--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ctr_encrypt.c	Mon May 31 18:25:41 2004 +0000
@@ -0,0 +1,64 @@
+/* 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 "mycrypt.h"
+
+#ifdef CTR
+
+int ctr_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CTR *ctr)
+{
+   int x, err;
+
+   _ARGCHK(pt != NULL);
+   _ARGCHK(ct != NULL);
+   _ARGCHK(ctr != NULL);
+
+   if ((err = cipher_is_valid(ctr->cipher)) != CRYPT_OK) {
+       return err;
+   }
+   
+   /* is blocklen/padlen valid? */
+   if (ctr->blocklen < 0 || ctr->blocklen > (int)sizeof(ctr->ctr) ||
+       ctr->padlen   < 0 || ctr->padlen   > (int)sizeof(ctr->pad)) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   while (len-- > 0) {
+      /* is the pad empty? */
+      if (ctr->padlen == ctr->blocklen) {
+         /* increment counter */
+         if (ctr->mode == 0) {
+            /* little-endian */
+            for (x = 0; x < ctr->blocklen; x++) {
+               ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
+               if (ctr->ctr[x] != (unsigned char)0) {
+                  break;
+               }
+            }
+         } else {
+            /* big-endian */
+            for (x = ctr->blocklen-1; x >= 0; x--) {
+               ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
+               if (ctr->ctr[x] != (unsigned char)0) {
+                  break;
+               }
+            }
+         }
+
+         /* encrypt it */
+         cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key);
+         ctr->padlen = 0;
+      }
+      *ct++ = *pt++ ^ ctr->pad[ctr->padlen++];
+   }
+   return CRYPT_OK;
+}
+
+#endif