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_make_key.c
21  ECC Crypto, Tom St Denis
22*/
23
24#ifdef MECC
25
26/**
27  Make a new ECC key
28  @param prng         An active PRNG state
29  @param wprng        The index of the PRNG you wish to use
30  @param keysize      The keysize for the new key (in octets from 20 to 65 bytes)
31  @param key          [out] Destination of the newly created key
32  @return CRYPT_OK if successful, upon error all allocated memory will be freed
33*/
34int ecc_make_key(prng_state *prng, int wprng, int keysize, ecc_key *key)
35{
36   int x, err;
37
38   /* find key size */
39   for (x = 0; (keysize > ltc_ecc_sets[x].size) && (ltc_ecc_sets[x].size != 0); x++);
40   keysize = ltc_ecc_sets[x].size;
41
42   if (keysize > ECC_MAXSIZE || ltc_ecc_sets[x].size == 0) {
43      return CRYPT_INVALID_KEYSIZE;
44   }
45   err = ecc_make_key_ex(prng, wprng, key, &ltc_ecc_sets[x]);
46   key->idx = x;
47   return err;
48}
49
50int ecc_make_key_ex(prng_state *prng, int wprng, ecc_key *key, const ltc_ecc_set_type *dp)
51{
52   int            err;
53   ecc_point     *base;
54   void          *prime;
55   unsigned char *buf;
56   int            keysize;
57
58   LTC_ARGCHK(key         != NULL);
59   LTC_ARGCHK(ltc_mp.name != NULL);
60   LTC_ARGCHK(dp          != NULL);
61
62   /* good prng? */
63   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
64      return err;
65   }
66
67   key->idx = -1;
68   key->dp  = dp;
69   keysize  = dp->size;
70
71   /* allocate ram */
72   base = NULL;
73   buf  = XMALLOC(ECC_MAXSIZE);
74   if (buf == NULL) {
75      return CRYPT_MEM;
76   }
77
78   /* make up random string */
79   if (prng_descriptor[wprng].read(buf, (unsigned long)keysize, prng) != (unsigned long)keysize) {
80      err = CRYPT_ERROR_READPRNG;
81      goto ERR_BUF;
82   }
83
84   /* setup the key variables */
85   if ((err = mp_init_multi(&key->pubkey.x, &key->pubkey.y, &key->pubkey.z, &key->k, &prime, NULL)) != CRYPT_OK) {
86      goto ERR_BUF;
87   }
88   base = ltc_ecc_new_point();
89   if (base == NULL) {
90      err = CRYPT_MEM;
91      goto errkey;
92   }
93
94   /* read in the specs for this key */
95   if ((err = mp_read_radix(prime,   (char *)key->dp->prime, 16)) != CRYPT_OK)                  { goto errkey; }
96   if ((err = mp_read_radix(base->x, (char *)key->dp->Gx, 16)) != CRYPT_OK)                     { goto errkey; }
97   if ((err = mp_read_radix(base->y, (char *)key->dp->Gy, 16)) != CRYPT_OK)                     { goto errkey; }
98   if ((err = mp_set(base->z, 1)) != CRYPT_OK)                                                  { goto errkey; }
99   if ((err = mp_read_unsigned_bin(key->k, (unsigned char *)buf, keysize)) != CRYPT_OK)         { goto errkey; }
100
101   /* make the public key */
102   if ((err = ltc_mp.ecc_ptmul(key->k, base, &key->pubkey, prime, 1)) != CRYPT_OK)              { goto errkey; }
103   key->type = PK_PRIVATE;
104
105   /* free up ram */
106   err = CRYPT_OK;
107   goto cleanup;
108errkey:
109   mp_clear_multi(key->pubkey.x, key->pubkey.y, key->pubkey.z, key->k, NULL);
110cleanup:
111   ltc_ecc_del_point(base);
112   mp_clear(prime);
113ERR_BUF:
114#ifdef LTC_CLEAN_STACK
115   zeromem(buf, ECC_MAXSIZE);
116#endif
117   XFREE(buf);
118   return err;
119}
120
121#endif
122/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_make_key.c,v $ */
123/* $Revision: 1.9 $ */
124/* $Date: 2006/12/04 02:50:11 $ */
125
126