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comparison src/modes/ctr/ctr_encrypt.c @ 192:9cc34777b479 libtomcrypt

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propagate from branch 'au.asn.ucc.matt.ltc-orig' (head 9ba8f01f44320e9cb9f19881105ae84f84a43ea9) to branch 'au.asn.ucc.matt.dropbear.ltc' (head dbf51c569bc34956ad948e4cc87a0eeb2170b768)
author Matt Johnston <matt@ucc.asn.au>
date Sun, 08 May 2005 06:36:47 +0000
parents 1c15b283127b
children 39d5d58461d6
comparison
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164:cd1143579f00 192:9cc34777b479
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, [email protected], http://libtomcrypt.org
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 CTR
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 */
29 int 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 < 0 || 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 cipher_descriptor[ctr->cipher].accel_ctr_encrypt(pt, ct, len/ctr->blocklen, ctr->ctr, ctr->mode, &ctr->key);
56 len %= ctr->blocklen;
57 }
58
59 while (len) {
60 /* is the pad empty? */
61 if (ctr->padlen == ctr->blocklen) {
62 /* increment counter */
63 if (ctr->mode == 0) {
64 /* little-endian */
65 for (x = 0; x < ctr->blocklen; x++) {
66 ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
67 if (ctr->ctr[x] != (unsigned char)0) {
68 break;
69 }
70 }
71 } else {
72 /* big-endian */
73 for (x = ctr->blocklen-1; x >= 0; x--) {
74 ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
75 if (ctr->ctr[x] != (unsigned char)0) {
76 break;
77 }
78 }
79 }
80
81 /* encrypt it */
82 cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key);
83 ctr->padlen = 0;
84 }
85 #ifdef LTC_FAST
86 if (ctr->padlen == 0 && len >= (unsigned long)ctr->blocklen) {
87 for (x = 0; x < ctr->blocklen; x += sizeof(LTC_FAST_TYPE)) {
88 *((LTC_FAST_TYPE*)((unsigned char *)ct + x)) = *((LTC_FAST_TYPE*)((unsigned char *)pt + x)) ^
89 *((LTC_FAST_TYPE*)((unsigned char *)ctr->pad + x));
90 }
91 pt += ctr->blocklen;
92 ct += ctr->blocklen;
93 len -= ctr->blocklen;
94 ctr->padlen = ctr->blocklen;
95 continue;
96 }
97 #endif
98 *ct++ = *pt++ ^ ctr->pad[ctr->padlen++];
99 --len;
100 }
101 return CRYPT_OK;
102 }
103
104 #endif