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[u/mdw/catacomb] / symm / idea.h

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+/* -*-c-*-
+ *
+ * Implementation of the IDEA cipher
+ *
+ * (c) 1999 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 IDEA block cipher ------------------------------------*
+ *
+ * IDEA was invented by James Massey and Xuejia Lai.  The fundamental idea
+ * underlying the cipher is combining incompatible group operations.  The
+ * algorithm's main claim to fame is that it is the symmetric cipher in PGP
+ * version 2.
+ *
+ * The IDEA algorithm is allegedly patented by Ascom Tech A.G., even in the
+ * UK and Europe.  Ascom are willing to grant licences for use in software
+ * which forbids commercial use, but this is not compatible with Free
+ * Software Foundation ideology.  The author recommends against the use of
+ * the IDEA cipher entirely.  Blowfish is conceptually simpler, appears more
+ * concervative, offers a larger keyspace, runs faster, and is in the public
+ * domain.
+ */
+
+#ifndef CATACOMB_IDEA_H
+#define CATACOMB_IDEA_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <stddef.h>
+
+#include <mLib/bits.h>
+
+/*----- Magical numbers ---------------------------------------------------*/
+
+#define IDEA_BLKSZ 8
+#define IDEA_KEYSZ 16
+#define IDEA_CLASS (N, B, 64)
+
+extern const octet idea_keysz[];
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef struct idea_ctx {
+  uint16 e[52];
+  uint16 d[52];
+} idea_ctx;
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @idea_init@ --- *
+ *
+ * Arguments:  @idea_ctx *k@ = pointer to key block
+ *             @const void *buf@ = pointer to key buffer
+ *             @size_t sz@ = size of key material
+ *
+ * Returns:    ---
+ *
+ * Use:                Initializes an IDEA key buffer.  The buffer must be exactly
+ *             16 bytes in size, because IDEA is only defined with a key
+ *             size of 128 bits.
+ */
+
+extern void idea_init(idea_ctx */*k*/, const void */*buf*/, size_t /*sz*/);
+
+/* --- @idea_eblk@, @idea_dblk@ --- *
+ *
+ * Arguments:  @const idea_ctx *k@ = pointer to a key block
+ *             @const uint32 s[2]@ = pointer to source block
+ *             @uint32 d[2]@ = pointer to destination block
+ *
+ * Returns:    ---
+ *
+ * Use:                Low-level block encryption and decryption.
+ */
+
+extern void idea_eblk(const idea_ctx */*k*/,
+                     const uint32 */*s*/, uint32 */*d*/);
+extern void idea_dblk(const idea_ctx */*k*/,
+                     const uint32 */*s*/, uint32 */*d*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif