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OpenAssetTools/thirdparty/libtomcrypt/pk/ecc/ecc_ansi_x963_export.c

78 lines
2.0 KiB
C

/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*/
/* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b
*
* All curves taken from NIST recommendation paper of July 1999
* Available at http://csrc.nist.gov/cryptval/dss.htm
*/
#include "tomcrypt.h"
/**
@file ecc_ansi_x963_export.c
ECC Crypto, Tom St Denis
*/
#ifdef LTC_MECC
/** ECC X9.63 (Sec. 4.3.6) uncompressed export
@param key Key to export
@param out [out] destination of export
@param outlen [in/out] Length of destination and final output size
Return CRYPT_OK on success
*/
int ecc_ansi_x963_export(ecc_key *key, unsigned char *out, unsigned long *outlen)
{
unsigned char buf[ECC_BUF_SIZE];
unsigned long numlen, xlen, ylen;
LTC_ARGCHK(key != NULL);
LTC_ARGCHK(outlen != NULL);
if (ltc_ecc_is_valid_idx(key->idx) == 0) {
return CRYPT_INVALID_ARG;
}
numlen = key->dp->size;
xlen = mp_unsigned_bin_size(key->pubkey.x);
ylen = mp_unsigned_bin_size(key->pubkey.y);
if (xlen > numlen || ylen > numlen || sizeof(buf) < numlen) {
return CRYPT_BUFFER_OVERFLOW;
}
if (*outlen < (1 + 2*numlen)) {
*outlen = 1 + 2*numlen;
return CRYPT_BUFFER_OVERFLOW;
}
LTC_ARGCHK(out != NULL);
/* store byte 0x04 */
out[0] = 0x04;
/* pad and store x */
zeromem(buf, sizeof(buf));
mp_to_unsigned_bin(key->pubkey.x, buf + (numlen - xlen));
XMEMCPY(out+1, buf, numlen);
/* pad and store y */
zeromem(buf, sizeof(buf));
mp_to_unsigned_bin(key->pubkey.y, buf + (numlen - ylen));
XMEMCPY(out+1+numlen, buf, numlen);
*outlen = 1 + 2*numlen;
return CRYPT_OK;
}
#endif
/* ref: HEAD -> master, tag: v1.18.2 */
/* git commit: 7e7eb695d581782f04b24dc444cbfde86af59853 */
/* commit time: 2018-07-01 22:49:01 +0200 */