/* LibTomCrypt, modular cryptographic library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
#include "tomcrypt_private.h"
/**
@file x25519_shared_secret.c
Create a X25519 shared secret, Steffen Jaeckel
*/
#ifdef LTC_CURVE25519
/**
Create a X25519 shared secret.
@param private_key The private X25519 key in the pair
@param public_key The public X25519 key in the pair
@param out [out] The destination of the shared data
@param outlen [in/out] The max size and resulting size of the shared data.
@return CRYPT_OK if successful
*/
int x25519_shared_secret(const curve25519_key *private_key,
const curve25519_key *public_key,
unsigned char *out, unsigned long *outlen)
{
LTC_ARGCHK(private_key != NULL);
LTC_ARGCHK(public_key != NULL);
LTC_ARGCHK(out != NULL);
LTC_ARGCHK(outlen != NULL);
if(private_key->type != PK_PRIVATE) return CRYPT_PK_INVALID_TYPE;
if(*outlen < 32uL) {
*outlen = 32uL;
return CRYPT_BUFFER_OVERFLOW;
}
tweetnacl_crypto_scalarmult(out, private_key->priv, public_key->pub);
*outlen = 32uL;
return CRYPT_OK;
}
#endif