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_encrypt_key.c
21  ECC Crypto, Tom St Denis
22*/
23
24#ifdef MECC
25
26/**
27  Encrypt a symmetric key with ECC
28  @param in         The symmetric key you want to encrypt
29  @param inlen      The length of the key to encrypt (octets)
30  @param out        [out] The destination for the ciphertext
31  @param outlen     [in/out] The max size and resulting size of the ciphertext
32  @param prng       An active PRNG state
33  @param wprng      The index of the PRNG you wish to use
34  @param hash       The index of the hash you want to use
35  @param key        The ECC key you want to encrypt to
36  @return CRYPT_OK if successful
37*/
38int ecc_encrypt_key(const unsigned char *in,   unsigned long inlen,
39                          unsigned char *out,  unsigned long *outlen,
40                          prng_state *prng, int wprng, int hash,
41                          ecc_key *key)
42{
43    unsigned char *pub_expt, *ecc_shared, *skey;
44    ecc_key        pubkey;
45    unsigned long  x, y, pubkeysize;
46    int            err;
47
48    LTC_ARGCHK(in      != NULL);
49    LTC_ARGCHK(out     != NULL);
50    LTC_ARGCHK(outlen  != NULL);
51    LTC_ARGCHK(key     != NULL);
52
53    /* check that wprng/cipher/hash are not invalid */
54    if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
55       return err;
56    }
57
58    if ((err = hash_is_valid(hash)) != CRYPT_OK) {
59       return err;
60    }
61
62    if (inlen > hash_descriptor[hash].hashsize) {
63       return CRYPT_INVALID_HASH;
64    }
65
66    /* make a random key and export the public copy */
67    if ((err = ecc_make_key_ex(prng, wprng, &pubkey, key->dp)) != CRYPT_OK) {
68       return err;
69    }
70
71    pub_expt   = XMALLOC(ECC_BUF_SIZE);
72    ecc_shared = XMALLOC(ECC_BUF_SIZE);
73    skey       = XMALLOC(MAXBLOCKSIZE);
74    if (pub_expt == NULL || ecc_shared == NULL || skey == NULL) {
75       if (pub_expt != NULL) {
76          XFREE(pub_expt);
77       }
78       if (ecc_shared != NULL) {
79          XFREE(ecc_shared);
80       }
81       if (skey != NULL) {
82          XFREE(skey);
83       }
84       ecc_free(&pubkey);
85       return CRYPT_MEM;
86    }
87
88    pubkeysize = ECC_BUF_SIZE;
89    if ((err = ecc_export(pub_expt, &pubkeysize, PK_PUBLIC, &pubkey)) != CRYPT_OK) {
90       ecc_free(&pubkey);
91       goto LBL_ERR;
92    }
93
94    /* make random key */
95    x        = ECC_BUF_SIZE;
96    if ((err = ecc_shared_secret(&pubkey, key, ecc_shared, &x)) != CRYPT_OK) {
97       ecc_free(&pubkey);
98       goto LBL_ERR;
99    }
100    ecc_free(&pubkey);
101    y = MAXBLOCKSIZE;
102    if ((err = hash_memory(hash, ecc_shared, x, skey, &y)) != CRYPT_OK) {
103       goto LBL_ERR;
104    }
105
106    /* Encrypt key */
107    for (x = 0; x < inlen; x++) {
108      skey[x] ^= in[x];
109    }
110
111    err = der_encode_sequence_multi(out, outlen,
112                                    LTC_ASN1_OBJECT_IDENTIFIER,  hash_descriptor[hash].OIDlen,   hash_descriptor[hash].OID,
113                                    LTC_ASN1_OCTET_STRING,       pubkeysize,                     pub_expt,
114                                    LTC_ASN1_OCTET_STRING,       inlen,                          skey,
115                                    LTC_ASN1_EOL,                0UL,                            NULL);
116
117LBL_ERR:
118#ifdef LTC_CLEAN_STACK
119    /* clean up */
120    zeromem(pub_expt,   ECC_BUF_SIZE);
121    zeromem(ecc_shared, ECC_BUF_SIZE);
122    zeromem(skey,       MAXBLOCKSIZE);
123#endif
124
125    XFREE(skey);
126    XFREE(ecc_shared);
127    XFREE(pub_expt);
128
129    return err;
130}
131
132#endif
133/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_encrypt_key.c,v $ */
134/* $Revision: 1.4 $ */
135/* $Date: 2006/11/21 00:10:18 $ */
136
137