diff options
| -rw-r--r-- | include/libuecc/ecc.h | 11 | ||||
| -rw-r--r-- | src/ec25519.c | 38 | ||||
| -rw-r--r-- | src/ec25519_secret.c | 28 |
3 files changed, 53 insertions, 24 deletions
diff --git a/include/libuecc/ecc.h b/include/libuecc/ecc.h index 9cf2b1e..f535702 100644 --- a/include/libuecc/ecc.h +++ b/include/libuecc/ecc.h @@ -45,13 +45,16 @@ typedef struct _ecc_25519_work { void ecc_25519_load(ecc_25519_work *out, const ecc_public_key_256 *in); void ecc_25519_store(ecc_public_key_256 *out, const ecc_25519_work *in); -void ecc_25519_add_secret(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2); -void ecc_25519_sub_secret(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2); -void ecc_25519_mult_secret(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2); - +int ecc_25519_is_infinity(const ecc_25519_work *in); void ecc_25519_add(ecc_25519_work *out, const ecc_25519_work *in1, const ecc_25519_work *in2); void ecc_25519_double(ecc_25519_work *out, const ecc_25519_work *in); void ecc_25519_scalarmult(ecc_25519_work *out, const ecc_secret_key_256 *n, const ecc_25519_work *base); void ecc_25519_scalarmult_base(ecc_25519_work *out, const ecc_secret_key_256 *n); +int ecc_25519_secret_is_zero(const ecc_secret_key_256 *in); +void ecc_25519_secret_add(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2); +void ecc_25519_secret_sub(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2); +void ecc_25519_secret_reduce(ecc_secret_key_256 *out, const ecc_secret_key_256 *in); +void ecc_25519_secret_mult(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2); + #endif /* _LIBUECC_ECC_H_ */ diff --git a/src/ec25519.c b/src/ec25519.c index 889264d..b9ca4e9 100644 --- a/src/ec25519.c +++ b/src/ec25519.c @@ -135,18 +135,6 @@ static void square(unsigned int out[32], const unsigned int a[32]) { squeeze(out); } -static int check_zero(const unsigned int x[32]) { - unsigned int differentbits = 0; - int i; - - for (i = 0; i < 32; i++) { - differentbits |= (x[i] & 0xffff); - differentbits |= (x[i] >> 16); - } - - return (1-(1 & ((differentbits - 1) >> 16))); -} - static int check_equal(const unsigned int x[32], const unsigned int y[32]) { unsigned int differentbits = 0; int i; @@ -156,7 +144,19 @@ static int check_equal(const unsigned int x[32], const unsigned int y[32]) { differentbits |= ((x[i] ^ y[i]) >> 16); } - return (1-(1 & ((differentbits - 1) >> 16))); + return (1 & ((differentbits - 1) >> 16)); +} + +static int check_zero(const unsigned int x[32]) { + static const unsigned int zero[32] = {0}; + static const unsigned int p[32] = { + 0xed, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f + }; + + return (check_equal(x, zero) | check_equal(x, p)); } static void selectw(ecc_25519_work *out, const ecc_25519_work *r, const ecc_25519_work *s, unsigned int b) { @@ -275,7 +275,7 @@ static void square_root(unsigned int out[32], const unsigned int z[32]) { mult(z2_252_1_rho_s, z2_252_1, rho_s); - select(out, z2_252_1_rho_s, z2_252_1, check_equal(t1, minus1)); + select(out, z2_252_1, z2_252_1_rho_s, check_equal(t1, minus1)); } static void recip(unsigned int out[32], const unsigned int z[32]) { @@ -389,6 +389,10 @@ void ecc_25519_store(ecc_public_key_256 *out, const ecc_25519_work *in) { static const ecc_25519_work infty = {{0}, {0}, {1}}; +int ecc_25519_is_infinity(const ecc_25519_work *in) { + return (check_zero(in->X)|check_zero(in->Y)); +} + void ecc_25519_double(ecc_25519_work *out, const ecc_25519_work *in) { unsigned int A[32], B[32], C[32], D[32], E[32], U[32], t0[32], t1[32], t2[32], t3[32], t4[32], t5[32]; @@ -407,7 +411,7 @@ void ecc_25519_double(ecc_25519_work *out, const ecc_25519_work *in) { sub(t5, C, t4); mult(out->Y, E, t5); mult(out->Z, D, E); - selectw(out, &infty, out, check_zero(out->X)*check_zero(out->Y)); + selectw(out, out, &infty, ecc_25519_is_infinity(out)); } void ecc_25519_add(ecc_25519_work *out, const ecc_25519_work *in1, const ecc_25519_work *in2) { @@ -432,8 +436,8 @@ void ecc_25519_add(ecc_25519_work *out, const ecc_25519_work *in1, const ecc_255 mult(out->Y, t7, I); mult(t8, H, I); mult(out->Z, A, t8); - selectw(out, in1, out, check_zero(t3)); - selectw(out, in2, out, check_zero(t2)); + selectw(out, out, in1, check_zero(t3)); + selectw(out, out, in2, check_zero(t2)); } void ecc_25519_scalarmult(ecc_25519_work *out, const ecc_secret_key_256 *n, const ecc_25519_work *base) { diff --git a/src/ec25519_secret.c b/src/ec25519_secret.c index 0a58629..b79b46c 100644 --- a/src/ec25519_secret.c +++ b/src/ec25519_secret.c @@ -56,7 +56,20 @@ static void select(unsigned char out[32], const unsigned char r[32], const unsig } } -void ecc_25519_add_secret(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) { +int ecc_25519_secret_is_zero(const ecc_secret_key_256 *in) { + int i; + ecc_secret_key_256 r; + unsigned int bits; + + ecc_25519_secret_reduce(&r, in); + + for (i = 0; i < 32; i++) + bits |= r.s[i]; + + return (((bits-1)>>8) & 1); +} + +void ecc_25519_secret_add(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) { unsigned int j; int u1, u2, u3; unsigned char out1[32], out2[32], out3[32]; @@ -81,7 +94,7 @@ void ecc_25519_add_secret(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1 select(out->s, out->s, out3, ((u1 >> 8) & (u2 >> 8)) & 1); } -void ecc_25519_sub_secret(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) { +void ecc_25519_secret_sub(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) { unsigned int j; int u1, u2, u3; unsigned char out1[32], out2[32], out3[32]; @@ -128,6 +141,15 @@ static void reduce(unsigned char a[32]) { select(a, out1, out2, IS_NEGATIVE(u1)); } +void ecc_25519_secret_reduce(ecc_secret_key_256 *out, const ecc_secret_key_256 *in) { + int i; + + for (i = 0; i < 32; i++) + out->s[i] = in->s[i]; + + reduce(out->s); +} + /* Montgomery modular multiplication algorithm */ static void montgomery(unsigned char out[32], const unsigned char a[32], const unsigned char b[32]) { unsigned int a_i; @@ -157,7 +179,7 @@ static void montgomery(unsigned char out[32], const unsigned char a[32], const u } -void ecc_25519_mult_secret(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) { +void ecc_25519_secret_mult(ecc_secret_key_256 *out, const ecc_secret_key_256 *in1, const ecc_secret_key_256 *in2) { /* 2^512 mod p */ static const unsigned char C[32] = { 0x01, 0x0f, 0x9c, 0x44, 0xe3, 0x11, 0x06, 0xa4, |