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
12/**
13   @file ocb_encrypt.c
14   OCB implementation, encrypt data, by Tom St Denis
15*/
16#include "tomcrypt.h"
17
18#ifdef OCB_MODE
19
20/**
21   Encrypt a block of data with OCB.
22   @param ocb     The OCB state
23   @param pt      The plaintext (length of the block size of the block cipher)
24   @param ct      [out] The ciphertext (same size as the pt)
25   @return CRYPT_OK if successful
26*/
27int ocb_encrypt(ocb_state *ocb, const unsigned char *pt, unsigned char *ct)
28{
29   unsigned char Z[MAXBLOCKSIZE], tmp[MAXBLOCKSIZE];
30   int err, x;
31
32   LTC_ARGCHK(ocb != NULL);
33   LTC_ARGCHK(pt  != NULL);
34   LTC_ARGCHK(ct  != NULL);
35   if ((err = cipher_is_valid(ocb->cipher)) != CRYPT_OK) {
36      return err;
37   }
38   if (ocb->block_len != cipher_descriptor[ocb->cipher].block_length) {
39      return CRYPT_INVALID_ARG;
40   }
41
42   /* compute checksum */
43   for (x = 0; x < ocb->block_len; x++) {
44       ocb->checksum[x] ^= pt[x];
45   }
46
47   /* Get Z[i] value */
48   ocb_shift_xor(ocb, Z);
49
50   /* xor pt in, encrypt, xor Z out */
51   for (x = 0; x < ocb->block_len; x++) {
52       tmp[x] = pt[x] ^ Z[x];
53   }
54   if ((err = cipher_descriptor[ocb->cipher].ecb_encrypt(tmp, ct, &ocb->key)) != CRYPT_OK) {
55      return err;
56   }
57   for (x = 0; x < ocb->block_len; x++) {
58       ct[x] ^= Z[x];
59   }
60
61#ifdef LTC_CLEAN_STACK
62   zeromem(Z, sizeof(Z));
63   zeromem(tmp, sizeof(tmp));
64#endif
65   return CRYPT_OK;
66}
67
68#endif
69
70/* $Source: /cvs/libtom/libtomcrypt/src/encauth/ocb/ocb_encrypt.c,v $ */
71/* $Revision: 1.5 $ */
72/* $Date: 2006/03/31 14:15:35 $ */
73