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comparison src/modes/cfb/cfb_decrypt.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 cfb_decrypt.c
15 CFB implementation, decrypt data, Tom St Denis
16 */
17
18 #ifdef CFB
19
20 /**
21 CFB decrypt
22 @param ct Ciphertext
23 @param pt [out] Plaintext
24 @param len Length of ciphertext (octets)
25 @param cfb CFB state
26 @return CRYPT_OK if successful
27 */
28 int cfb_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CFB *cfb)
29 {
30 int err;
31
32 LTC_ARGCHK(pt != NULL);
33 LTC_ARGCHK(ct != NULL);
34 LTC_ARGCHK(cfb != NULL);
35
36 if ((err = cipher_is_valid(cfb->cipher)) != CRYPT_OK) {
37 return err;
38 }
39
40 /* is blocklen/padlen valid? */
41 if (cfb->blocklen < 0 || cfb->blocklen > (int)sizeof(cfb->IV) ||
42 cfb->padlen < 0 || cfb->padlen > (int)sizeof(cfb->pad)) {
43 return CRYPT_INVALID_ARG;
44 }
45
46 while (len-- > 0) {
47 if (cfb->padlen == cfb->blocklen) {
48 cipher_descriptor[cfb->cipher].ecb_encrypt(cfb->pad, cfb->IV, &cfb->key);
49 cfb->padlen = 0;
50 }
51 cfb->pad[cfb->padlen] = *ct;
52 *pt = *ct ^ cfb->IV[cfb->padlen];
53 ++pt;
54 ++ct;
55 ++cfb->padlen;
56 }
57 return CRYPT_OK;
58 }
59
60 #endif
61