X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=crypto%2Fec%2Fec2_mult.c;h=06405d0716fff0c4d5c82af2b4f6967f0d87badf;hb=f063e30fe9f316067950bdf0397b51cf87d4b6a6;hp=ff368fd7d7b3d277db18ab1884aa59201d80692a;hpb=aa4ce7315f65fdf8940d5bc9e562aa478f0335d3;p=oweals%2Fopenssl.git diff --git a/crypto/ec/ec2_mult.c b/crypto/ec/ec2_mult.c index ff368fd7d7..06405d0716 100644 --- a/crypto/ec/ec2_mult.c +++ b/crypto/ec/ec2_mult.c @@ -67,16 +67,20 @@ * */ +#define OPENSSL_FIPSAPI + #include #include "ec_lcl.h" +#ifndef OPENSSL_NO_EC2M + /* Compute the x-coordinate x/z for the point 2*(x/z) in Montgomery projective * coordinates. * Uses algorithm Mdouble in appendix of * Lopez, J. and Dahab, R. "Fast multiplication on elliptic curves over - * GF(2^m) without precomputation". + * GF(2^m) without precomputation" (CHES '99, LNCS 1717). * modified to not require precomputation of c=b^{2^{m-1}}. */ static int gf2m_Mdouble(const EC_GROUP *group, BIGNUM *x, BIGNUM *z, BN_CTX *ctx) @@ -107,8 +111,8 @@ static int gf2m_Mdouble(const EC_GROUP *group, BIGNUM *x, BIGNUM *z, BN_CTX *ctx /* Compute the x-coordinate x1/z1 for the point (x1/z1)+(x2/x2) in Montgomery * projective coordinates. * Uses algorithm Madd in appendix of - * Lopex, J. and Dahab, R. "Fast multiplication on elliptic curves over - * GF(2^m) without precomputation". + * Lopez, J. and Dahab, R. "Fast multiplication on elliptic curves over + * GF(2^m) without precomputation" (CHES '99, LNCS 1717). */ static int gf2m_Madd(const EC_GROUP *group, const BIGNUM *x, BIGNUM *x1, BIGNUM *z1, const BIGNUM *x2, const BIGNUM *z2, BN_CTX *ctx) @@ -140,8 +144,8 @@ static int gf2m_Madd(const EC_GROUP *group, const BIGNUM *x, BIGNUM *x1, BIGNUM /* Compute the x, y affine coordinates from the point (x1, z1) (x2, z2) * using Montgomery point multiplication algorithm Mxy() in appendix of - * Lopex, J. and Dahab, R. "Fast multiplication on elliptic curves over - * GF(2^m) without precomputation". + * Lopez, J. and Dahab, R. "Fast multiplication on elliptic curves over + * GF(2^m) without precomputation" (CHES '99, LNCS 1717). * Returns: * 0 on error * 1 if return value should be the point at infinity @@ -206,18 +210,22 @@ static int gf2m_Mxy(const EC_GROUP *group, const BIGNUM *x, const BIGNUM *y, BIG return ret; } + /* Computes scalar*point and stores the result in r. * point can not equal r. - * Uses algorithm 2P of - * Lopex, J. and Dahab, R. "Fast multiplication on elliptic curves over - * GF(2^m) without precomputation". + * Uses a modified algorithm 2P of + * Lopez, J. and Dahab, R. "Fast multiplication on elliptic curves over + * GF(2^m) without precomputation" (CHES '99, LNCS 1717). + * + * To protect against side-channel attack the function uses constant time swap, + * avoiding conditional branches. */ static int ec_GF2m_montgomery_point_multiply(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar, const EC_POINT *point, BN_CTX *ctx) { BIGNUM *x1, *x2, *z1, *z2; - int ret = 0, i, j; - BN_ULONG mask; + int ret = 0, i; + BN_ULONG mask,word; if (r == point) { @@ -244,6 +252,11 @@ static int ec_GF2m_montgomery_point_multiply(const EC_GROUP *group, EC_POINT *r, x2 = &r->X; z2 = &r->Y; + bn_wexpand(x1, group->field.top); + bn_wexpand(z1, group->field.top); + bn_wexpand(x2, group->field.top); + bn_wexpand(z2, group->field.top); + if (!BN_GF2m_mod_arr(x1, &point->X, group->poly)) goto err; /* x1 = x */ if (!BN_one(z1)) goto err; /* z1 = 1 */ if (!group->meth->field_sqr(group, z2, x1, ctx)) goto err; /* z2 = x1^2 = x^2 */ @@ -251,34 +264,31 @@ static int ec_GF2m_montgomery_point_multiply(const EC_GROUP *group, EC_POINT *r, if (!BN_GF2m_add(x2, x2, &group->b)) goto err; /* x2 = x^4 + b */ /* find top most bit and go one past it */ - i = scalar->top - 1; j = BN_BITS2 - 1; + i = scalar->top - 1; mask = BN_TBIT; - while (!(scalar->d[i] & mask)) { mask >>= 1; j--; } - mask >>= 1; j--; + word = scalar->d[i]; + while (!(word & mask)) mask >>= 1; + mask >>= 1; /* if top most bit was at word break, go to next word */ if (!mask) { - i--; j = BN_BITS2 - 1; + i--; mask = BN_TBIT; } for (; i >= 0; i--) { - for (; j >= 0; j--) + word = scalar->d[i]; + while (mask) { - if (scalar->d[i] & mask) - { - if (!gf2m_Madd(group, &point->X, x1, z1, x2, z2, ctx)) goto err; - if (!gf2m_Mdouble(group, x2, z2, ctx)) goto err; - } - else - { - if (!gf2m_Madd(group, &point->X, x2, z2, x1, z1, ctx)) goto err; - if (!gf2m_Mdouble(group, x1, z1, ctx)) goto err; - } + BN_consttime_swap(word & mask, x1, x2, group->field.top); + BN_consttime_swap(word & mask, z1, z2, group->field.top); + if (!gf2m_Madd(group, &point->X, x2, z2, x1, z1, ctx)) goto err; + if (!gf2m_Mdouble(group, x1, z1, ctx)) goto err; + BN_consttime_swap(word & mask, x1, x2, group->field.top); + BN_consttime_swap(word & mask, z1, z2, group->field.top); mask >>= 1; } - j = BN_BITS2 - 1; mask = BN_TBIT; } @@ -318,6 +328,7 @@ int ec_GF2m_simple_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar, int ret = 0; size_t i; EC_POINT *p=NULL; + EC_POINT *acc = NULL; if (ctx == NULL) { @@ -337,15 +348,16 @@ int ec_GF2m_simple_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar, } if ((p = EC_POINT_new(group)) == NULL) goto err; + if ((acc = EC_POINT_new(group)) == NULL) goto err; - if (!EC_POINT_set_to_infinity(group, r)) goto err; + if (!EC_POINT_set_to_infinity(group, acc)) goto err; if (scalar) { if (!ec_GF2m_montgomery_point_multiply(group, p, scalar, group->generator, ctx)) goto err; - if (BN_is_negative(scalar)) + if (BN_is_negative(scalar)) if (!group->meth->invert(group, p, ctx)) goto err; - if (!group->meth->add(group, r, r, p, ctx)) goto err; + if (!group->meth->add(group, acc, acc, p, ctx)) goto err; } for (i = 0; i < num; i++) @@ -353,13 +365,16 @@ int ec_GF2m_simple_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar, if (!ec_GF2m_montgomery_point_multiply(group, p, scalars[i], points[i], ctx)) goto err; if (BN_is_negative(scalars[i])) if (!group->meth->invert(group, p, ctx)) goto err; - if (!group->meth->add(group, r, r, p, ctx)) goto err; + if (!group->meth->add(group, acc, acc, p, ctx)) goto err; } + if (!EC_POINT_copy(r, acc)) goto err; + ret = 1; err: if (p) EC_POINT_free(p); + if (acc) EC_POINT_free(acc); if (new_ctx != NULL) BN_CTX_free(new_ctx); return ret; @@ -378,3 +393,5 @@ int ec_GF2m_have_precompute_mult(const EC_GROUP *group) { return ec_wNAF_have_precompute_mult(group); } + +#endif