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213 lines
5.7 KiB
213 lines
5.7 KiB
#define LTC_SOURCE
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
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*/
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/**
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@file xtea.c
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Implementation of XTEA, Tom St Denis
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*/
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#include "tomcrypt.h"
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#ifdef XTEA
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const struct ltc_cipher_descriptor xtea_desc =
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{
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"xtea",
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1,
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16, 16, 8, 32,
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&xtea_setup,
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&xtea_ecb_encrypt,
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&xtea_ecb_decrypt,
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&xtea_test,
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&xtea_done,
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&xtea_keysize,
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NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
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};
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int xtea_setup(const unsigned char *key, int keylen, int num_rounds, symmetric_key *skey)
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{
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unsigned long x, sum, K[4];
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LTC_ARGCHK(key != NULL);
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LTC_ARGCHK(skey != NULL);
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/* check arguments */
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if (keylen != 16) {
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return CRYPT_INVALID_KEYSIZE;
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}
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if (num_rounds != 0 && num_rounds != 32) {
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return CRYPT_INVALID_ROUNDS;
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}
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/* load key */
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LOAD32L(K[0], key+0);
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LOAD32L(K[1], key+4);
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LOAD32L(K[2], key+8);
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LOAD32L(K[3], key+12);
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for (x = sum = 0; x < 32; x++) {
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skey->xtea.A[x] = (sum + K[sum&3]) & 0xFFFFFFFFUL;
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sum = (sum + 0x9E3779B9UL) & 0xFFFFFFFFUL;
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skey->xtea.B[x] = (sum + K[(sum>>11)&3]) & 0xFFFFFFFFUL;
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}
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#ifdef LTC_CLEAN_STACK
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zeromem(&K, sizeof(K));
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#endif
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return CRYPT_OK;
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}
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/**
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Encrypts a block of text with XTEA
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@param pt The input plaintext (8 bytes)
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@param ct The output ciphertext (8 bytes)
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@param skey The key as scheduled
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@return CRYPT_OK if successful
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*/
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int xtea_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *skey)
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{
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unsigned long y, z;
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int r;
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LTC_ARGCHK(pt != NULL);
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LTC_ARGCHK(ct != NULL);
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LTC_ARGCHK(skey != NULL);
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LOAD32L(y, &pt[0]);
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LOAD32L(z, &pt[4]);
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for (r = 0; r < 32; r += 4) {
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y = (y + ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r])) & 0xFFFFFFFFUL;
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z = (z + ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r])) & 0xFFFFFFFFUL;
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y = (y + ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r+1])) & 0xFFFFFFFFUL;
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z = (z + ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r+1])) & 0xFFFFFFFFUL;
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y = (y + ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r+2])) & 0xFFFFFFFFUL;
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z = (z + ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r+2])) & 0xFFFFFFFFUL;
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y = (y + ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r+3])) & 0xFFFFFFFFUL;
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z = (z + ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r+3])) & 0xFFFFFFFFUL;
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}
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STORE32L(y, &ct[0]);
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STORE32L(z, &ct[4]);
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return CRYPT_OK;
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}
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/**
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Decrypts a block of text with XTEA
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@param ct The input ciphertext (8 bytes)
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@param pt The output plaintext (8 bytes)
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@param skey The key as scheduled
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@return CRYPT_OK if successful
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*/
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int xtea_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *skey)
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{
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unsigned long y, z;
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int r;
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LTC_ARGCHK(pt != NULL);
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LTC_ARGCHK(ct != NULL);
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LTC_ARGCHK(skey != NULL);
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LOAD32L(y, &ct[0]);
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LOAD32L(z, &ct[4]);
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for (r = 31; r >= 0; r -= 4) {
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z = (z - ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r])) & 0xFFFFFFFFUL;
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y = (y - ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r])) & 0xFFFFFFFFUL;
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z = (z - ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r-1])) & 0xFFFFFFFFUL;
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y = (y - ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r-1])) & 0xFFFFFFFFUL;
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z = (z - ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r-2])) & 0xFFFFFFFFUL;
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y = (y - ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r-2])) & 0xFFFFFFFFUL;
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z = (z - ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r-3])) & 0xFFFFFFFFUL;
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y = (y - ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r-3])) & 0xFFFFFFFFUL;
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}
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STORE32L(y, &pt[0]);
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STORE32L(z, &pt[4]);
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return CRYPT_OK;
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}
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/**
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Performs a self-test of the XTEA block cipher
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@return CRYPT_OK if functional, CRYPT_NOP if self-test has been disabled
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*/
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int xtea_test(void)
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{
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#ifndef LTC_TEST
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return CRYPT_NOP;
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#else
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static const unsigned char key[16] =
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{ 0x78, 0x56, 0x34, 0x12, 0xf0, 0xcd, 0xcb, 0x9a,
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0x48, 0x37, 0x26, 0x15, 0xc0, 0xbf, 0xae, 0x9d };
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static const unsigned char pt[8] =
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{ 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 };
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static const unsigned char ct[8] =
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{ 0x75, 0xd7, 0xc5, 0xbf, 0xcf, 0x58, 0xc9, 0x3f };
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unsigned char tmp[2][8];
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symmetric_key skey;
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int err, y;
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if ((err = xtea_setup(key, 16, 0, &skey)) != CRYPT_OK) {
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return err;
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}
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xtea_ecb_encrypt(pt, tmp[0], &skey);
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xtea_ecb_decrypt(tmp[0], tmp[1], &skey);
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if (XMEMCMP(tmp[0], ct, 8) != 0 || XMEMCMP(tmp[1], pt, 8) != 0) {
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return CRYPT_FAIL_TESTVECTOR;
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}
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/* now see if we can encrypt all zero bytes 1000 times, decrypt and come back where we started */
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for (y = 0; y < 8; y++) tmp[0][y] = 0;
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for (y = 0; y < 1000; y++) xtea_ecb_encrypt(tmp[0], tmp[0], &skey);
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for (y = 0; y < 1000; y++) xtea_ecb_decrypt(tmp[0], tmp[0], &skey);
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for (y = 0; y < 8; y++) if (tmp[0][y] != 0) return CRYPT_FAIL_TESTVECTOR;
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return CRYPT_OK;
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#endif
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}
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/** Terminate the context
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@param skey The scheduled key
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*/
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void xtea_done(symmetric_key *skey)
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{
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}
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/**
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Gets suitable key size
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@param keysize [in/out] The length of the recommended key (in bytes). This function will store the suitable size back in this variable.
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@return CRYPT_OK if the input key size is acceptable.
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*/
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int xtea_keysize(int *keysize)
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{
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LTC_ARGCHK(keysize != NULL);
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if (*keysize < 16) {
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return CRYPT_INVALID_KEYSIZE;
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}
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*keysize = 16;
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return CRYPT_OK;
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}
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#endif
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/* $Source: /cvs/libtom/libtomcrypt/src/ciphers/xtea.c,v $ */
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/* $Revision: 1.12 $ */
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/* $Date: 2006/11/08 23:01:06 $ */
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