/** Perform the curve25519 ECDH handshake with <b>skey</b> and <b>pkey</b>,
* writing CURVE25519_OUTPUT_LEN bytes of output into <b>output</b>. */
void
curve25519_handshake(uint8_t *output,
const curve25519_secret_key_t *skey,
const curve25519_public_key_t *pkey)
{
curve25519_impl(output, skey->secret_key, pkey->public_key);
}
STATIC int
curve25519_basepoint_impl(uint8_t *output, const uint8_t *secret)
{
int r = 0;
if (PREDICT_UNLIKELY(curve25519_use_ed == -1)) {
pick_curve25519_basepoint_impl();
}
/* TODO: Someone should benchmark curved25519_scalarmult_basepoint versus
* an optimized NaCl build to see which should be used when compiled with
* NaCl available. I suspected that the ed25519 optimization always wins.
*/
if (PREDICT_LIKELY(curve25519_use_ed == 1)) {
curved25519_scalarmult_basepoint_donna(output, secret);
r = 0;
} else {
static const uint8_t basepoint[32] = {9};
r = curve25519_impl(output, secret, basepoint);
}
return r;
}
static void
test_crypto_curve25519_impl(void *arg)
{
/* adapted from curve25519_donna, which adapted it from test-curve25519
version 20050915, by D. J. Bernstein, Public domain. */
const int randomize_high_bit = (arg != NULL);
#ifdef SLOW_CURVE25519_TEST
const int loop_max=10000;
const char e1_expected[] = "4faf81190869fd742a33691b0e0824d5"
"7e0329f4dd2819f5f32d130f1296b500";
const char e2k_expected[] = "05aec13f92286f3a781ccae98995a3b9"
"e0544770bc7de853b38f9100489e3e79";
const char e1e2k_expected[] = "cd6e8269104eb5aaee886bd2071fba88"
"bd13861475516bc2cd2b6e005e805064";
#else
const int loop_max=200;
const char e1_expected[] = "bc7112cde03f97ef7008cad1bdc56be3"
"c6a1037d74cceb3712e9206871dcf654";
const char e2k_expected[] = "dd8fa254fb60bdb5142fe05b1f5de44d"
"8e3ee1a63c7d14274ea5d4c67f065467";
const char e1e2k_expected[] = "7ddb98bd89025d2347776b33901b3e7e"
"c0ee98cb2257a4545c0cfb2ca3e1812b";
#endif
unsigned char e1k[32];
unsigned char e2k[32];
unsigned char e1e2k[32];
unsigned char e2e1k[32];
unsigned char e1[32] = {3};
unsigned char e2[32] = {5};
unsigned char k[32] = {9};
int loop, i;
char *mem_op_hex_tmp = NULL;
for (loop = 0; loop < loop_max; ++loop) {
curve25519_impl(e1k,e1,k);
curve25519_impl(e2e1k,e2,e1k);
curve25519_impl(e2k,e2,k);
if (randomize_high_bit) {
/* We require that the high bit of the public key be ignored. So if
* we're doing this variant test, we randomize the high bit of e2k, and
* make sure that the handshake still works out the same as it would
* otherwise. */
uint8_t byte;
crypto_rand((char*)&byte, 1);
e2k[31] |= (byte & 0x80);
}
curve25519_impl(e1e2k,e1,e2k);
test_memeq(e1e2k, e2e1k, 32);
if (loop == loop_max-1) {
break;
}
for (i = 0;i < 32;++i) e1[i] ^= e2k[i];
for (i = 0;i < 32;++i) e2[i] ^= e1k[i];
for (i = 0;i < 32;++i) k[i] ^= e1e2k[i];
}
test_memeq_hex(e1, e1_expected);
test_memeq_hex(e2k, e2k_expected);
test_memeq_hex(e1e2k, e1e2k_expected);
done:
tor_free(mem_op_hex_tmp);
}
