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annotate src/pk/rsa/rsa_exptmod.c @ 380:d5faf4814ddb libtomcrypt-orig libtomcrypt-1.16

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Update to LibTomCrypt 1.16
author Matt Johnston <matt@ucc.asn.au>
date Thu, 11 Jan 2007 02:22:00 +0000
parents 59400faa4b44
children
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rev   line source
280
59400faa4b44 Re-import libtomcrypt 1.05 for cleaner propagating.
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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 rsa_exptmod.c
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15 RSA PKCS exptmod, Tom St Denis
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16 */
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17
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18 #ifdef MRSA
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19
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20 /**
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21 Compute an RSA modular exponentiation
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22 @param in The input data to send into RSA
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23 @param inlen The length of the input (octets)
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24 @param out [out] The destination
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25 @param outlen [in/out] The max size and resulting size of the output
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26 @param which Which exponent to use, e.g. PK_PRIVATE or PK_PUBLIC
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27 @param key The RSA key to use
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28 @return CRYPT_OK if successful
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29 */
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30 int rsa_exptmod(const unsigned char *in, unsigned long inlen,
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31 unsigned char *out, unsigned long *outlen, int which,
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32 rsa_key *key)
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33 {
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34 void *tmp, *tmpa, *tmpb;
280
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35 unsigned long x;
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36 int err;
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37
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38 LTC_ARGCHK(in != NULL);
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39 LTC_ARGCHK(out != NULL);
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40 LTC_ARGCHK(outlen != NULL);
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41 LTC_ARGCHK(key != NULL);
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42
280
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43 /* is the key of the right type for the operation? */
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44 if (which == PK_PRIVATE && (key->type != PK_PRIVATE)) {
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45 return CRYPT_PK_NOT_PRIVATE;
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46 }
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47
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48 /* must be a private or public operation */
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49 if (which != PK_PRIVATE && which != PK_PUBLIC) {
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50 return CRYPT_PK_INVALID_TYPE;
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51 }
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52
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53 /* init and copy into tmp */
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54 if ((err = mp_init_multi(&tmp, &tmpa, &tmpb, NULL)) != CRYPT_OK) { return err; }
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55 if ((err = mp_read_unsigned_bin(tmp, (unsigned char *)in, (int)inlen)) != CRYPT_OK) { goto error; }
280
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56
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57 /* sanity check on the input */
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58 if (mp_cmp(key->N, tmp) == LTC_MP_LT) {
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59 err = CRYPT_PK_INVALID_SIZE;
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60 goto error;
280
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61 }
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62
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63 /* are we using the private exponent and is the key optimized? */
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64 if (which == PK_PRIVATE) {
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65 /* tmpa = tmp^dP mod p */
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66 if ((err = mp_exptmod(tmp, key->dP, key->p, tmpa)) != CRYPT_OK) { goto error; }
280
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67
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68 /* tmpb = tmp^dQ mod q */
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69 if ((err = mp_exptmod(tmp, key->dQ, key->q, tmpb)) != CRYPT_OK) { goto error; }
280
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70
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71 /* tmp = (tmpa - tmpb) * qInv (mod p) */
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72 if ((err = mp_sub(tmpa, tmpb, tmp)) != CRYPT_OK) { goto error; }
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73 if ((err = mp_mulmod(tmp, key->qP, key->p, tmp)) != CRYPT_OK) { goto error; }
280
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74
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75 /* tmp = tmpb + q * tmp */
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76 if ((err = mp_mul(tmp, key->q, tmp)) != CRYPT_OK) { goto error; }
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77 if ((err = mp_add(tmp, tmpb, tmp)) != CRYPT_OK) { goto error; }
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78 } else {
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79 /* exptmod it */
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80 if ((err = mp_exptmod(tmp, key->e, key->N, tmp)) != CRYPT_OK) { goto error; }
280
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81 }
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82
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83 /* read it back */
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84 x = (unsigned long)mp_unsigned_bin_size(key->N);
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85 if (x > *outlen) {
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86 *outlen = x;
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87 err = CRYPT_BUFFER_OVERFLOW;
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88 goto error;
280
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89 }
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90
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91 /* this should never happen ... */
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92 if (mp_unsigned_bin_size(tmp) > mp_unsigned_bin_size(key->N)) {
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93 err = CRYPT_ERROR;
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94 goto error;
280
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95 }
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96 *outlen = x;
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97
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98 /* convert it */
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99 zeromem(out, x);
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100 if ((err = mp_to_unsigned_bin(tmp, out+(x-mp_unsigned_bin_size(tmp)))) != CRYPT_OK) { goto error; }
280
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101
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102 /* clean up and return */
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103 err = CRYPT_OK;
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104 error:
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105 mp_clear_multi(tmp, tmpa, tmpb, NULL);
280
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106 return err;
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107 }
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108
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109 #endif
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110
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111 /* $Source: /cvs/libtom/libtomcrypt/src/pk/rsa/rsa_exptmod.c,v $ */
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112 /* $Revision: 1.16 $ */
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113 /* $Date: 2006/12/04 03:09:28 $ */