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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
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2 * |
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3 * LibTomCrypt is a library that provides various cryptographic |
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4 * algorithms in a highly modular and flexible manner. |
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5 * |
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6 * The library is free for all purposes without any express |
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7 * guarantee it works. |
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8 * |
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9 * Tom St Denis, [email protected], http://libtomcrypt.com |
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10 */ |
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11 #include "tomcrypt.h" |
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12 |
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13 /** |
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14 @file dsa_encrypt_key.c |
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15 DSA Crypto, Tom St Denis |
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16 */ |
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17 |
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18 #ifdef MDSA |
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19 |
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20 /** |
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21 Encrypt a symmetric key with DSA |
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22 @param in The symmetric key you want to encrypt |
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23 @param inlen The length of the key to encrypt (octets) |
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24 @param out [out] The destination for the ciphertext |
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25 @param outlen [in/out] The max size and resulting size of the ciphertext |
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26 @param prng An active PRNG state |
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27 @param wprng The index of the PRNG you wish to use |
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28 @param hash The index of the hash you want to use |
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29 @param key The DSA key you want to encrypt to |
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30 @return CRYPT_OK if successful |
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31 */ |
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32 int dsa_encrypt_key(const unsigned char *in, unsigned long inlen, |
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33 unsigned char *out, unsigned long *outlen, |
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34 prng_state *prng, int wprng, int hash, |
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35 dsa_key *key) |
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36 { |
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37 unsigned char *expt, *skey; |
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38 void *g_pub, *g_priv; |
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39 unsigned long x, y; |
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40 int err; |
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41 |
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42 LTC_ARGCHK(in != NULL); |
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43 LTC_ARGCHK(out != NULL); |
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44 LTC_ARGCHK(outlen != NULL); |
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45 LTC_ARGCHK(key != NULL); |
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46 |
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47 /* check that wprng/cipher/hash are not invalid */ |
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48 if ((err = prng_is_valid(wprng)) != CRYPT_OK) { |
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49 return err; |
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50 } |
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51 |
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52 if ((err = hash_is_valid(hash)) != CRYPT_OK) { |
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53 return err; |
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54 } |
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55 |
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56 if (inlen > hash_descriptor[hash].hashsize) { |
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57 return CRYPT_INVALID_HASH; |
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58 } |
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59 |
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60 /* make a random key and export the public copy */ |
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61 if ((err = mp_init_multi(&g_pub, &g_priv, NULL)) != CRYPT_OK) { |
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62 return err; |
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63 } |
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64 |
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65 expt = XMALLOC(mp_unsigned_bin_size(key->p) + 1); |
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66 skey = XMALLOC(MAXBLOCKSIZE); |
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67 if (expt == NULL || skey == NULL) { |
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68 if (expt != NULL) { |
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69 XFREE(expt); |
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70 } |
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71 if (skey != NULL) { |
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72 XFREE(skey); |
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73 } |
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74 mp_clear_multi(g_pub, g_priv, NULL); |
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75 return CRYPT_MEM; |
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76 } |
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77 |
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78 /* make a random x, g^x pair */ |
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79 x = mp_unsigned_bin_size(key->q); |
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80 if (prng_descriptor[wprng].read(expt, x, prng) != x) { |
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81 err = CRYPT_ERROR_READPRNG; |
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82 goto LBL_ERR; |
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83 } |
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84 |
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85 /* load x */ |
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86 if ((err = mp_read_unsigned_bin(g_priv, expt, x)) != CRYPT_OK) { |
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87 goto LBL_ERR; |
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88 } |
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89 |
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90 /* compute y */ |
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91 if ((err = mp_exptmod(key->g, g_priv, key->p, g_pub)) != CRYPT_OK) { |
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92 goto LBL_ERR; |
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93 } |
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94 |
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95 /* make random key */ |
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96 x = mp_unsigned_bin_size(key->p) + 1; |
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97 if ((err = dsa_shared_secret(g_priv, key->y, key, expt, &x)) != CRYPT_OK) { |
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98 goto LBL_ERR; |
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99 } |
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100 |
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101 y = MAXBLOCKSIZE; |
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102 if ((err = hash_memory(hash, expt, x, skey, &y)) != CRYPT_OK) { |
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103 goto LBL_ERR; |
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104 } |
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105 |
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106 /* Encrypt key */ |
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107 for (x = 0; x < inlen; x++) { |
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108 skey[x] ^= in[x]; |
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109 } |
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110 |
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111 err = der_encode_sequence_multi(out, outlen, |
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112 LTC_ASN1_OBJECT_IDENTIFIER, hash_descriptor[hash].OIDlen, hash_descriptor[hash].OID, |
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113 LTC_ASN1_INTEGER, 1UL, g_pub, |
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114 LTC_ASN1_OCTET_STRING, inlen, skey, |
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115 LTC_ASN1_EOL, 0UL, NULL); |
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116 |
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117 LBL_ERR: |
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118 #ifdef LTC_CLEAN_STACK |
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119 /* clean up */ |
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120 zeromem(expt, mp_unsigned_bin_size(key->p) + 1); |
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121 zeromem(skey, MAXBLOCKSIZE); |
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122 #endif |
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123 |
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124 XFREE(skey); |
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125 XFREE(expt); |
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126 |
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127 mp_clear_multi(g_pub, g_priv, NULL); |
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128 return err; |
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129 } |
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130 |
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131 #endif |
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132 /* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_encrypt_key.c,v $ */ |
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133 /* $Revision: 1.7 $ */ |
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134 /* $Date: 2006/12/04 03:18:43 $ */ |
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135 |
