1/* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 *
9 * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
10 */
11
12/* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b
13 *
14 * All curves taken from NIST recommendation paper of July 1999
15 * Available at http://csrc.nist.gov/cryptval/dss.htm
16 */
17#include "tomcrypt.h"
18
19/**
20  @file ecc_ansi_x963_export.c
21  ECC Crypto, Tom St Denis
22*/
23
24#ifdef MECC
25
26/** ECC X9.63 (Sec. 4.3.6) uncompressed export
27  @param key     Key to export
28  @param out     [out] destination of export
29  @param outlen  [in/out]  Length of destination and final output size
30  Return CRYPT_OK on success
31*/
32int ecc_ansi_x963_export(ecc_key *key, unsigned char *out, unsigned long *outlen)
33{
34   unsigned char buf[ECC_BUF_SIZE];
35   unsigned long numlen;
36
37   LTC_ARGCHK(key    != NULL);
38   LTC_ARGCHK(out    != NULL);
39   LTC_ARGCHK(outlen != NULL);
40
41   if (ltc_ecc_is_valid_idx(key->idx) == 0) {
42      return CRYPT_INVALID_ARG;
43   }
44   numlen = key->dp->size;
45
46   if (*outlen < (1 + 2*numlen)) {
47      *outlen = 1 + 2*numlen;
48      return CRYPT_BUFFER_OVERFLOW;
49   }
50
51   /* store byte 0x04 */
52   out[0] = 0x04;
53
54   /* pad and store x */
55   zeromem(buf, sizeof(buf));
56   mp_to_unsigned_bin(key->pubkey.x, buf + (numlen - mp_unsigned_bin_size(key->pubkey.x)));
57   XMEMCPY(out+1, buf, numlen);
58
59   /* pad and store y */
60   zeromem(buf, sizeof(buf));
61   mp_to_unsigned_bin(key->pubkey.y, buf + (numlen - mp_unsigned_bin_size(key->pubkey.y)));
62   XMEMCPY(out+1+numlen, buf, numlen);
63
64   *outlen = 1 + 2*numlen;
65   return CRYPT_OK;
66}
67
68#endif
69
70/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_ansi_x963_export.c,v $ */
71/* $Revision: 1.4 $ */
72/* $Date: 2006/12/04 02:50:11 $ */
73