 0x03AD, 0x03B3, 0x03B9, 0x03C7, 0x03CB, 0x03D1, 0x03D7, 0x03DF, 0x03E5, 0x03F1, 0x03F5, 0x03FB, 0x03FD, 0x0407, 0x0409, 0x040F, 0x0419, 0x041B, 0x0425, 0x0427, 0x042D, 0x043F, 0x0443, 0x0445, 0x0449, 0x044F, 0x0455, 0x045D, 0x0463, 0x0469, 0x047F, 0x0481, 0x048B, 0x0493, 0x049D, 0x04A3, 0x04A9, 0x04B1, 0x04BD, 0x04C1, 0x04C7, 0x04CD, 0x04CF, 0x04D5, 0x04E1, 0x04EB, 0x04FD, 0x04FF, 0x0503, 0x0509, 0x050B, 0x0511, 0x0515, 0x0517, 0x051B, 0x0527, 0x0529, 0x052F, 0x0551, 0x0557, 0x055D, 0x0565, 0x0577, 0x0581, 0x058F, 0x0593, 0x0595, 0x0599, 0x059F, 0x05A7, 0x05AB, 0x05AD, 0x05B3, 0x05BF, 0x05C9, 0x05CB, 0x05CF, 0x05D1, 0x05D5, 0x05DB, 0x05E7, 0x05F3, 0x05FB, 0x0607, 0x060D, 0x0611, 0x0617, 0x061F, 0x0623, 0x062B, 0x062F, 0x063D, 0x0641, 0x0647, 0x0649, 0x064D, 0x0653 }; /* reverse an array, used for radix code */ void bn_reverse (unsigned char *s, int len) { int ix, iy; unsigned char t; ix = 0; iy = len - 1; while (ix < iy) { t = s[ix]; s[ix] = s[iy]; s[iy] = t; ++ix; --iy; } } /* low level addition, based on HAC pp.594, Algorithm 14.7 */ int s_mp_add (mp_int * a, mp_int * b, mp_int * c) { mp_int *x; int olduse, res, min, max; /* find sizes, we let |a| <= |b| which means we have to sort * them. "x" will point to the input with the most digits */ if (a->used > b->used) { min = b->used; max = a->used; x = a; } else { min = a->used; max = b->used; x = b; } /* init result */ if (c->alloc < max + 1) { if ((res = mp_grow (c, max + 1)) != MP_OKAY) { return res; } } /* get old used digit count and set new one */ olduse = c->used; c->used = max + 1; { register mp_digit u, *tmpa, *tmpb, *tmpc; register int i; /* alias for digit pointers */ /* first input */ tmpa = a->dp; /* second input */ tmpb = b->dp; /* destination */ tmpc = c->dp; /* zero the carry */ u = 0; for (i = 0; i < min; i++) { /* Compute the sum at one digit, T[i] = A[i] + B[i] + U */ *tmpc = *tmpa++ + *tmpb++ + u; /* U = carry bit of T[i] */ u = *tmpc >> ((mp_digit)DIGIT_BIT); /* take away carry bit from T[i] */ *tmpc++ &= MP_MASK; } /* now copy higher words if any, that is in A+B * if A or B has more digits add those in */ if (min != max) { for (; i < max; i++) { /* T[i] = X[i] + U */ *tmpc = x->dp[i] + u; /* U = carry bit of T[i] */ u = *tmpc >> ((mp_digit)DIGIT_BIT); /* take away carry bit from T[i] */ *tmpc++ &= MP_MASK; } } /* add carry */ *tmpc++ = u; /* clear digits above oldused */ for (i = c->used; i < olduse; i++) { *tmpc++ = 0; } } mp_clamp (c); return MP_OKAY; } int s_mp_exptmod (mp_int * G, mp_int * X, mp_int * P, mp_int * Y) { mp_int M[256], res, mu; mp_digit buf; int err, bitbuf, bitcpy, bitcnt, mode, digidx, x, y, winsize; /* find window size */ x = mp_count_bits (X); if (x <= 7) { winsize = 2; } else if (x <= 36) { winsize = 3; } else if (x <= 140) { winsize = 4; } else if (x <= 450) { winsize = 5; } else if (x <= 1303) { winsize = 6; } else if (x <= 3529) { winsize = 7; } else { winsize = 8; } /* init M array */ /* init first cell */ if ((err = mp_init(&M[1])) != MP_OKAY) { return err; } /* now init the second half of the array */ for (x = 1<<(winsize-1); x < (1 << winsize); x++) { if ((err = mp_init(&M[x])) != MP_OKAY) { for (y = 1<<(winsize-1); y < x; y++) { mp_clear (&M[y]); } mp_clear(&M[1]); return err; } } /* create mu, used for Barrett reduction */ if ((err = mp_init (&mu)) != MP_OKAY) { goto __M; } if ((err = mp_reduce_setup (&mu, P)) != MP_OKAY) { goto __MU; } /* create M table * * The M table contains powers of the base, * e.g. M[x] = G**x mod P * * The first half of the table is not * computed though accept for M[0] and M[1] */ if ((err = mp_mod (G, P, &M[1])) != MP_OKAY) { goto __MU; } /* compute the value at M[1<<(winsize-1)] by squaring * M[1] (winsize-1) times */ if ((err = mp_copy (&M[1], &M[1 << (winsize - 1)])) != MP_OKAY) { goto __MU; } for (x = 0; x < (winsize - 1); x++) { if ((err = mp_sqr (&M[1 << (winsize - 1)], &M[1 << (winsize - 1)])) != MP_OKAY) { goto __MU; } if ((err = mp_reduce (&M[1 << (winsize - 1)], P, &mu)) != MP_OKAY) { goto __MU; } } /* create upper table, that is M[x] = M[x-1] * M[1] (mod P) * for x = (2**(winsize - 1) + 1) to (2**winsize - 1) */ for (x = (1 << (winsize - 1)) + 1; x < (1 << winsize); x++) { if ((err = mp_mul (&M[x - 1], &M[1], &M[x])) != MP_OKAY) { goto __MU; } if ((err = mp_reduce (&M[x], P, &mu)) != MP_OKAY) { goto __MU; } } /* setup result */ if ((err = mp_init (&res)) != MP_OKAY) { goto __MU; } mp_set (&res, 1); /* set initial mode and bit cnt */ mode = 0; bitcnt = 1; buf = 0; digidx = X->used - 1; bitcpy = 0; bitbuf = 0; for (;;) { /* grab next digit as required */ if (--bitcnt == 0) { /* if digidx == -1 we are out of digits */ if (digidx == -1) { break; } /* read next digit and reset the bitcnt */ buf = X->dp[digidx--]; bitcnt = (int) DIGIT_BIT; } /* grab the next msb from the exponent */ y = (buf >> (mp_digit)(DIGIT_BIT - 1)) & 1; buf <<= (mp_digit)1; /* if the bit is zero and mode == 0 then we ignore it * These represent the leading zero bits before the first 1 bit * in the exponent. Technically this opt is not required but it * does lower the # of trivial squaring/reductions used */ if (mode == 0 && y == 0) { continue; } /* if the bit is zero and mode == 1 then we square */ if (mode == 1 && y == 0) { if ((err = mp_sqr (&res, &res)) != MP_OKAY) { goto __RES; } if ((err = mp_reduce (&res, P, &mu)) != MP_OKAY) { goto __RES; } continue; } /* else we add it to the window */ bitbuf |= (y << (winsize - ++bitcpy)); mode = 2; if (bitcpy == winsize) { /* ok window is filled so square as required and multiply */ /* square first */ for (x = 0; x < winsize; x++) { if ((err = mp_sqr (&res, &res)) != MP_OKAY) { goto __RES; } if ((err = mp_reduce (&res, P, &mu)) != MP_OKAY) { goto __RES; } } /* then multiply */ if ((err = mp_mul (&res, &M[bitbuf], &res)) != MP_OKAY) { goto __RES; } if ((err = mp_reduce (&res, P, &mu)) != MP_OKAY) { goto __RES; } /* empty window and reset */ bitcpy = 0; bitbuf = 0; mode = 1; } } /* if bits remain then square/multiply */ if (mode == 2 && bitcpy > 0) { /* square then multiply if the bit is set */ for (x = 0; x < bitcpy; x++) { if ((err = mp_sqr (&res, &res)) != MP_OKAY) { goto __RES; } if ((err = mp_reduce (&res, P, &mu)) != MP_OKAY) { goto __RES; } bitbuf <<= 1; if ((bitbuf & (1 << winsize)) != 0) { /* then multiply */ if ((err = mp_mul (&res, &M[1], &res)) != MP_OKAY) { goto __RES; } if ((err = mp_reduce (&res, P, &mu)) != MP_OKAY) { goto __RES; } } } } mp_exch (&res, Y); err = MP_OKAY; __RES:mp_clear (&res); __MU:mp_clear (&mu); __M: mp_clear(&M[1]); for (x = 1<<(winsize-1); x < (1 << winsize); x++) { mp_clear (&M[x]); } return err; } /* multiplies |a| * |b| and only computes up to digs digits of result * HAC pp. 595, Algorithm 14.12 Modified so you can control how * many digits of output are created. */ int s_mp_mul_digs (mp_int * a, mp_int * b, mp_int * c, int digs) { mp_int t; int res, pa, pb, ix, iy; mp_digit u; mp_word r; mp_digit tmpx, *tmpt, *tmpy; /* can we use the fast multiplier? */ if (((digs) < MP_WARRAY) && MIN (a->used, b->used) < (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) { return fast_s_mp_mul_digs (a, b, c, digs); } if ((res = mp_init_size (&t, digs)) != MP_OKAY) { return res; } t.used = digs; /* compute the digits of the product directly */ pa = a->used; for (ix = 0; ix < pa; ix++) { /* set the carry to zero */ u = 0; /* limit ourselves to making digs digits of output */ pb = MIN (b->used, digs - ix); /* setup some aliases */ /* copy of the digit from a used within the nested loop */ tmpx = a->dp[ix]; /* an alias for the destination shifted ix places */ tmpt = t.dp + ix; /* an alias for the digits of b */ tmpy = b->dp; /* compute the columns of the output and propagate the carry */ for (iy = 0; iy < pb; iy++) { /* compute the column as a mp_word */ r = ((mp_word)*tmpt) + ((mp_word)tmpx) * ((mp_word)*tmpy++) + ((mp_word) u); /* the new column is the lower part of the result */ *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK)); /* get the carry word from the result */ u = (mp_digit) (r >> ((mp_word) DIGIT_BIT)); } /* set carry if it is placed below digs */ if (ix + iy < digs) { *tmpt = u; } } mp_clamp (&t); mp_exch (&t, c); mp_clear (&t); return MP_OKAY; } /* multiplies |a| * |b| and does not compute the lower digs digits * [meant to get the higher part of the product] */ int s_mp_mul_high_digs (mp_int * a, mp_int * b, mp_int * c, int digs) { mp_int t; int res, pa, pb, ix, iy; mp_digit u; mp_word r; mp_digit tmpx, *tmpt, *tmpy; /* can we use the fast multiplier? */ if (((a->used + b->used + 1) < MP_WARRAY) && MIN (a->used, b->used) < (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) { return fast_s_mp_mul_high_digs (a, b, c, digs); } if ((res = mp_init_size (&t, a->used + b->used + 1)) != MP_OKAY) { return res; } t.used = a->used + b->used + 1; pa = a->used; pb = b->used; for (ix = 0; ix < pa; ix++) { /* clear the carry */ u = 0; /* left hand side of A[ix] * B[iy] */ tmpx = a->dp[ix]; /* alias to the address of where the digits will be stored */ tmpt = &(t.dp[digs]); /* alias for where to read the right hand side from */ tmpy = b->dp + (digs - ix); for (iy = digs - ix; iy < pb; iy++) { /* calculate the double precision result */ r = ((mp_word)*tmpt) + ((mp_word)tmpx) * ((mp_word)*tmpy++) + ((mp_word) u); /* get the lower part */ *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK)); /* carry the carry */ u = (mp_digit) (r >> ((mp_word) DIGIT_BIT)); } *tmpt = u; } mp_clamp (&t); mp_exch (&t, c); mp_clear (&t); return MP_OKAY; } /* low