X-Git-Url: https://pd.if.org/git/?a=blobdiff_plain;ds=sidebyside;f=libtomcrypt%2Fsrc%2Fmodes%2Fctr%2Fctr_start.c;fp=libtomcrypt%2Fsrc%2Fmodes%2Fctr%2Fctr_start.c;h=039fdd6f574720a1310e82946ca68463e9f4a5bc;hb=66bc25938679f1d6a1d1200f329093d82a5e99b4;hp=0000000000000000000000000000000000000000;hpb=a52ee0733f420ca20224049260d6fc5cf7d8f621;p=zpackage

diff --git a/libtomcrypt/src/modes/ctr/ctr_start.c b/libtomcrypt/src/modes/ctr/ctr_start.c
new file mode 100644
index 0000000..039fdd6
--- /dev/null
+++ b/libtomcrypt/src/modes/ctr/ctr_start.c
@@ -0,0 +1,99 @@
+/* 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.
+ */
+#include "tomcrypt.h"
+
+/**
+   @file ctr_start.c
+   CTR implementation, start chain, Tom St Denis
+*/
+
+
+#ifdef LTC_CTR_MODE
+
+/**
+   Initialize a CTR context
+   @param cipher      The index of the cipher desired
+   @param IV          The initialization vector
+   @param key         The secret key
+   @param keylen      The length of the secret key (octets)
+   @param num_rounds  Number of rounds in the cipher desired (0 for default)
+   @param ctr_mode    The counter mode (CTR_COUNTER_LITTLE_ENDIAN or CTR_COUNTER_BIG_ENDIAN)
+   @param ctr         The CTR state to initialize
+   @return CRYPT_OK if successful
+*/
+int ctr_start(               int   cipher,
+              const unsigned char *IV,
+              const unsigned char *key,       int keylen,
+                             int  num_rounds, int ctr_mode,
+                   symmetric_CTR *ctr)
+{
+   int x, err;
+
+   LTC_ARGCHK(IV  != NULL);
+   LTC_ARGCHK(key != NULL);
+   LTC_ARGCHK(ctr != NULL);
+
+   /* bad param? */
+   if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* ctrlen == counter width */
+   ctr->ctrlen   = (ctr_mode & 255) ? (ctr_mode & 255) : cipher_descriptor[cipher].block_length;
+   if (ctr->ctrlen > cipher_descriptor[cipher].block_length) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   if ((ctr_mode & 0x1000) == CTR_COUNTER_BIG_ENDIAN) {
+      ctr->ctrlen = cipher_descriptor[cipher].block_length - ctr->ctrlen;
+   }
+
+   /* setup cipher */
+   if ((err = cipher_descriptor[cipher].setup(key, keylen, num_rounds, &ctr->key)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* copy ctr */
+   ctr->blocklen = cipher_descriptor[cipher].block_length;
+   ctr->cipher   = cipher;
+   ctr->padlen   = 0;
+   ctr->mode     = ctr_mode & 0x1000;
+   for (x = 0; x < ctr->blocklen; x++) {
+       ctr->ctr[x] = IV[x];
+   }
+
+   if (ctr_mode & LTC_CTR_RFC3686) {
+      /* increment the IV as per RFC 3686 */
+      if (ctr->mode == CTR_COUNTER_LITTLE_ENDIAN) {
+         /* little-endian */
+         for (x = 0; x < ctr->ctrlen; 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 >= ctr->ctrlen; x--) {
+             ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
+             if (ctr->ctr[x] != (unsigned char)0) {
+                break;
+             }
+         }
+      }
+   }
+
+   return cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key);
+}
+
+#endif
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */