--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/modes/cbc/cbc_decrypt.c	Fri May 06 13:23:02 2005 +0000
@@ -0,0 +1,91 @@
+/* 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
+ */
+#include "tomcrypt.h"
+
+/**
+   @file cbc_decrypt.c
+   CBC implementation, encrypt block, Tom St Denis
+*/
+
+
+#ifdef CBC
+
+/**
+  CBC decrypt
+  @param ct     Ciphertext
+  @param pt     [out] Plaintext
+  @param len    The number of bytes to process (must be multiple of block length)
+  @param cbc    CBC state
+  @return CRYPT_OK if successful
+*/
+int cbc_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CBC *cbc)
+{
+   int x, err;
+   unsigned char tmp[16];
+#ifdef LTC_FAST
+   LTC_FAST_TYPE tmpy;
+#else
+   unsigned char tmpy;
+#endif         
+
+   LTC_ARGCHK(pt  != NULL);
+   LTC_ARGCHK(ct  != NULL);
+   LTC_ARGCHK(cbc != NULL);
+
+   if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) {
+       return err;
+   }
+   
+   /* is blocklen valid? */
+   if (cbc->blocklen < 0 || cbc->blocklen > (int)sizeof(cbc->IV)) {
+      return CRYPT_INVALID_ARG;
+   }    
+
+   if (len % cbc->blocklen) {
+      return CRYPT_INVALID_ARG;
+   }
+#ifdef LTC_FAST
+   if (len % sizeof(LTC_FAST_TYPE)) {   
+      return CRYPT_INVALID_ARG;
+   }
+#endif
+   
+   if (cipher_descriptor[cbc->cipher].accel_cbc_decrypt != NULL) {
+      cipher_descriptor[cbc->cipher].accel_cbc_decrypt(ct, pt, len / cbc->blocklen, cbc->IV, &cbc->key);
+   } else {
+      while (len) {
+         /* decrypt */
+         cipher_descriptor[cbc->cipher].ecb_decrypt(ct, tmp, &cbc->key);
+
+         /* xor IV against plaintext */
+         #if defined(LTC_FAST)
+	     for (x = 0; x < cbc->blocklen; x += sizeof(LTC_FAST_TYPE)) {
+	         tmpy = *((LTC_FAST_TYPE*)((unsigned char *)cbc->IV + x)) ^ *((LTC_FAST_TYPE*)((unsigned char *)tmp + x));
+		 *((LTC_FAST_TYPE*)((unsigned char *)cbc->IV + x)) = *((LTC_FAST_TYPE*)((unsigned char *)ct + x));
+		 *((LTC_FAST_TYPE*)((unsigned char *)pt + x)) = tmpy;
+	     }
+	 #else 
+            for (x = 0; x < cbc->blocklen; x++) {
+               tmpy       = tmp[x] ^ cbc->IV[x];
+               cbc->IV[x] = ct[x];
+               pt[x]      = tmpy;
+            }
+	 #endif
+       
+         ct  += cbc->blocklen;
+         pt  += cbc->blocklen;
+         len -= cbc->blocklen;
+      }
+   }
+   return CRYPT_OK;
+}
+
+#endif