169 lines
3.8 KiB
C
169 lines
3.8 KiB
C
/* Edwards curve signature system
|
|
* Daniel Beer <dlbeer@gmail.com>, 22 Apr 2014
|
|
*
|
|
* This file is in the public domain.
|
|
*/
|
|
|
|
#include "ed25519.h"
|
|
#include "sha512.h"
|
|
#include "fprime.h"
|
|
#include "edsign.h"
|
|
|
|
#define EXPANDED_SIZE 64
|
|
|
|
static const uint8_t ed25519_order[FPRIME_SIZE] = {
|
|
0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58,
|
|
0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14,
|
|
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
|
|
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
|
|
};
|
|
|
|
static void expand_key(uint8_t *expanded, const uint8_t *secret)
|
|
{
|
|
struct sha512_state s;
|
|
|
|
sha512_init(&s);
|
|
sha512_final(&s, secret, EDSIGN_SECRET_KEY_SIZE);
|
|
sha512_get(&s, expanded, 0, EXPANDED_SIZE);
|
|
ed25519_prepare(expanded);
|
|
}
|
|
|
|
static uint8_t upp(struct ed25519_pt *p, const uint8_t *packed)
|
|
{
|
|
uint8_t x[F25519_SIZE];
|
|
uint8_t y[F25519_SIZE];
|
|
uint8_t ok = ed25519_try_unpack(x, y, packed);
|
|
|
|
ed25519_project(p, x, y);
|
|
return ok;
|
|
}
|
|
|
|
static void pp(uint8_t *packed, const struct ed25519_pt *p)
|
|
{
|
|
uint8_t x[F25519_SIZE];
|
|
uint8_t y[F25519_SIZE];
|
|
|
|
ed25519_unproject(x, y, p);
|
|
ed25519_pack(packed, x, y);
|
|
}
|
|
|
|
static void sm_pack(uint8_t *r, const uint8_t *k)
|
|
{
|
|
struct ed25519_pt p;
|
|
|
|
ed25519_smult(&p, &ed25519_base, k);
|
|
pp(r, &p);
|
|
}
|
|
|
|
void edsign_sec_to_pub(uint8_t *pub, const uint8_t *secret)
|
|
{
|
|
uint8_t expanded[EXPANDED_SIZE];
|
|
|
|
expand_key(expanded, secret);
|
|
sm_pack(pub, expanded);
|
|
}
|
|
|
|
static void hash_with_prefix(uint8_t *out_fp,
|
|
uint8_t *init_block, unsigned int prefix_size,
|
|
const uint8_t *message, size_t len)
|
|
{
|
|
struct sha512_state s;
|
|
|
|
sha512_init(&s);
|
|
|
|
if (len < SHA512_BLOCK_SIZE && len + prefix_size < SHA512_BLOCK_SIZE) {
|
|
memcpy(init_block + prefix_size, message, len);
|
|
sha512_final(&s, init_block, len + prefix_size);
|
|
} else {
|
|
size_t i;
|
|
|
|
memcpy(init_block + prefix_size, message,
|
|
SHA512_BLOCK_SIZE - prefix_size);
|
|
sha512_block(&s, init_block);
|
|
|
|
for (i = SHA512_BLOCK_SIZE - prefix_size;
|
|
i + SHA512_BLOCK_SIZE <= len;
|
|
i += SHA512_BLOCK_SIZE)
|
|
sha512_block(&s, message + i);
|
|
|
|
sha512_final(&s, message + i, len + prefix_size);
|
|
}
|
|
|
|
sha512_get(&s, init_block, 0, SHA512_HASH_SIZE);
|
|
fprime_from_bytes(out_fp, init_block, SHA512_HASH_SIZE, ed25519_order);
|
|
}
|
|
|
|
static void generate_k(uint8_t *k, const uint8_t *kgen_key,
|
|
const uint8_t *message, size_t len)
|
|
{
|
|
uint8_t block[SHA512_BLOCK_SIZE];
|
|
|
|
memcpy(block, kgen_key, 32);
|
|
hash_with_prefix(k, block, 32, message, len);
|
|
}
|
|
|
|
static void hash_message(uint8_t *z, const uint8_t *r, const uint8_t *a,
|
|
const uint8_t *m, size_t len)
|
|
{
|
|
uint8_t block[SHA512_BLOCK_SIZE];
|
|
|
|
memcpy(block, r, 32);
|
|
memcpy(block + 32, a, 32);
|
|
hash_with_prefix(z, block, 64, m, len);
|
|
}
|
|
|
|
void edsign_sign(uint8_t *signature, const uint8_t *pub,
|
|
const uint8_t *secret,
|
|
const uint8_t *message, size_t len)
|
|
{
|
|
uint8_t expanded[EXPANDED_SIZE];
|
|
uint8_t e[FPRIME_SIZE];
|
|
uint8_t s[FPRIME_SIZE];
|
|
uint8_t k[FPRIME_SIZE];
|
|
uint8_t z[FPRIME_SIZE];
|
|
|
|
expand_key(expanded, secret);
|
|
|
|
/* Generate k and R = kB */
|
|
generate_k(k, expanded + 32, message, len);
|
|
sm_pack(signature, k);
|
|
|
|
/* Compute z = H(R, A, M) */
|
|
hash_message(z, signature, pub, message, len);
|
|
|
|
/* Obtain e */
|
|
fprime_from_bytes(e, expanded, 32, ed25519_order);
|
|
|
|
/* Compute s = ze + k */
|
|
fprime_mul(s, z, e, ed25519_order);
|
|
fprime_add(s, k, ed25519_order);
|
|
memcpy(signature + 32, s, 32);
|
|
}
|
|
|
|
uint8_t edsign_verify(const uint8_t *signature, const uint8_t *pub,
|
|
const uint8_t *message, size_t len)
|
|
{
|
|
struct ed25519_pt p;
|
|
struct ed25519_pt q;
|
|
uint8_t lhs[F25519_SIZE];
|
|
uint8_t rhs[F25519_SIZE];
|
|
uint8_t z[FPRIME_SIZE];
|
|
uint8_t ok = 1;
|
|
|
|
/* Compute z = H(R, A, M) */
|
|
hash_message(z, signature, pub, message, len);
|
|
|
|
/* sB = (ze + k)B = ... */
|
|
sm_pack(lhs, signature + 32);
|
|
|
|
/* ... = zA + R */
|
|
ok &= upp(&p, pub);
|
|
ed25519_smult(&p, &p, z);
|
|
ok &= upp(&q, signature);
|
|
ed25519_add(&p, &p, &q);
|
|
pp(rhs, &p);
|
|
|
|
/* Equal? */
|
|
return ok & f25519_eq(lhs, rhs);
|
|
}
|