49 lines
1.1 KiB
C
49 lines
1.1 KiB
C
|
/* Curve25519 (Montgomery form)
|
||
|
|
* Daniel Beer <dlbeer@gmail.com>, 18 Apr 2014
|
||
|
|
*
|
||
|
|
* This file is in the public domain.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#ifndef C25519_H_
|
||
|
|
#define C25519_H_
|
||
|
|
|
||
|
|
#include <stdint.h>
|
||
|
|
#include "f25519.h"
|
||
|
|
|
||
|
|
/* Curve25519 has the equation over F(p = 2^255-19):
|
||
|
|
*
|
||
|
|
* y^2 = x^3 + 486662x^2 + x
|
||
|
|
*
|
||
|
|
* 486662 = 4A+2, where A = 121665. This is a Montgomery curve.
|
||
|
|
*
|
||
|
|
* For more information, see:
|
||
|
|
*
|
||
|
|
* Bernstein, D.J. (2006) "Curve25519: New Diffie-Hellman speed
|
||
|
|
* records". Document ID: 4230efdfa673480fc079449d90f322c0.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* This is the site of a Curve25519 exponent (private key) */
|
||
|
|
#define C25519_EXPONENT_SIZE 32
|
||
|
|
|
||
|
|
/* Having generated 32 random bytes, you should call this function to
|
||
|
|
* finalize the generated key.
|
||
|
|
*/
|
||
|
|
static inline void c25519_prepare(uint8_t *key)
|
||
|
|
{
|
||
|
|
key[0] &= 0xf8;
|
||
|
|
key[31] &= 0x7f;
|
||
|
|
key[31] |= 0x40;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* X-coordinate of the base point */
|
||
|
|
extern const uint8_t c25519_base_x[F25519_SIZE];
|
||
|
|
|
||
|
|
/* X-coordinate scalar multiply: given the X-coordinate of q, return the
|
||
|
|
* X-coordinate of e*q.
|
||
|
|
*
|
||
|
|
* result and q are field elements. e is an exponent.
|
||
|
|
*/
|
||
|
|
void c25519_smult(uint8_t *result, const uint8_t *q, const uint8_t *e);
|
||
|
|
|
||
|
|
#endif
|