added libtomcrypt-1.00

2004-12-30 23:55:53 +00:00
parent 1c1822d510
commit bfc2f5b078
257 changed files with 12657 additions and 5352 deletions
@@ -0,0 +1,69 @@
+/* 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@iahu.ca, http://libtomcrypt.org
+ */
+#include "tomcrypt.h"
+
+/**
+   @file cbc_decrypt.c
+   CBC implementation, decrypt block, Tom St Denis
+*/
+
+#ifdef CBC
+
+/**
+   CBC decrypt
+   @param ct      Ciphertext
+   @param pt      [out] Plaintext
+   @param cbc     CBC state
+   @return CRYPT_OK if successful
+*/
+int cbc_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_CBC *cbc)
+{
+   int x, err;
+   unsigned char tmp[MAXBLOCKSIZE], tmp2[MAXBLOCKSIZE];
+
+   LTC_ARGCHK(pt != NULL);
+   LTC_ARGCHK(ct != NULL);
+   LTC_ARGCHK(cbc != NULL);
+
+   /* decrypt the block from ct into tmp */
+   if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) {
+       return err;
+   }
+   LTC_ARGCHK(cipher_descriptor[cbc->cipher].ecb_decrypt != NULL);
+      
+   /* is blocklen valid? */
+   if (cbc->blocklen < 0 || cbc->blocklen > (int)sizeof(cbc->IV)) {
+      return CRYPT_INVALID_ARG;
+   } 
+
+   /* decrypt and xor IV against the plaintext of the previous step */
+   cipher_descriptor[cbc->cipher].ecb_decrypt(ct, tmp, &cbc->key);
+   for (x = 0; x < cbc->blocklen; x++) { 
+       /* copy CT in case ct == pt */
+       tmp2[x] = ct[x]; 
+
+       /* actually decrypt the byte */
+       pt[x] = tmp[x] ^ cbc->IV[x]; 
+   }
+
+   /* replace IV with this current ciphertext */ 
+   for (x = 0; x < cbc->blocklen; x++) {
+       cbc->IV[x] = tmp2[x];
+   }
+   #ifdef LTC_CLEAN_STACK
+      zeromem(tmp, sizeof(tmp));
+      zeromem(tmp2, sizeof(tmp2));
+   #endif
+   return CRYPT_OK;
+}
+
+#endif
+