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_sign_hash.c 21 ECC Crypto, Tom St Denis 22 */ 23 24 #ifdef MECC 25 26 /** 27 Sign a message digest 28 @param in The message digest to sign 29 @param inlen The length of the digest 30 @param out [out] The destination for the signature 31 @param outlen [in/out] The max size and resulting size of the signature 32 @param prng An active PRNG state 33 @param wprng The index of the PRNG you wish to use 34 @param key A private ECC key 35 @return CRYPT_OK if successful 36 */ 37 int ecc_sign_hash(const unsigned char *in, unsigned long inlen, 38 unsigned char *out, unsigned long *outlen, 39 prng_state *prng, int wprng, ecc_key *key) 40 { 41 ecc_key pubkey; 42 void *r, *s, *e, *p; 43 int err; 44 45 LTC_ARGCHK(in != NULL); 46 LTC_ARGCHK(out != NULL); 47 LTC_ARGCHK(outlen != NULL); 48 LTC_ARGCHK(key != NULL); 49 50 /* is this a private key? */ 51 if (key->type != PK_PRIVATE) { 52 return CRYPT_PK_NOT_PRIVATE; 53 } 54 55 /* is the IDX valid ? */ 56 if (ltc_ecc_is_valid_idx(key->idx) != 1) { 57 return CRYPT_PK_INVALID_TYPE; 58 } 59 60 if ((err = prng_is_valid(wprng)) != CRYPT_OK) { 61 return err; 62 } 63 64 /* get the hash and load it as a bignum into 'e' */ 65 /* init the bignums */ 66 if ((err = mp_init_multi(&r, &s, &p, &e, NULL)) != CRYPT_OK) { 67 return err; 68 } 69 if ((err = mp_read_radix(p, (char *)key->dp->order, 16)) != CRYPT_OK) { goto errnokey; } 70 if ((err = mp_read_unsigned_bin(e, (unsigned char *)in, (int)inlen)) != CRYPT_OK) { goto errnokey; } 71 72 /* make up a key and export the public copy */ 73 for (;;) { 74 if ((err = ecc_make_key_ex(prng, wprng, &pubkey, key->dp)) != CRYPT_OK) { 75 goto errnokey; 76 } 77 78 /* find r = x1 mod n */ 79 if ((err = mp_mod(pubkey.pubkey.x, p, r)) != CRYPT_OK) { goto error; } 80 81 if (mp_iszero(r) == LTC_MP_YES) { 82 ecc_free(&pubkey); 83 } else { 84 /* find s = (e + xr)/k */ 85 if ((err = mp_invmod(pubkey.k, p, pubkey.k)) != CRYPT_OK) { goto error; } /* k = 1/k */ 86 if ((err = mp_mulmod(key->k, r, p, s)) != CRYPT_OK) { goto error; } /* s = xr */ 87 if ((err = mp_add(e, s, s)) != CRYPT_OK) { goto error; } /* s = e + xr */ 88 if ((err = mp_mod(s, p, s)) != CRYPT_OK) { goto error; } /* s = e + xr */ 89 if ((err = mp_mulmod(s, pubkey.k, p, s)) != CRYPT_OK) { goto error; } /* s = (e + xr)/k */ 90 ecc_free(&pubkey); 91 if (mp_iszero(s) == LTC_MP_NO) { 92 break; 93 } 94 } 95 } 96 97 /* store as SEQUENCE { r, s -- integer } */ 98 err = der_encode_sequence_multi(out, outlen, 99 LTC_ASN1_INTEGER, 1UL, r, 100 LTC_ASN1_INTEGER, 1UL, s, 101 LTC_ASN1_EOL, 0UL, NULL); 102 goto errnokey; 103 error: 104 ecc_free(&pubkey); 105 errnokey: 106 mp_clear_multi(r, s, p, e, NULL); 107 return err; 108 } 109 110 #endif 111 /* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_sign_hash.c,v $ */ 112 /* $Revision: 1.9 $ */ 113 /* $Date: 2006/12/04 02:50:11 $ */ 114 115
