diff options
Diffstat (limited to 'crypto/ec/ec2_mult.c')
| -rw-r--r-- | crypto/ec/ec2_mult.c | 37 |
1 files changed, 21 insertions, 16 deletions
diff --git a/crypto/ec/ec2_mult.c b/crypto/ec/ec2_mult.c index 7dca5e4bcd436..26f4a783fcc1e 100644 --- a/crypto/ec/ec2_mult.c +++ b/crypto/ec/ec2_mult.c @@ -71,12 +71,14 @@ #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 +109,8 @@ 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 +142,8 @@ 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 @@ -209,15 +211,15 @@ static int gf2m_Mxy(const EC_GROUP *group, const BIGNUM *x, const BIGNUM *y, BIG /* 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". + * Lopez, J. and Dahab, R. "Fast multiplication on elliptic curves over + * GF(2^m) without precomputation" (CHES '99, LNCS 1717). */ 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) { @@ -251,22 +253,24 @@ 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 (word & mask) { if (!gf2m_Madd(group, &point->X, x1, z1, x2, z2, ctx)) goto err; if (!gf2m_Mdouble(group, x2, z2, ctx)) goto err; @@ -278,7 +282,6 @@ static int ec_GF2m_montgomery_point_multiply(const EC_GROUP *group, EC_POINT *r, } mask >>= 1; } - j = BN_BITS2 - 1; mask = BN_TBIT; } @@ -383,3 +386,5 @@ int ec_GF2m_have_precompute_mult(const EC_GROUP *group) { return ec_wNAF_have_precompute_mult(group); } + +#endif |