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