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 ctr_encrypt.c
15  CTR implementation, encrypt data, Tom St Denis
16*/
17
18
19#ifdef LTC_CTR_MODE
20
21/**
22  CTR encrypt
23  @param pt     Plaintext
24  @param ct     [out] Ciphertext
25  @param len    Length of plaintext (octets)
26  @param ctr    CTR state
27  @return CRYPT_OK if successful
28*/
29int ctr_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CTR *ctr)
30{
31   int x, err;
32
33   LTC_ARGCHK(pt != NULL);
34   LTC_ARGCHK(ct != NULL);
35   LTC_ARGCHK(ctr != NULL);
36
37   if ((err = cipher_is_valid(ctr->cipher)) != CRYPT_OK) {
38       return err;
39   }
40
41   /* is blocklen/padlen valid? */
42   if (ctr->blocklen < 1 || ctr->blocklen > (int)sizeof(ctr->ctr) ||
43       ctr->padlen   < 0 || ctr->padlen   > (int)sizeof(ctr->pad)) {
44      return CRYPT_INVALID_ARG;
45   }
46
47#ifdef LTC_FAST
48   if (ctr->blocklen % sizeof(LTC_FAST_TYPE)) {
49      return CRYPT_INVALID_ARG;
50   }
51#endif
52
53   /* handle acceleration only if pad is empty, accelerator is present and length is >= a block size */
54   if ((ctr->padlen == ctr->blocklen) && cipher_descriptor[ctr->cipher].accel_ctr_encrypt != NULL && (len >= (unsigned long)ctr->blocklen)) {
55      if ((err = cipher_descriptor[ctr->cipher].accel_ctr_encrypt(pt, ct, len/ctr->blocklen, ctr->ctr, ctr->mode, &ctr->key)) != CRYPT_OK) {
56         return err;
57      }
58      len %= ctr->blocklen;
59   }
60
61   while (len) {
62      /* is the pad empty? */
63      if (ctr->padlen == ctr->blocklen) {
64         /* increment counter */
65         if (ctr->mode == CTR_COUNTER_LITTLE_ENDIAN) {
66            /* little-endian */
67            for (x = 0; x < ctr->blocklen; x++) {
68               ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
69               if (ctr->ctr[x] != (unsigned char)0) {
70                  break;
71               }
72            }
73         } else {
74            /* big-endian */
75            for (x = ctr->blocklen-1; x >= 0; x--) {
76               ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
77               if (ctr->ctr[x] != (unsigned char)0) {
78                  break;
79               }
80            }
81         }
82
83         /* encrypt it */
84         if ((err = cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key)) != CRYPT_OK) {
85            return err;
86         }
87         ctr->padlen = 0;
88      }
89#ifdef LTC_FAST
90      if (ctr->padlen == 0 && len >= (unsigned long)ctr->blocklen) {
91         for (x = 0; x < ctr->blocklen; x += sizeof(LTC_FAST_TYPE)) {
92            *((LTC_FAST_TYPE*)((unsigned char *)ct + x)) = *((LTC_FAST_TYPE*)((unsigned char *)pt + x)) ^
93                                                           *((LTC_FAST_TYPE*)((unsigned char *)ctr->pad + x));
94         }
95       pt         += ctr->blocklen;
96       ct         += ctr->blocklen;
97       len        -= ctr->blocklen;
98       ctr->padlen = ctr->blocklen;
99       continue;
100      }
101#endif
102      *ct++ = *pt++ ^ ctr->pad[ctr->padlen++];
103      --len;
104   }
105   return CRYPT_OK;
106}
107
108#endif
109
110/* $Source: /cvs/libtom/libtomcrypt/src/modes/ctr/ctr_encrypt.c,v $ */
111/* $Revision: 1.20 $ */
112/* $Date: 2006/11/21 00:18:23 $ */
113