Mercurial > dropbear

annotate libtomcrypt/src/modes/cfb/cfb_encrypt.c @ 994:5c5ade336926

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Prefer stronger algorithms in algorithm negotiation. Prefer diffie-hellman-group14-sha1 (2048 bit) over diffie-hellman-group1-sha1 (1024 bit). Due to meet-in-the-middle attacks the effective key length of three key 3DES is 112 bits. AES is stronger and faster then 3DES. Prefer to delay the start of compression until after authentication has completed. This avoids exposing compression code to attacks from unauthenticated users. (github pull request #9)
author Fedor Brunner <fedor.brunner@azet.sk>
date Fri, 23 Jan 2015 23:00:25 +0800
parents 0cbe8f6dbf9e
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_encrypt.c
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15 CFB implementation, encrypt 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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20 /**
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21 CFB encrypt
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22 @param pt Plaintext
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23 @param ct [out] Ciphertext
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24 @param len Length of plaintext (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_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CFB *cfb)
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29 {
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30 int err;
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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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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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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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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 = *pt ^ cfb->IV[cfb->padlen]);
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54 ++pt;
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55 ++ct;
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56 ++(cfb->padlen);
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57 }
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58 return CRYPT_OK;
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59 }
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61 #endif
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63 /* $Source: /cvs/libtom/libtomcrypt/src/modes/cfb/cfb_encrypt.c,v $ */
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64 /* $Revision: 1.7 $ */
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65 /* $Date: 2006/11/26 01:45:14 $ */