Mercurial > dropbear
annotate libtomcrypt/src/modes/cfb/cfb_decrypt.c @ 533:805ae74ec024
Encrypt in-place, avoid an extra malloc
author | Matt Johnston <matt@ucc.asn.au> |
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date | Sun, 01 Mar 2009 14:38:25 +0000 |
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children | f849a5ca2efc |
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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 * |
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9 * Tom St Denis, [email protected], http://libtomcrypt.com |
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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 cfb_decrypt.c |
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15 CFB implementation, decrypt data, Tom St Denis |
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16 */ |
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17 |
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18 #ifdef LTC_CFB_MODE |
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19 |
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20 /** |
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21 CFB decrypt |
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22 @param ct Ciphertext |
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23 @param pt [out] Plaintext |
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24 @param len Length of ciphertext (octets) |
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25 @param cfb CFB state |
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26 @return CRYPT_OK if successful |
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27 */ |
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28 int cfb_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CFB *cfb) |
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29 { |
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30 int err; |
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31 |
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32 LTC_ARGCHK(pt != NULL); |
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33 LTC_ARGCHK(ct != NULL); |
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34 LTC_ARGCHK(cfb != NULL); |
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35 |
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36 if ((err = cipher_is_valid(cfb->cipher)) != CRYPT_OK) { |
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37 return err; |
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38 } |
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39 |
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40 /* is blocklen/padlen valid? */ |
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41 if (cfb->blocklen < 0 || cfb->blocklen > (int)sizeof(cfb->IV) || |
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42 cfb->padlen < 0 || cfb->padlen > (int)sizeof(cfb->pad)) { |
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43 return CRYPT_INVALID_ARG; |
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44 } |
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45 |
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46 while (len-- > 0) { |
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47 if (cfb->padlen == cfb->blocklen) { |
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48 if ((err = cipher_descriptor[cfb->cipher].ecb_encrypt(cfb->pad, cfb->IV, &cfb->key)) != CRYPT_OK) { |
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49 return err; |
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50 } |
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51 cfb->padlen = 0; |
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52 } |
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53 cfb->pad[cfb->padlen] = *ct; |
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54 *pt = *ct ^ cfb->IV[cfb->padlen]; |
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55 ++pt; |
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56 ++ct; |
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57 ++(cfb->padlen); |
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58 } |
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59 return CRYPT_OK; |
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60 } |
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61 |
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62 #endif |
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63 |
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64 |
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65 /* $Source: /cvs/libtom/libtomcrypt/src/modes/cfb/cfb_decrypt.c,v $ */ |
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66 /* $Revision: 1.7 $ */ |
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67 /* $Date: 2006/11/26 01:45:14 $ */ |