git.distorted.org.uk Git - u/mdw/catacomb/blob - rc2.h

   1 /* -*-c-*-
   2  *
   3  * $Id: rc2.h,v 1.1 2000/06/17 11:54:34 mdw Exp $
   4  *
   5  * The RC2 block cipher
   6  *
   7  * (c) 2000 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: rc2.h,v $
  33  * Revision 1.1  2000/06/17 11:54:34  mdw
  34  * New cipher.
  35  *
  36  */
  37
  38 /*----- Notes on the RC2 block cipher -------------------------------------*
  39  *
  40  * RC2 was designed by Ron Rivest, and for a long time was a trade secret of
  41  * RSA Data Security Inc.  Like RC4, it leaked out, and has now been
  42  * described in RFC2268.  The RC2 key schedule is known to have some
  43  * weaknesses, although I'm not aware of any major results against the cipher
  44  * itself.  I'm also not aware of any legal problems with using the RC2
  45  * cipher.
  46  *
  47  * The oddest feature in the cipher is the key schedule.  It expands the
  48  * initial key material to 128 bytes, and then `brain-damages' it, according
  49  * to a supplied `effective key-bits' parameter, before expanding the
  50  * remaining key material back into the buffer.
  51  *
  52  * The key schedule allows second preimages to be computed trivially.
  53  */
  54
  55 #ifndef CATACOMB_RC2_H
  56 #define CATACOMB_RC2_H
  57
  58 #ifdef __cplusplus
  59   extern "C" {
  60 #endif
  61
  62 /*----- Header files ------------------------------------------------------*/
  63
  64 #include <stddef.h>
  65
  66 #include <mLib/bits.h>
  67
  68 /*----- Magical numbers ---------------------------------------------------*/
  69
  70 #define RC2_BLKSZ 8
  71 #define RC2_KEYSZ 16
  72 #define RC2_CLASS (N, L, 64)
  73
  74 extern const octet rc2_keysz[];
  75
  76 /*----- Data structures ---------------------------------------------------*/
  77
  78 typedef struct rc2_ctx {
  79   uint16 k[64];
  80 } rc2_ctx;
  81
  82 /*----- Functions provided ------------------------------------------------*/
  83
  84 /* --- @rc2_braindamage@ --- *
  85  *
  86  * Arguments:   @rc2_ctx *k@ = pointer to context to initialize
  87  *              @const void *buf@ = pointer to key material
  88  *              @size_t sz@ = size of key material in bytes
  89  *              @unsigned eb@ = desired effective key size, in bits
  90  *
  91  * Returns:     ---
  92  *
  93  * Use:         Initializes an RC2 expanded key, and braindamages it to the
  94  *              requested effective key size.  This is here for compatibility
  95  *              reasons.  You should be using @rc2_init@ in normal code,
  96  *              which doesn't actually apply braindamage.
  97  */
  98
  99 extern void rc2_braindamage(rc2_ctx */*k*/, const void */*buf*/,
 100                             size_t /*sz*/, unsigned /*eb*/);
 101
 102 /* --- @rc2_init@ --- *
 103  *
 104  * Arguments:   @rc2_ctx *k@ = pointer to context to initialize
 105  *              @const void *buf@ = pointer to key material
 106  *              @size_t sz@ = size of key material in bytes
 107  *
 108  * Returns:     ---
 109  *
 110  * Use:         Initializes an RC2 expanded key.  The effective key size is
 111  *              set to be equal to the real key size, in bits.
 112  */
 113
 114 extern void rc2_init(rc2_ctx */*k*/, const void */*buf*/, size_t /*sz*/);
 115
 116 /* --- @rc2_eblk@, @rc2_dblk@ --- *
 117  *
 118  * Arguments:   @const rc2_ctx *k@ = pointer to RC2 context
 119  *              @const uint32 s[2]@ = pointer to source block
 120  *              @const uint32 d[2]@ = pointer to destination block
 121  *
 122  * Returns:     ---
 123  *
 124  * Use:         Low-level block encryption and decryption.
 125  */
 126
 127 extern void rc2_eblk(const rc2_ctx */*k*/,
 128                      const uint32 */*s*/, uint32 */*dst*/);
 129 extern void rc2_dblk(const rc2_ctx */*k*/,
 130                      const uint32 */*s*/, uint32 */*dst*/);
 131
 132 /*----- That's all, folks -------------------------------------------------*/
 133
 134 #ifdef __cplusplus
 135   }
 136 #endif
 137
 138 #endif