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fix ed25519-donna signature malleability

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This commit is contained in:
Ondřej Vejpustek 2018-07-16 12:37:47 +02:00 committed by Pavol Rusnak
parent 9b2de9584d
commit 8318ac35fc
3 changed files with 17 additions and 1 deletions
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4
ed25519-donna/ed25519.c
View File

@ -189,7 +189,9 @@ ED25519_FN(ed25519_sign_open) (const unsigned char *m, size_t mlen, const ed2551
expand256_modm(hram, hash, 64);
/* S */
expand256_modm(S, RS + 32, 32);
expand_raw256_modm(S, RS + 32);
if (!is_reduced256_modm(S))
return -1;
/* SB - H(R,A,m)A */
ge25519_double_scalarmult_vartime(&R, &A, hram, S);

12
ed25519-donna/modm-donna-32bit.c
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@ -310,6 +310,18 @@ void expand_raw256_modm(bignum256modm out, const unsigned char in[32]) {
out[8] = ((x[ 7] >> 16) ) & 0x0000ffff;
}
int is_reduced256_modm(const bignum256modm in)
{
int i;
uint32_t res1 = 0;
uint32_t res2 = 0;
for (i = 8; i >= 0; i--) {
res1 = (res1 << 1) | (in[i] < modm_m[i]);
res2 = (res2 << 1) | (in[i] > modm_m[i]);
}
return res1 > res2;
}
void contract256_modm(unsigned char out[32], const bignum256modm in) {
U32TO8_LE(out + 0, (in[0] ) | (in[1] << 30));
U32TO8_LE(out + 4, (in[1] >> 2) | (in[2] << 28));

2
ed25519-donna/modm-donna-32bit.h
View File

@ -44,6 +44,8 @@ void expand256_modm(bignum256modm out, const unsigned char *in, size_t len);
void expand_raw256_modm(bignum256modm out, const unsigned char in[32]);
int is_reduced256_modm(const bignum256modm in);
void contract256_modm(unsigned char out[32], const bignum256modm in);
void contract256_window4_modm(signed char r[64], const bignum256modm in);