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148 lines
3.5 KiB
148 lines
3.5 KiB
/*
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Public domain by Andrew M. <liquidsun@gmail.com>
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Ed25519 reference implementation using Ed25519-donna
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*/
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#include "ed25519-donna.h"
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#include "ed25519.h"
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#include "ed25519-hash-custom.h"
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#include "curve25519-donna-scalarmult-base.h"
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/*
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Generates a (extsk[0..31]) and aExt (extsk[32..63])
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*/
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DONNA_INLINE static void
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ed25519_extsk(hash_512bits extsk, const ed25519_secret_key sk) {
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ed25519_hash(extsk, sk, 32);
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extsk[0] &= 248;
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extsk[31] &= 127;
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extsk[31] |= 64;
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}
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static void
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ed25519_hram(hash_512bits hram, const ed25519_signature RS, const ed25519_public_key pk, const unsigned char *m, size_t mlen) {
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ed25519_hash_context ctx;
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ed25519_hash_init(&ctx);
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ed25519_hash_update(&ctx, RS, 32);
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ed25519_hash_update(&ctx, pk, 32);
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ed25519_hash_update(&ctx, m, mlen);
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ed25519_hash_final(&ctx, hram);
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}
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void
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ed25519_publickey(const ed25519_secret_key sk, ed25519_public_key pk) {
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bignum256modm a;
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ge25519 ALIGN(16) A;
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hash_512bits extsk;
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/* A = aB */
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ed25519_extsk(extsk, sk);
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expand256_modm(a, extsk, 32);
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ge25519_scalarmult_base_niels(&A, ge25519_niels_base_multiples, a);
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ge25519_pack(pk, &A);
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}
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void
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ed25519_sign(const unsigned char *m, size_t mlen, const ed25519_secret_key sk, const ed25519_public_key pk, ed25519_signature RS) {
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ed25519_hash_context ctx;
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bignum256modm r, S, a;
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ge25519 ALIGN(16) R;
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hash_512bits extsk, hashr, hram;
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ed25519_extsk(extsk, sk);
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/* r = H(aExt[32..64], m) */
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ed25519_hash_init(&ctx);
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ed25519_hash_update(&ctx, extsk + 32, 32);
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ed25519_hash_update(&ctx, m, mlen);
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ed25519_hash_final(&ctx, hashr);
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expand256_modm(r, hashr, 64);
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/* R = rB */
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ge25519_scalarmult_base_niels(&R, ge25519_niels_base_multiples, r);
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ge25519_pack(RS, &R);
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/* S = H(R,A,m).. */
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ed25519_hram(hram, RS, pk, m, mlen);
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expand256_modm(S, hram, 64);
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/* S = H(R,A,m)a */
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expand256_modm(a, extsk, 32);
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mul256_modm(S, S, a);
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/* S = (r + H(R,A,m)a) */
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add256_modm(S, S, r);
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/* S = (r + H(R,A,m)a) mod L */
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contract256_modm(RS + 32, S);
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}
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int
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ed25519_sign_open(const unsigned char *m, size_t mlen, const ed25519_public_key pk, const ed25519_signature RS) {
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ge25519 ALIGN(16) R, A;
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hash_512bits hash;
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bignum256modm hram, S;
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unsigned char checkR[32];
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if ((RS[63] & 224) || !ge25519_unpack_negative_vartime(&A, pk))
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return -1;
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/* hram = H(R,A,m) */
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ed25519_hram(hash, RS, pk, m, mlen);
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expand256_modm(hram, hash, 64);
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/* S */
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expand256_modm(S, RS + 32, 32);
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/* SB - H(R,A,m)A */
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ge25519_double_scalarmult_vartime(&R, &A, hram, S);
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ge25519_pack(checkR, &R);
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/* check that R = SB - H(R,A,m)A */
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return ed25519_verify(RS, checkR, 32) ? 0 : -1;
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}
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/*
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Fast Curve25519 basepoint scalar multiplication
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*/
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void
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curve25519_scalarmult_basepoint(curve25519_key pk, const curve25519_key e) {
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curve25519_key ec;
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bignum256modm s;
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bignum25519 ALIGN(16) yplusz, zminusy;
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ge25519 ALIGN(16) p;
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size_t i;
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/* clamp */
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for (i = 0; i < 32; i++) ec[i] = e[i];
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ec[0] &= 248;
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ec[31] &= 127;
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ec[31] |= 64;
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expand_raw256_modm(s, ec);
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/* scalar * basepoint */
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ge25519_scalarmult_base_niels(&p, ge25519_niels_base_multiples, s);
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/* u = (y + z) / (z - y) */
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curve25519_add(yplusz, p.y, p.z);
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curve25519_sub(zminusy, p.z, p.y);
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curve25519_recip(zminusy, zminusy);
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curve25519_mul(yplusz, yplusz, zminusy);
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curve25519_contract(pk, yplusz);
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}
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void
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curve25519_scalarmult(curve25519_key mypublic, const curve25519_key secret, const curve25519_key basepoint) {
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curve25519_key e;
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size_t i;
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for (i = 0;i < 32;++i) e[i] = secret[i];
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e[0] &= 0xf8;
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e[31] &= 0x7f;
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e[31] |= 0x40;
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curve25519_scalarmult_donna(mypublic, e, basepoint);
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}
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