* des3.c: New file, implementing triple des.

Rev: src/nettle/des3.c:1.1

des3.c

+/* des3.h
+ *
+ * Triple DES cipher. Three key encrypt-decrypt-encrypt.
+ */
+
+/* nettle, low-level cryptographics library
+ *
+ * Copyright (C) 2001 Niels Mller
+ *  
+ * The nettle library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ * 
+ * The nettle library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the nettle library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#include "des.h"
+
+/* It's possible to make some more general pipe construction, like the
+ * lsh/src/cascade.c, but as in practice it's never used for anything
+ * like triple DES, it's not worth the effort. */
+
+/* On success, returns 1 and sets ctx->status to DES_OK (zero). On
+ * error, returns 0 and sets ctx->status accordingly. */
+int
+des3_set_key(struct des3_ctx *ctx, const uint8_t *key)
+{
+  unsigned i;
+  for (i = 0; i<3; i++, key += DES_KEY_SIZE)
+    if (!des_set_key(&ctx->des[i], key))
+      {
+	ctx->status = ctx->des[i].status;
+	return 0;
+      }
+  ctx->status = DES_OK;
+  return 1;
+}
+
+void
+des3_encrypt(struct des3_ctx *ctx,
+	     unsigned length, uint8_t *dst,
+	     const uint8_t *src)
+{
+  des_encrypt(&ctx->des[0],
+	      length, dst, src);
+  des_decrypt(&ctx->des[1],
+	      length, dst, dst);
+  des_encrypt(&ctx->des[2],
+	      length, dst, dst);
+}
+
+void
+des3_decrypt(struct des3_ctx *ctx,
+	    unsigned length, uint8_t *dst,
+	    const uint8_t *src)
+{
+  des_decrypt(&ctx->des[2],
+	      length, dst, src);
+  des_encrypt(&ctx->des[1],
+	      length, dst, dst);
+  des_decrypt(&ctx->des[0],
+	      length, dst, dst);
+}