Mercurial > dropbear
annotate src/modes/ctr/ctr_start.c @ 390:d8e44bef7917 libtomcrypt-dropbear
Replace // with /* */
author | Matt Johnston <matt@ucc.asn.au> |
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date | Thu, 11 Jan 2007 04:28:09 +0000 |
parents | d5faf4814ddb |
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280
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Re-import libtomcrypt 1.05 for cleaner propagating.
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
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2 * |
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3 * LibTomCrypt is a library that provides various cryptographic |
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4 * algorithms in a highly modular and flexible manner. |
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5 * |
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6 * The library is free for all purposes without any express |
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7 * guarantee it works. |
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8 * |
380 | 9 * Tom St Denis, [email protected], http://libtomcrypt.com |
280
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10 */ |
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11 #include "tomcrypt.h" |
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12 |
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13 /** |
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14 @file ctr_start.c |
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15 CTR implementation, start chain, Tom St Denis |
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16 */ |
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17 |
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18 |
380 | 19 #ifdef LTC_CTR_MODE |
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20 |
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21 /** |
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22 Initialize a CTR context |
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23 @param cipher The index of the cipher desired |
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24 @param IV The initial vector |
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25 @param key The secret key |
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26 @param keylen The length of the secret key (octets) |
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27 @param num_rounds Number of rounds in the cipher desired (0 for default) |
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28 @param ctr_mode The counter mode (CTR_COUNTER_LITTLE_ENDIAN or CTR_COUNTER_BIG_ENDIAN) |
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29 @param ctr The CTR state to initialize |
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30 @return CRYPT_OK if successful |
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31 */ |
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32 int ctr_start( int cipher, |
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33 const unsigned char *IV, |
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34 const unsigned char *key, int keylen, |
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35 int num_rounds, int ctr_mode, |
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36 symmetric_CTR *ctr) |
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37 { |
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38 int x, err; |
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39 |
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40 LTC_ARGCHK(IV != NULL); |
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41 LTC_ARGCHK(key != NULL); |
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42 LTC_ARGCHK(ctr != NULL); |
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43 |
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44 /* bad param? */ |
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45 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) { |
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46 return err; |
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47 } |
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48 |
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49 /* setup cipher */ |
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50 if ((err = cipher_descriptor[cipher].setup(key, keylen, num_rounds, &ctr->key)) != CRYPT_OK) { |
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51 return err; |
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52 } |
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53 |
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54 /* copy ctr */ |
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55 ctr->blocklen = cipher_descriptor[cipher].block_length; |
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56 ctr->cipher = cipher; |
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57 ctr->padlen = 0; |
380 | 58 ctr->mode = ctr_mode & 1; |
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59 for (x = 0; x < ctr->blocklen; x++) { |
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60 ctr->ctr[x] = IV[x]; |
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61 } |
380 | 62 |
63 if (ctr_mode & LTC_CTR_RFC3686) { | |
64 /* increment the IV as per RFC 3686 */ | |
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 | |
84 return cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key); | |
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85 } |
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86 |
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87 #endif |
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88 |
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89 /* $Source: /cvs/libtom/libtomcrypt/src/modes/ctr/ctr_start.c,v $ */ |
380 | 90 /* $Revision: 1.11 $ */ |
91 /* $Date: 2006/11/05 01:46:35 $ */ |