--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/ciphers/xtea.c	Fri Mar 10 06:31:29 2006 +0000
@@ -0,0 +1,207 @@
+/* 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, [email protected], http://libtomcrypt.org
+ */
+
+/**
+  @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
+};
+
+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
+*/
+void 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]);
+}
+
+/**
+  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 
+*/
+void 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]);
+}
+
+/**
+  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 (memcmp(tmp[0], ct, 8) != 0 || memcmp(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: 1.7 $ */
+/* $Date: 2005/05/05 14:35:58 $ */