level squaring, b = a*a, HAC pp.596-597, Algorithm 14.16 */ int s_mp_sqr (mp_int * a, mp_int * b) { mp_int t; int res, ix, iy, pa; mp_word r; mp_digit u, tmpx, *tmpt; pa = a->used; if ((res = mp_init_size (&t, 2*pa + 1)) != MP_OKAY) { return res; } /* default used is maximum possible size */ t.used = 2*pa + 1; for (ix = 0; ix < pa; ix++) { /* first calculate the digit at 2*ix */ /* calculate double precision result */ r = ((mp_word) t.dp[2*ix]) + ((mp_word)a->dp[ix])*((mp_word)a->dp[ix]); /* store lower part in result */ t.dp[ix+ix] = (mp_digit) (r & ((mp_word) MP_MASK)); /* get the carry */ u = (mp_digit)(r >> ((mp_word) DIGIT_BIT)); /* left hand side of A[ix] * A[iy] */ tmpx = a->dp[ix]; /* alias for where to store the results */ tmpt = t.dp + (2*ix + 1); for (iy = ix + 1; iy < pa; iy++) { /* first calculate the product */ r = ((mp_word)tmpx) * ((mp_word)a->dp[iy]); /* now calculate the double precision result, note we use * addition instead of *2 since it's easier to optimize */ r = ((mp_word) *tmpt) + r + r + ((mp_word) u); /* store lower part */ *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK)); /* get carry */ u = (mp_digit)(r >> ((mp_word) DIGIT_BIT)); } /* propagate upwards */ while (u != ((mp_digit) 0)) { r = ((mp_word) *tmpt) + ((mp_word) u); *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK)); u = (mp_digit)(r >> ((mp_word) DIGIT_BIT)); } } mp_clamp (&t); mp_exch (&t, b); mp_clear (&t); return MP_OKAY; } /* low level subtraction (assumes |a| > |b|), HAC pp.595 Algorithm 14.9 */ int s_mp_sub (mp_int * a, mp_int * b, mp_int * c) { int olduse, res, min, max; /* find sizes */ min = b->used; max = a->used; /* init result */ if (c->alloc < max) { if ((res = mp_grow (c, max)) != MP_OKAY) { return res; } } olduse = c->used; c->used = max; { register mp_digit u, *tmpa, *tmpb, *tmpc; register int i; /* alias for digit pointers */ tmpa = a->dp; tmpb = b->dp; tmpc = c->dp; /* set carry to zero */ u = 0; for (i = 0; i < min; i++) { /* T[i] = A[i] - B[i] - U */ *tmpc = *tmpa++ - *tmpb++ - u; /* U = carry bit of T[i] * Note this saves performing an AND operation since * if a carry does occur it will propagate all the way to the * MSB. As a result a single shift is enough to get the carry */ u = *tmpc >> ((mp_digit)(CHAR_BIT * sizeof (mp_digit) - 1)); /* Clear carry from T[i] */ *tmpc++ &= MP_MASK; } /* now copy higher words if any, e.g. if A has more digits than B */ for (; i < max; i++) { /* T[i] = A[i] - U */ *tmpc = *tmpa++ - u; /* U = carry bit of T[i] */ u = *tmpc >> ((mp_digit)(CHAR_BIT * sizeof (mp_digit) - 1)); /* Clear carry from T[i] */ *tmpc++ &= MP_MASK; } /* clear digits above used (since we may not have grown result above) */ for (i = c->used; i < olduse; i++) { *tmpc++ = 0; } } mp_clamp (c); return MP_OKAY; } /* Known optimal configurations CPU /Compiler /MUL CUTOFF/SQR CUTOFF ------------------------------------------------------------- Intel P4 Northwood /GCC v3.4.1 / 88/ 128/LTM 0.32 ;-) */ int KARATSUBA_MUL_CUTOFF = 88, /* Min. number of digits before Karatsuba multiplication is used. */ KARATSUBA_SQR_CUTOFF = 128; /* Min. number of digits before Karatsuba squaring is used. */