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annotate src/modes/ctr/ctr_encrypt.c @ 209:39d5d58461d6 libtomcrypt-orig LTC_1.05

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Import of libtomcrypt 1.05
author Matt Johnston <matt@ucc.asn.au>
date Wed, 06 Jul 2005 03:53:40 +0000
parents 1c15b283127b
children
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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 ctr_encrypt.c
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15 CTR implementation, encrypt data, Tom St Denis
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16 */
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17
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18
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19 #ifdef CTR
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20
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21 /**
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22 CTR encrypt
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23 @param pt Plaintext
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24 @param ct [out] Ciphertext
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25 @param len Length of plaintext (octets)
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26 @param ctr CTR state
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27 @return CRYPT_OK if successful
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28 */
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29 int ctr_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CTR *ctr)
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30 {
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31 int x, err;
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32
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33 LTC_ARGCHK(pt != NULL);
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34 LTC_ARGCHK(ct != NULL);
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35 LTC_ARGCHK(ctr != NULL);
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36
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37 if ((err = cipher_is_valid(ctr->cipher)) != CRYPT_OK) {
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38 return err;
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39 }
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40
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41 /* is blocklen/padlen valid? */
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42 if (ctr->blocklen < 0 || ctr->blocklen > (int)sizeof(ctr->ctr) ||
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43 ctr->padlen < 0 || ctr->padlen > (int)sizeof(ctr->pad)) {
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44 return CRYPT_INVALID_ARG;
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45 }
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46
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47 #ifdef LTC_FAST
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48 if (ctr->blocklen % sizeof(LTC_FAST_TYPE)) {
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49 return CRYPT_INVALID_ARG;
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50 }
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51 #endif
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52
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53 /* handle acceleration only if pad is empty, accelerator is present and length is >= a block size */
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54 if ((ctr->padlen == ctr->blocklen) && cipher_descriptor[ctr->cipher].accel_ctr_encrypt != NULL && (len >= (unsigned long)ctr->blocklen)) {
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55 cipher_descriptor[ctr->cipher].accel_ctr_encrypt(pt, ct, len/ctr->blocklen, ctr->ctr, ctr->mode, &ctr->key);
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56 len %= ctr->blocklen;
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57 }
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58
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59 while (len) {
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60 /* is the pad empty? */
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61 if (ctr->padlen == ctr->blocklen) {
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62 /* increment counter */
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63 if (ctr->mode == CTR_COUNTER_LITTLE_ENDIAN) {
191
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64 /* little-endian */
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65 for (x = 0; x < ctr->blocklen; x++) {
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66 ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
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67 if (ctr->ctr[x] != (unsigned char)0) {
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68 break;
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69 }
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70 }
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71 } else {
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72 /* big-endian */
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73 for (x = ctr->blocklen-1; x >= 0; x--) {
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74 ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
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75 if (ctr->ctr[x] != (unsigned char)0) {
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76 break;
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77 }
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78 }
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79 }
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80
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81 /* encrypt it */
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82 cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key);
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83 ctr->padlen = 0;
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84 }
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85 #ifdef LTC_FAST
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86 if (ctr->padlen == 0 && len >= (unsigned long)ctr->blocklen) {
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87 for (x = 0; x < ctr->blocklen; x += sizeof(LTC_FAST_TYPE)) {
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88 *((LTC_FAST_TYPE*)((unsigned char *)ct + x)) = *((LTC_FAST_TYPE*)((unsigned char *)pt + x)) ^
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89 *((LTC_FAST_TYPE*)((unsigned char *)ctr->pad + x));
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90 }
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91 pt += ctr->blocklen;
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92 ct += ctr->blocklen;
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93 len -= ctr->blocklen;
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94 ctr->padlen = ctr->blocklen;
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95 continue;
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96 }
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97 #endif
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98 *ct++ = *pt++ ^ ctr->pad[ctr->padlen++];
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99 --len;
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100 }
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101 return CRYPT_OK;
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102 }
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103
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104 #endif
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105
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106 /* $Source: /cvs/libtom/libtomcrypt/src/modes/ctr/ctr_encrypt.c,v $ */
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107 /* $Revision: 1.13 $ */
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108 /* $Date: 2005/05/05 14:35:59 $ */