Rearrange the file tree.

[u/mdw/catacomb] / symm / rc2.h

diff --git a/symm/rc2.h b/symm/rc2.h
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+/* -*-c-*-
+ *
+ * The RC2 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 RC2 block cipher -------------------------------------*
+ *
+ * RC2 was designed by Ron Rivest, and for a long time was a trade secret of
+ * RSA Data Security Inc.  Like RC4, it leaked out, and has now been
+ * described in RFC2268.  The RC2 key schedule is known to have some
+ * weaknesses, although I'm not aware of any major results against the cipher
+ * itself.  I'm also not aware of any legal problems with using the RC2
+ * cipher.
+ *
+ * The oddest feature in the cipher is the key schedule.  It expands the
+ * initial key material to 128 bytes, and then `brain-damages' it, according
+ * to a supplied `effective key-bits' parameter, before expanding the
+ * remaining key material back into the buffer.
+ *
+ * The key schedule allows second preimages to be computed trivially.
+ */
+
+#ifndef CATACOMB_RC2_H
+#define CATACOMB_RC2_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#include <stddef.h>
+
+#include <mLib/bits.h>
+
+/*----- Magical numbers ---------------------------------------------------*/
+
+#define RC2_BLKSZ 8
+#define RC2_KEYSZ 16
+#define RC2_CLASS (N, L, 64)
+
+extern const octet rc2_keysz[];
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef struct rc2_ctx {
+  uint16 k[64];
+} rc2_ctx;
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @rc2_braindamage@ --- *
+ *
+ * Arguments:  @rc2_ctx *k@ = pointer to context to initialize
+ *             @const void *buf@ = pointer to key material
+ *             @size_t sz@ = size of key material in bytes
+ *             @unsigned eb@ = desired effective key size, in bits
+ *
+ * Returns:    ---
+ *
+ * Use:                Initializes an RC2 expanded key, and braindamages it to the
+ *             requested effective key size.  This is here for compatibility
+ *             reasons.  You should be using @rc2_init@ in normal code,
+ *             which doesn't actually apply braindamage.
+ */
+
+extern void rc2_braindamage(rc2_ctx */*k*/, const void */*buf*/,
+                           size_t /*sz*/, unsigned /*eb*/);
+
+/* --- @rc2_init@ --- *
+ *
+ * Arguments:  @rc2_ctx *k@ = pointer to context to initialize
+ *             @const void *buf@ = pointer to key material
+ *             @size_t sz@ = size of key material in bytes
+ *
+ * Returns:    ---
+ *
+ * Use:                Initializes an RC2 expanded key.  The effective key size is
+ *             set to be equal to the real key size, in bits.
+ */
+
+extern void rc2_init(rc2_ctx */*k*/, const void */*buf*/, size_t /*sz*/);
+
+/* --- @rc2_eblk@, @rc2_dblk@ --- *
+ *
+ * Arguments:  @const rc2_ctx *k@ = pointer to RC2 context
+ *             @const uint32 s[2]@ = pointer to source block
+ *             @const uint32 d[2]@ = pointer to destination block
+ *
+ * Returns:    ---
+ *
+ * Use:                Low-level block encryption and decryption.
+ */
+
+extern void rc2_eblk(const rc2_ctx */*k*/,
+                    const uint32 */*s*/, uint32 */*dst*/);
+extern void rc2_dblk(const rc2_ctx */*k*/,
+                    const uint32 */*s*/, uint32 */*dst*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif