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added support for getting public key from a private key.

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mog 2013-09-05 03:57:26 -05:00
parent 4593b3f636
commit c87691205b
2 changed files with 21 additions and 0 deletions
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20
ecdsa.c
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@ -513,3 +513,23 @@ void ecdsa_sign(uint8_t *priv_key, uint8_t *msg, uint32_t msg_len, uint8_t *sig,
sig[1] = i;
*sig_len = i + 2;
}
void ecdsa_pubkey(uint8_t *priv_key, uint8_t *public_key_x, uint8_t *public_key_y)
{
uint32_t i;
uint64_t temp;
curve_point G;
bignum256 da;
temp = 0;
for (i = 0; i < 8; i++) {
temp += (((uint64_t)read_be(priv_key + (7 - i) * 4)) << (2 * i));
da.val[i] = temp & 0x3FFFFFFF;
temp >>= 30;
}
da.val[8] = temp;
scalar_multiply(&da, &G);
write_der(&G.x, public_key_x);
write_der(&G.y, public_key_y);
}

1
ecdsa.h
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@ -28,5 +28,6 @@
// uses secp256k1 curve
void ecdsa_sign(uint8_t *priv_key, uint8_t *msg, uint32_t msg_len, uint8_t *sig, uint32_t *sig_len);
void ecdsa_pubkey(uint8_t *priv_key, uint8_t *public_key_x, uint8_t *public_key_y);
#endif