X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/ba6e6b64033b1f9de49feccb5c9cd438354481f7..0f00dc4c8eb47e67bc0f148c2dd109f73a451e0a:/symm/skipjack.h

diff --git a/symm/skipjack.h b/symm/skipjack.h
new file mode 100644
index 0000000..ab43709
--- /dev/null
+++ b/symm/skipjack.h
@@ -0,0 +1,110 @@
+/* -*-c-*-
+ *
+ * The Skipjack block cipher
+ *
+ * (c) 2000 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * Catacomb 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 Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Notes on the Skipjack block cipher --------------------------------*
+ *
+ * Skipjack was designed by the NSA, as a type II algorithm to be used in the
+ * Clipper system.  It was initially classified, so that it couldn't be used
+ * without the key escrow feature, though a team of `respectable'
+ * cryptographers, including Dorothy Denning, had a quick look at it and
+ * pronounced it `good', as if this was meant to be convincing.  It is
+ * apparently a particular parameterization of a family which includes type I
+ * algorithms.  Since declassification, Biham has discovered a miss-in-the-
+ * middle attack which breaks Skipjack with 31 rounds faster than brute
+ * force.
+ *
+ * This implementation is provided for interest's sake, and possibly for
+ * interoperability, rather than as a good cipher to use.
+ */
+
+#ifndef CATACOMB_SKIPJACK_H
+#define CATACOMB_SKIPJACK_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <stddef.h>
+
+#include <mLib/bits.h>
+
+/*----- Magical numbers ---------------------------------------------------*/
+
+#define SKIPJACK_BLKSZ 8
+#define SKIPJACK_KEYSZ 10
+#define SKIPJACK_CLASS (N, B, 64)
+
+extern const octet skipjack_keysz[];
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef struct skipjack_ctx {
+  uint32 ka, kb, kc, kd, ke;
+} skipjack_ctx;
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @skipjack_init@ --- *
+ *
+ * Arguments:	@skipjack_ctx *k@ = pointer to key block
+ *		@const void *buf@ = pointer to key buffer
+ *		@size_t sz@ = size of key material
+ *
+ * Returns:	---
+ *
+ * Use:		Initializes a Skipjack key buffer.  The key buffer must be
+ *		exactly 10 bytes long.
+ */
+
+extern void skipjack_init(skipjack_ctx */*k*/,
+			  const void */*buf*/, size_t /*sz*/);
+
+/* --- @skipjack_eblk@, @skipjack_dblk@ --- *
+ *
+ * Arguments:	@const skipjack_ctx *k@ = pointer to key block
+ *		@const uint32 s[2]@ = pointer to source block
+ *		@uint32 d[2]@ = pointer to skipjacktination block
+ *
+ * Returns:	---
+ *
+ * Use:		Low-level block encryption and decryption.
+ */
+
+extern void skipjack_eblk(const skipjack_ctx */*k*/,
+			  const uint32 */*s*/, uint32 */*d*/);
+extern void skipjack_dblk(const skipjack_ctx */*k*/,
+			  const uint32 */*s*/, uint32 */*d*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif