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 (at) 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 */ 38 int 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); 116 117 LBL_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
