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