int crypto_sign_open(
unsigned char *m,unsigned long long *mlen,
const unsigned char *sm,unsigned long long smlen,
const unsigned char *pk
)
{
unsigned char pkcopy[32];
unsigned char rcopy[32];
unsigned char hram[64];
unsigned char rcheck[32];
ge25519 get1, get2;
sc25519 schram, scs;
if (smlen < 64) goto badsig;
if (sm[63] & 224) goto badsig;
if (ge25519_unpackneg_vartime(&get1,pk)) goto badsig;
memmove(pkcopy,pk,32);
memmove(rcopy,sm,32);
sc25519_from32bytes(&scs, sm+32);
memmove(m,sm,smlen);
memmove(m + 32,pkcopy,32);
crypto_hash_sha512(hram,m,smlen);
sc25519_from64bytes(&schram, hram);
ge25519_double_scalarmult_vartime(&get2, &get1, &schram, &ge25519_base, &scs);
ge25519_pack(rcheck, &get2);
if (crypto_verify_32(rcopy,rcheck) == 0) {
memmove(m,m + 64,smlen - 64);
memset(m + smlen - 64,0,64);
*mlen = smlen - 64;
return 0;
}
badsig:
*mlen = (unsigned long long) -1;
memset(m,0,smlen);
return -1;
}
int crypto_sign_ed25519_open(
unsigned char *m,unsigned long long *mlen,
const unsigned char *sm,unsigned long long smlen,
const unsigned char *pk
)
{
unsigned int i;
int ret;
unsigned char t2[32];
ge25519 get1, get2;
sc25519 schram, scs;
unsigned char hram[crypto_hash_sha512_BYTES];
*mlen = (unsigned long long) -1;
if (smlen < 64) return -1;
if (ge25519_unpackneg_vartime(&get1, pk)) return -1;
get_hram(hram,sm,pk,m,smlen);
sc25519_from64bytes(&schram, hram);
sc25519_from32bytes(&scs, sm+32);
ge25519_double_scalarmult_vartime(&get2, &get1, &schram, &ge25519_base, &scs);
ge25519_pack(t2, &get2);
ret = crypto_verify_32(sm, t2);
if (!ret)
{
for(i=0;i<smlen-64;i++)
m[i] = sm[i + 64];
*mlen = smlen-64;
}
else
{
for(i=0;i<smlen-64;i++)
m[i] = 0;
}
return ret;
}
// Step 3 bis
// verify pk_r = y.B - c.pk with pk = sk.B
int schnorr_id_verify(const uint8_t pk[SCHNORR_PUBLICKEYBYTES],
const uint8_t pk_r[SCHNORR_PUBLICKEYBYTES],
const uint8_t challenge[SCHNORR_ID_CHALLENGEBYTES],
const uint8_t response[SCHNORR_ID_RESPONSEBYTES]) {
ge25519 ge_pk_neg;
sc25519 sc_challenge;
sc25519 sc_response;
ge25519 ge_pk_r_verifier;
uint8_t pk_r_verifier[SCHNORR_PUBLICKEYBYTES];
if (ge25519_unpackneg_vartime(&ge_pk_neg, pk))
return -1;
sc25519_from_challenge_bytes(&sc_challenge, challenge);
sc25519_from32bytes(&sc_response, response);
ge25519_double_scalarmult_vartime(&ge_pk_r_verifier,
&ge_pk_neg, &sc_challenge,
&ge25519_base, &sc_response);
ge25519_pack(pk_r_verifier, &ge_pk_r_verifier);
return verify_32(pk_r, pk_r_verifier);
}
int crypto_sign_open_batch(
unsigned char* const m[],unsigned long long mlen[],
unsigned char* const sm[],const unsigned long long smlen[],
unsigned char* const pk[],
unsigned long long num
)
{
int ret = 0;
unsigned long long i, j;
shortsc25519 r[MAXBATCH];
sc25519 scalars[2*MAXBATCH+1];
ge25519 points[2*MAXBATCH+1];
unsigned char hram[crypto_hash_sha512_BYTES];
unsigned long long batchsize;
for (i = 0;i < num;++i) mlen[i] = -1;
while (num >= 3) {
batchsize = num;
if (batchsize > MAXBATCH) batchsize = MAXBATCH;
for (i = 0;i < batchsize;++i)
if (smlen[i] < 64) goto fallback;
randombytes((unsigned char*)r,sizeof(shortsc25519) * batchsize);
/* Computing scalars[0] = ((r1s1 + r2s2 + ...)) */
for(i=0;i<batchsize;i++)
{
sc25519_from32bytes(&scalars[i], sm[i]+32);
sc25519_mul_shortsc(&scalars[i], &scalars[i], &r[i]);
}
for(i=1;i<batchsize;i++)
sc25519_add(&scalars[0], &scalars[0], &scalars[i]);
/* Computing scalars[1] ... scalars[batchsize] as r[i]*H(R[i],A[i],m[i]) */
for(i=0;i<batchsize;i++)
{
get_hram(hram, sm[i], pk[i], m[i], smlen[i]);
sc25519_from64bytes(&scalars[i+1],hram);
sc25519_mul_shortsc(&scalars[i+1],&scalars[i+1],&r[i]);
}
/* Setting scalars[batchsize+1] ... scalars[2*batchsize] to r[i] */
for(i=0;i<batchsize;i++)
sc25519_from_shortsc(&scalars[batchsize+i+1],&r[i]);
/* Computing points */
points[0] = ge25519_base;
for(i=0;i<batchsize;i++)
if (ge25519_unpackneg_vartime(&points[i+1], pk[i])) goto fallback;
for(i=0;i<batchsize;i++)
if (ge25519_unpackneg_vartime(&points[batchsize+i+1], sm[i])) goto fallback;
ge25519_multi_scalarmult_vartime(points, points, scalars, 2*batchsize+1);
if (ge25519_isneutral_vartime(points)) {
for(i=0;i<batchsize;i++)
{
for(j=0;j<smlen[i]-64;j++)
m[i][j] = sm[i][j + 64];
mlen[i] = smlen[i]-64;
}
} else {
fallback:
for (i = 0;i < batchsize;++i)
ret |= crypto_sign_open(m[i], &mlen[i], sm[i], smlen[i], pk[i]);
}
m += batchsize;
mlen += batchsize;
sm += batchsize;
smlen += batchsize;
pk += batchsize;
num -= batchsize;
}
for (i = 0;i < num;++i)
ret |= crypto_sign_open(m[i], &mlen[i], sm[i], smlen[i], pk[i]);
return ret;
}