10e577e24a
...someone could then do something like this...
unsigned char* out = NULL;
unsigned long len = 0;
while(ecc_ansi_x963_export(key, out, &len) == CRYPT_BUFFER_OVERFLOW &&
len == 0) {
out = malloc(len);
}
...as if someone would ever like to do something like that...
80 lines
1.9 KiB
C
80 lines
1.9 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@gmail.com, http://libtom.org
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*/
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/* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b
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*
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* All curves taken from NIST recommendation paper of July 1999
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* Available at http://csrc.nist.gov/cryptval/dss.htm
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*/
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#include "tomcrypt.h"
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/**
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@file ecc_ansi_x963_export.c
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ECC Crypto, Tom St Denis
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*/
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#ifdef LTC_MECC
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/** ECC X9.63 (Sec. 4.3.6) uncompressed export
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@param key Key to export
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@param out [out] destination of export
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@param outlen [in/out] Length of destination and final output size
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Return CRYPT_OK on success
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*/
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int ecc_ansi_x963_export(ecc_key *key, unsigned char *out, unsigned long *outlen)
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{
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unsigned char buf[ECC_BUF_SIZE];
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unsigned long numlen, xlen, ylen;
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LTC_ARGCHK(key != NULL);
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LTC_ARGCHK(outlen != NULL);
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if (ltc_ecc_is_valid_idx(key->idx) == 0) {
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return CRYPT_INVALID_ARG;
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}
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numlen = key->dp->size;
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xlen = mp_unsigned_bin_size(key->pubkey.x);
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ylen = mp_unsigned_bin_size(key->pubkey.y);
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if (xlen > numlen || ylen > numlen || sizeof(buf) < numlen) {
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return CRYPT_BUFFER_OVERFLOW;
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}
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if (*outlen < (1 + 2*numlen)) {
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*outlen = 1 + 2*numlen;
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return CRYPT_BUFFER_OVERFLOW;
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}
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LTC_ARGCHK(out != NULL);
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/* store byte 0x04 */
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out[0] = 0x04;
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/* pad and store x */
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zeromem(buf, sizeof(buf));
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mp_to_unsigned_bin(key->pubkey.x, buf + (numlen - xlen));
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XMEMCPY(out+1, buf, numlen);
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/* pad and store y */
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zeromem(buf, sizeof(buf));
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mp_to_unsigned_bin(key->pubkey.y, buf + (numlen - ylen));
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XMEMCPY(out+1+numlen, buf, numlen);
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*outlen = 1 + 2*numlen;
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return CRYPT_OK;
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}
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#endif
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/* $Source$ */
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/* $Revision$ */
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/* $Date$ */
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