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/*
Public domain by Andrew M. <liquidsun@gmail.com>
Ed25519 reference implementation using Ed25519-donna
*/
#define ED25519_FN(fn) cryptonite_##fn
#include "ed25519-donna.h"
#include "ed25519.h"
#include "ed25519-randombytes.h"
#include "ed25519-hash.h"
/*
Generates a (extsk[0..31]) and aExt (extsk[32..63])
*/
DONNA_INLINE static void
ed25519_extsk(hash_512bits extsk, const ed25519_secret_key sk) {
ed25519_hash(extsk, sk, 32);
extsk[0] &= 248;
extsk[31] &= 127;
extsk[31] |= 64;
}
static void
ed25519_hram(hash_512bits hram, const ed25519_signature RS, const ed25519_public_key pk, const unsigned char *m, size_t mlen) {
ed25519_hash_context ctx;
ed25519_hash_init(&ctx);
ed25519_hash_update(&ctx, RS, 32);
ed25519_hash_update(&ctx, pk, 32);
ed25519_hash_update(&ctx, m, mlen);
ed25519_hash_final(&ctx, hram);
}
void
ED25519_FN(ed25519_publickey) (const ed25519_secret_key sk, ed25519_public_key pk) {
bignum256modm a;
ge25519 ALIGN(16) 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);
}
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 ALIGN(16) 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);
}
int
ED25519_FN(ed25519_sign_open) (const unsigned char *m, size_t mlen, const ed25519_public_key pk, const ed25519_signature RS) {
ge25519 ALIGN(16) R, A;
hash_512bits hash;
bignum256modm hram, S;
unsigned char checkR[32];
if ((RS[63] & 224) || !ge25519_unpack_negative_vartime(&A, pk))
return -1;
/* hram = H(R,A,m) */
ed25519_hram(hash, RS, pk, m, mlen);
expand256_modm(hram, hash, 64);
/* S */
expand256_modm(S, RS + 32, 32);
/* SB - H(R,A,m)A */
ge25519_double_scalarmult_vartime(&R, &A, hram, S);
ge25519_pack(checkR, &R);
/* check that R = SB - H(R,A,m)A */
return ed25519_verify(RS, checkR, 32) ? 0 : -1;
}
#include "ed25519-donna-batchverify.h"
/*
Fast Curve25519 basepoint scalar multiplication
*/
void
ED25519_FN(curved25519_scalarmult_basepoint) (curved25519_key pk, const curved25519_key e) {
curved25519_key ec;
bignum256modm s;
bignum25519 ALIGN(16) yplusz, zminusy;
ge25519 ALIGN(16) 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);
}
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