void
ED25519_FN(ed25519_sign) (const unsigned char *m, size_t mlen, const ed25519_secret_key sk, const ed25519_public_key pk, ed25519_signature RS) {
ed25519_hash_context ctx;
bignum256modm r, S, a;
ge25519 MM16 R;
hash_512bits extsk, hashr, hram;
ed25519_extsk(extsk, sk);
/* r = H(aExt[32..64], m) */
ed25519_hash_init(&ctx);
ed25519_hash_update(&ctx, extsk + 32, 32);
ed25519_hash_update(&ctx, m, mlen);
ed25519_hash_final(&ctx, hashr);
expand256_modm(r, hashr, 64);
/* R = rB */
ge25519_scalarmult_base_niels(&R, ge25519_niels_base_multiples, r);
ge25519_pack(RS, &R);
/* S = H(R,A,m).. */
ed25519_hram(hram, RS, pk, m, mlen);
expand256_modm(S, hram, 64);
/* S = H(R,A,m)a */
expand256_modm(a, extsk, 32);
mul256_modm(S, S, a);
/* S = (r + H(R,A,m)a) */
add256_modm(S, S, r);
/* S = (r + H(R,A,m)a) mod L */
contract256_modm(RS + 32, S);
}
void
ED25519_FN(curved25519_scalarmult_basepoint) (curved25519_key pk, const curved25519_key e) {
curved25519_key ec;
bignum256modm s;
bignum25519 MM16 yplusz, zminusy;
ge25519 MM16 p;
size_t i;
/* clamp */
for (i = 0; i < 32; i++) ec[i] = e[i];
ec[0] &= 248;
ec[31] &= 127;
ec[31] |= 64;
expand_raw256_modm(s, ec);
/* scalar * basepoint */
ge25519_scalarmult_base_niels(&p, ge25519_niels_base_multiples, s);
/* u = (y + z) / (z - y) */
curve25519_add(yplusz, p.y, p.z);
curve25519_sub(zminusy, p.z, p.y);
curve25519_recip(zminusy, zminusy);
curve25519_mul(yplusz, yplusz, zminusy);
curve25519_contract(pk, yplusz);
}
void
ed25519_sign(const unsigned char *m, size_t mlen, const ed25519_secret_key sk, const ed25519_public_key pk, ed25519_signature RS) {
SHA512_CTX shactx;
bignum256modm r, S, a;
ge25519 MM16 R;
hash_512bits extsk, hashr, hram;
ed25519_extsk(extsk, sk);
/* r = H(aExt[32..64], m) */
SHA512_Init(&shactx);
SHA512_Update(&shactx, extsk + 32, 32);
SHA512_Update(&shactx, m, mlen);
SHA512_Final(hashr, &shactx);
expand256_modm(r, hashr, 64);
/* R = rB */
ge25519_scalarmult_base_niels(&R, r);
ge25519_pack(RS, &R);
/* S = H(R,A,m).. */
ed25519_hram(hram, RS, pk, m, mlen);
expand256_modm(S, hram, 64);
/* S = H(R,A,m)a */
expand256_modm(a, extsk, 32);
mul256_modm(S, S, a);
/* S = (r + H(R,A,m)a) */
add256_modm(S, S, r);
/* S = (r + H(R,A,m)a) mod L */
contract256_modm(RS + 32, S);
}
void
ED25519_FN(ed25519_publickey) (const ed25519_secret_key sk, ed25519_public_key pk) {
bignum256modm a;
ge25519 MM16 A;
hash_512bits extsk;
/* A = aB */
ed25519_extsk(extsk, sk);
expand256_modm(a, extsk, 32);
ge25519_scalarmult_base_niels(&A, ge25519_niels_base_multiples, a);
ge25519_pack(pk, &A);
}
int
ed25519_donna_pubkey(unsigned char *pk, const unsigned char *sk)
{
bignum256modm a = {0};
ge25519 ALIGN(16) A = {{0}, {0}, {0}, {0}};
/* A = aB */
expand256_modm(a, sk, 32);
ge25519_scalarmult_base_niels(&A, ge25519_niels_base_multiples, a);
ge25519_pack(pk, &A);
return 0;
}
int
ed25519_donna_sign(unsigned char *sig, const unsigned char *m, size_t mlen,
const unsigned char *sk, const unsigned char *pk)
{
ed25519_hash_context ctx;
bignum256modm r = {0}, S, a;
ge25519 ALIGN(16) R = {{0}, {0}, {0}, {0}};
hash_512bits hashr, hram;
/* This is equivalent to the removed `ED25519_FN(ed25519_sign)` routine,
* except that the key expansion step is omitted as sk already is in expanded
* form.
*/
/* r = H(aExt[32..64], m) */
ed25519_hash_init(&ctx);
ed25519_hash_update(&ctx, sk + 32, 32);
ed25519_hash_update(&ctx, m, mlen);
ed25519_hash_final(&ctx, hashr);
expand256_modm(r, hashr, 64);
/* R = rB */
ge25519_scalarmult_base_niels(&R, ge25519_niels_base_multiples, r);
ge25519_pack(sig, &R);
/* S = H(R,A,m).. */
ed25519_hram(hram, sig, pk, m, mlen);
expand256_modm(S, hram, 64);
/* S = H(R,A,m)a */
expand256_modm(a, sk, 32);
mul256_modm(S, S, a);
/* S = (r + H(R,A,m)a) */
add256_modm(S, S, r);
/* S = (r + H(R,A,m)a) mod L */
contract256_modm(sig + 32, S);
return 0;
}
