int
crypto_sign_verify_detached(const unsigned char *sig, const unsigned char *m,
unsigned long long mlen, const unsigned char *pk)
{
crypto_hash_sha512_state hs;
unsigned char h[64];
unsigned char rcheck[32];
unsigned int i;
unsigned char d = 0;
ge_p3 A;
ge_p2 R;
#ifdef ED25519_PREVENT_MALLEABILITY
if (crypto_sign_check_S_lt_l(sig + 32) != 0) {
return -1;
}
#else
if (sig[63] & 224) {
return -1;
}
#endif
if (ge_frombytes_negate_vartime(&A, pk) != 0) {
return -1;
}
for (i = 0; i < 32; ++i) {
d |= pk[i];
}
if (d == 0) {
return -1;
}
crypto_hash_sha512_init(&hs);
crypto_hash_sha512_update(&hs, sig, 32);
crypto_hash_sha512_update(&hs, pk, 32);
crypto_hash_sha512_update(&hs, m, mlen);
crypto_hash_sha512_final(&hs, h);
sc_reduce(h);
ge_double_scalarmult_vartime(&R, h, &A, sig + 32);
ge_tobytes(rcheck, &R);
return crypto_verify_32(rcheck, sig) | (-(rcheck - sig == 0)) |
sodium_memcmp(sig, rcheck, 32);
}
bool RippleAddress::signatureIsCanonical(Blob const& vchSig)
{
return crypto_sign_check_S_lt_l(
((const unsigned char*) vchSig.data ()) + 32
) == 0;
}
