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_import.c 21 ECC Crypto, Tom St Denis 22 */ 23 24 #ifdef MECC 25 26 static int is_point(ecc_key *key) 27 { 28 void *prime, *b, *t1, *t2; 29 int err; 30 31 if ((err = mp_init_multi(&prime, &b, &t1, &t2, NULL)) != CRYPT_OK) { 32 return err; 33 } 34 35 /* load prime and b */ 36 if ((err = mp_read_radix(prime, key->dp->prime, 16)) != CRYPT_OK) { goto error; } 37 if ((err = mp_read_radix(b, key->dp->B, 16)) != CRYPT_OK) { goto error; } 38 39 /* compute y^2 */ 40 if ((err = mp_sqr(key->pubkey.y, t1)) != CRYPT_OK) { goto error; } 41 42 /* compute x^3 */ 43 if ((err = mp_sqr(key->pubkey.x, t2)) != CRYPT_OK) { goto error; } 44 if ((err = mp_mod(t2, prime, t2)) != CRYPT_OK) { goto error; } 45 if ((err = mp_mul(key->pubkey.x, t2, t2)) != CRYPT_OK) { goto error; } 46 47 /* compute y^2 - x^3 */ 48 if ((err = mp_sub(t1, t2, t1)) != CRYPT_OK) { goto error; } 49 50 /* compute y^2 - x^3 + 3x */ 51 if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; } 52 if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; } 53 if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; } 54 if ((err = mp_mod(t1, prime, t1)) != CRYPT_OK) { goto error; } 55 while (mp_cmp_d(t1, 0) == LTC_MP_LT) { 56 if ((err = mp_add(t1, prime, t1)) != CRYPT_OK) { goto error; } 57 } 58 while (mp_cmp(t1, prime) != LTC_MP_LT) { 59 if ((err = mp_sub(t1, prime, t1)) != CRYPT_OK) { goto error; } 60 } 61 62 /* compare to b */ 63 if (mp_cmp(t1, b) != LTC_MP_EQ) { 64 err = CRYPT_INVALID_PACKET; 65 } else { 66 err = CRYPT_OK; 67 } 68 69 error: 70 mp_clear_multi(prime, b, t1, t2, NULL); 71 return err; 72 } 73 74 /** 75 Import an ECC key from a binary packet 76 @param in The packet to import 77 @param inlen The length of the packet 78 @param key [out] The destination of the import 79 @return CRYPT_OK if successful, upon error all allocated memory will be freed 80 */ 81 int ecc_import(const unsigned char *in, unsigned long inlen, ecc_key *key) 82 { 83 return ecc_import_ex(in, inlen, key, NULL); 84 } 85 86 /** 87 Import an ECC key from a binary packet, using user supplied domain params rather than one of the NIST ones 88 @param in The packet to import 89 @param inlen The length of the packet 90 @param key [out] The destination of the import 91 @param dp pointer to user supplied params; must be the same as the params used when exporting 92 @return CRYPT_OK if successful, upon error all allocated memory will be freed 93 */ 94 int ecc_import_ex(const unsigned char *in, unsigned long inlen, ecc_key *key, const ltc_ecc_set_type *dp) 95 { 96 unsigned long key_size; 97 unsigned char flags[1]; 98 int err; 99 100 LTC_ARGCHK(in != NULL); 101 LTC_ARGCHK(key != NULL); 102 LTC_ARGCHK(ltc_mp.name != NULL); 103 104 /* init key */ 105 if (mp_init_multi(&key->pubkey.x, &key->pubkey.y, &key->pubkey.z, &key->k, NULL) != CRYPT_OK) { 106 return CRYPT_MEM; 107 } 108 109 /* find out what type of key it is */ 110 if ((err = der_decode_sequence_multi(in, inlen, 111 LTC_ASN1_BIT_STRING, 1UL, &flags, 112 LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) { 113 goto done; 114 } 115 116 117 if (flags[0] == 1) { 118 /* private key */ 119 key->type = PK_PRIVATE; 120 if ((err = der_decode_sequence_multi(in, inlen, 121 LTC_ASN1_BIT_STRING, 1UL, flags, 122 LTC_ASN1_SHORT_INTEGER, 1UL, &key_size, 123 LTC_ASN1_INTEGER, 1UL, key->pubkey.x, 124 LTC_ASN1_INTEGER, 1UL, key->pubkey.y, 125 LTC_ASN1_INTEGER, 1UL, key->k, 126 LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) { 127 goto done; 128 } 129 } else { 130 /* public key */ 131 key->type = PK_PUBLIC; 132 if ((err = der_decode_sequence_multi(in, inlen, 133 LTC_ASN1_BIT_STRING, 1UL, flags, 134 LTC_ASN1_SHORT_INTEGER, 1UL, &key_size, 135 LTC_ASN1_INTEGER, 1UL, key->pubkey.x, 136 LTC_ASN1_INTEGER, 1UL, key->pubkey.y, 137 LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) { 138 goto done; 139 } 140 } 141 142 if (dp == NULL) { 143 /* find the idx */ 144 for (key->idx = 0; ltc_ecc_sets[key->idx].size && (unsigned long)ltc_ecc_sets[key->idx].size != key_size; ++key->idx); 145 if (ltc_ecc_sets[key->idx].size == 0) { 146 err = CRYPT_INVALID_PACKET; 147 goto done; 148 } 149 key->dp = <c_ecc_sets[key->idx]; 150 } else { 151 key->idx = -1; 152 key->dp = dp; 153 } 154 /* set z */ 155 if ((err = mp_set(key->pubkey.z, 1)) != CRYPT_OK) { goto done; } 156 157 /* is it a point on the curve? */ 158 if ((err = is_point(key)) != CRYPT_OK) { 159 goto done; 160 } 161 162 /* we're good */ 163 return CRYPT_OK; 164 done: 165 mp_clear_multi(key->pubkey.x, key->pubkey.y, key->pubkey.z, key->k, NULL); 166 return err; 167 } 168 #endif 169 /* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_import.c,v $ */ 170 /* $Revision: 1.11 $ */ 171 /* $Date: 2006/12/04 02:19:48 $ */ 172 173
