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@gmail.com, http://libtomcrypt.com
10 */
11#include "tomcrypt.h"
12
13/**
14   @file lrw_process.c
15   LRW_MODE implementation, Encrypt/decrypt blocks, Tom St Denis
16*/
17
18#ifdef LTC_LRW_MODE
19
20/**
21  Process blocks with LRW, since decrypt/encrypt are largely the same they share this code.
22  @param pt        The "input" data
23  @param ct        [out] The "output" data
24  @param len       The length of the input, must be a multiple of 128-bits (16 octets)
25  @param mode      LRW_ENCRYPT or LRW_DECRYPT
26  @param lrw       The LRW state
27  @return  CRYPT_OK if successful
28*/
29int lrw_process(const unsigned char *pt, unsigned char *ct, unsigned long len, int mode, symmetric_LRW *lrw)
30{
31   unsigned char prod[16];
32   int           x, err;
33#ifdef LRW_TABLES
34   int           y;
35#endif
36
37   LTC_ARGCHK(pt  != NULL);
38   LTC_ARGCHK(ct  != NULL);
39   LTC_ARGCHK(lrw != NULL);
40
41   if (len & 15) {
42      return CRYPT_INVALID_ARG;
43   }
44
45   while (len) {
46      /* copy pad */
47      XMEMCPY(prod, lrw->pad, 16);
48
49      /* increment IV */
50      for (x = 15; x >= 0; x--) {
51          lrw->IV[x] = (lrw->IV[x] + 1) & 255;
52          if (lrw->IV[x]) {
53              break;
54          }
55      }
56
57      /* update pad */
58#ifdef LRW_TABLES
59      /* for each byte changed we undo it's affect on the pad then add the new product */
60      for (; x < 16; x++) {
61#ifdef LTC_FAST
62          for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
63              *((LTC_FAST_TYPE *)(lrw->pad + y)) ^= *((LTC_FAST_TYPE *)(&lrw->PC[x][lrw->IV[x]][y])) ^ *((LTC_FAST_TYPE *)(&lrw->PC[x][(lrw->IV[x]-1)&255][y]));
64          }
65#else
66          for (y = 0; y < 16; y++) {
67              lrw->pad[y] ^= lrw->PC[x][lrw->IV[x]][y] ^ lrw->PC[x][(lrw->IV[x]-1)&255][y];
68          }
69#endif
70      }
71#else
72      gcm_gf_mult(lrw->tweak, lrw->IV, lrw->pad);
73#endif
74
75      /* xor prod */
76#ifdef LTC_FAST
77      for (x = 0; x < 16; x += sizeof(LTC_FAST_TYPE)) {
78           *((LTC_FAST_TYPE *)(ct + x)) = *((LTC_FAST_TYPE *)(pt + x)) ^ *((LTC_FAST_TYPE *)(prod + x));
79      }
80#else
81      for (x = 0; x < 16; x++) {
82         ct[x] = pt[x] ^ prod[x];
83      }
84#endif
85
86      /* send through cipher */
87      if (mode == LRW_ENCRYPT) {
88         if ((err = cipher_descriptor[lrw->cipher].ecb_encrypt(ct, ct, &lrw->key)) != CRYPT_OK) {
89            return err;
90         }
91      } else {
92         if ((err = cipher_descriptor[lrw->cipher].ecb_decrypt(ct, ct, &lrw->key)) != CRYPT_OK) {
93            return err;
94         }
95      }
96
97      /* xor prod */
98#ifdef LTC_FAST
99      for (x = 0; x < 16; x += sizeof(LTC_FAST_TYPE)) {
100           *((LTC_FAST_TYPE *)(ct + x)) = *((LTC_FAST_TYPE *)(ct + x)) ^ *((LTC_FAST_TYPE *)(prod + x));
101      }
102#else
103      for (x = 0; x < 16; x++) {
104         ct[x] = ct[x] ^ prod[x];
105      }
106#endif
107
108      /* move to next */
109      pt  += 16;
110      ct  += 16;
111      len -= 16;
112   }
113
114   return CRYPT_OK;
115}
116
117#endif
118/* $Source: /cvs/libtom/libtomcrypt/src/modes/lrw/lrw_process.c,v $ */
119/* $Revision: 1.10 $ */
120/* $Date: 2006/06/29 01:53:13 $ */
121