Mercurial > dropbear
annotate src/pk/rsa/rsa_exptmod.c @ 191:1c15b283127b libtomcrypt-orig
Import of libtomcrypt 1.02 with manual path rename rearrangement etc
author | Matt Johnston <matt@ucc.asn.au> |
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date | Fri, 06 May 2005 13:23:02 +0000 |
parents | |
children | 39d5d58461d6 |
rev | line source |
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191
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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.org |
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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 mp_int tmp, tmpa, tmpb; |
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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 |
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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)) != MP_OKAY) { return mpi_to_ltc_error(err); } |
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55 if ((err = mp_read_unsigned_bin(&tmp, (unsigned char *)in, (int)inlen)) != MP_OKAY) { goto error; } |
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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) == MP_LT) { |
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59 err = CRYPT_PK_INVALID_SIZE; |
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60 goto done; |
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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)) != MP_OKAY) { goto error; } |
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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)) != MP_OKAY) { goto error; } |
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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)) != MP_OKAY) { goto error; } |
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73 if ((err = mp_mulmod(&tmp, &key->qP, &key->p, &tmp)) != MP_OKAY) { goto error; } |
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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)) != MP_OKAY) { goto error; } |
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77 if ((err = mp_add(&tmp, &tmpb, &tmp)) != MP_OKAY) { 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)) != MP_OKAY) { goto error; } |
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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 err = CRYPT_BUFFER_OVERFLOW; |
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87 goto done; |
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88 } |
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89 *outlen = x; |
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90 |
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91 /* convert it */ |
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92 zeromem(out, x); |
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93 if ((err = mp_to_unsigned_bin(&tmp, out+(x-mp_unsigned_bin_size(&tmp)))) != MP_OKAY) { goto error; } |
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94 |
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95 /* clean up and return */ |
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96 err = CRYPT_OK; |
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97 goto done; |
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98 error: |
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99 err = mpi_to_ltc_error(err); |
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100 done: |
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101 mp_clear_multi(&tmp, &tmpa, &tmpb, NULL); |
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102 return err; |
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103 } |
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104 |
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105 #endif |