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, tomstdenis (at) gmail.com, http://libtomcrypt.com 10 */ 11 #include "tomcrypt.h" 12 13 /** 14 @file xcbc_done.c 15 XCBC Support, terminate the state 16 */ 17 18 #ifdef LTC_XCBC 19 20 /** Terminate the XCBC-MAC state 21 @param xcbc XCBC state to terminate 22 @param out [out] Destination for the MAC tag 23 @param outlen [in/out] Destination size and final tag size 24 Return CRYPT_OK on success 25 */ 26 int xcbc_done(xcbc_state *xcbc, unsigned char *out, unsigned long *outlen) 27 { 28 int err, x; 29 LTC_ARGCHK(xcbc != NULL); 30 LTC_ARGCHK(out != NULL); 31 32 /* check structure */ 33 if ((err = cipher_is_valid(xcbc->cipher)) != CRYPT_OK) { 34 return err; 35 } 36 37 if ((xcbc->blocksize > cipher_descriptor[xcbc->cipher].block_length) || (xcbc->blocksize < 0) || 38 (xcbc->buflen > xcbc->blocksize) || (xcbc->buflen < 0)) { 39 return CRYPT_INVALID_ARG; 40 } 41 42 /* which key do we use? */ 43 if (xcbc->buflen == xcbc->blocksize) { 44 /* k2 */ 45 for (x = 0; x < xcbc->blocksize; x++) { 46 xcbc->IV[x] ^= xcbc->K[1][x]; 47 } 48 } else { 49 xcbc->IV[xcbc->buflen] ^= 0x80; 50 /* k3 */ 51 for (x = 0; x < xcbc->blocksize; x++) { 52 xcbc->IV[x] ^= xcbc->K[2][x]; 53 } 54 } 55 56 /* encrypt */ 57 cipher_descriptor[xcbc->cipher].ecb_encrypt(xcbc->IV, xcbc->IV, &xcbc->key); 58 cipher_descriptor[xcbc->cipher].done(&xcbc->key); 59 60 /* extract tag */ 61 for (x = 0; x < xcbc->blocksize && (unsigned long)x < *outlen; x++) { 62 out[x] = xcbc->IV[x]; 63 } 64 *outlen = x; 65 66 #ifdef LTC_CLEAN_STACK 67 zeromem(xcbc, sizeof(*xcbc)); 68 #endif 69 return CRYPT_OK; 70 } 71 72 #endif 73 74 /* $Source: /cvs/libtom/libtomcrypt/src/mac/xcbc/xcbc_done.c,v $ */ 75 /* $Revision: 1.4 $ */ 76 /* $Date: 2006/11/07 03:23:46 $ */ 77 78
