mdw@git.distorted.org.uk Git - catacomb/blob - symm/chacha-core.h

   1 /* -*-c-*-
   2  *
   3  * ChaCha core definitions
   4  *
   5  * (c) 2015 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Catacomb.
  11  *
  12  * Catacomb is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with Catacomb; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 #ifndef CATACOMB_CHACHA_CORE_H
  29 #define CATACOMB_CHACHA_CORE_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Header files ------------------------------------------------------*/
  36
  37 #include <mLib/bits.h>
  38 #include <mLib/macros.h>
  39
  40 #ifndef CATACOMB_CHACHA_H
  41 #  include "chacha.h"
  42 #endif
  43
  44 #ifndef CATACOMB_SALSA20_CORE_H
  45 #  include "salsa20-core.h"
  46 #endif
  47
  48 /*----- Magic constants ---------------------------------------------------*/
  49
  50 /* The magic ChaCha constants are the same as the Salsa20 ones.  For 256-bit
  51  * keys ...
  52  */
  53 #define CHACHA_A256 SALSA20_A256        /* e x p a */
  54 #define CHACHA_B256 SALSA20_B256        /* n d   3 */
  55 #define CHACHA_C256 SALSA20_C256        /* 2 - b y */
  56 #define CHACHA_D256 SALSA20_D256        /* t e   k */
  57
  58 /* ... and for 128-bit keys ... */
  59 #define CHACHA_A128 SALSA20_A128        /* e x p a */
  60 #define CHACHA_B128 SALSA20_B128        /* n d   1 */
  61 #define CHACHA_C128 SALSA20_C128        /* 6 - b y */
  62 #define CHACHA_D128 SALSA20_D128        /* t e   k */
  63
  64 /* ... and for 80-bit keys, for completeness's sake. */
  65 #define CHACHA_A80 SALSA20_A80          /* e x p a */
  66 #define CHACHA_B80 SALSA20_B80          /* n d   1 */
  67 #define CHACHA_C80 SALSA20_C80          /* 0 - b y */
  68 #define CHACHA_D80 SALSA20_D80          /* t e   k */
  69
  70 /*----- The ChaCha core function ------------------------------------------*/
  71
  72 /* The ChaCha quarter round.  Read from the matrix @y@ at indices @a@, @b@,
  73  * @c@, and @d@; and write to the corresponding elements of @z@.
  74  */
  75 #define CHACHA_QR(z, y, a, b, c, d) do {                                \
  76   (z)[a] = (y)[a] + (y)[b]; (z)[d] = ROL32((y)[d] ^ (z)[a], 16);        \
  77   (z)[c] = (y)[c] + (z)[d]; (z)[b] = ROL32((y)[b] ^ (z)[c], 12);        \
  78   (z)[a] = (z)[a] + (z)[b]; (z)[d] = ROL32((z)[d] ^ (z)[a],  8);        \
  79   (z)[c] = (z)[c] + (z)[d]; (z)[b] = ROL32((z)[b] ^ (z)[c],  7);        \
  80 } while (0)
  81
  82 /* The ChaCha double-round.  Read from matrix @y@, writing the result to
  83  * @z@.
  84  */
  85 #define CHACHA_DR(z, y) do {                                            \
  86   CHACHA_QR(z, y,  0,  4,  8, 12);                                      \
  87   CHACHA_QR(z, y,  1,  5,  9, 13);                                      \
  88   CHACHA_QR(z, y,  2,  6, 10, 14);                                      \
  89   CHACHA_QR(z, y,  3,  7, 11, 15);                                      \
  90   CHACHA_QR(z, z,  0,  5, 10, 15);                                      \
  91   CHACHA_QR(z, z,  1,  6, 11, 12);                                      \
  92   CHACHA_QR(z, z,  2,  7,  8, 13);                                      \
  93   CHACHA_QR(z, z,  3,  4,  9, 14);                                      \
  94 } while (0)
  95
  96 /* The ChaCha feedforward step, used at the end of the core function.  Here,
  97  * @y@ contains the original input matrix; @z@ contains the final one, and is
  98  * updated.  This is the same as Salsa20, only without the final permutation.
  99  */
 100 #define CHACHA_FFWD(z, y) do {                                          \
 101   int _i;                                                               \
 102   for (_i = 0; _i < 16; _i++) (z)[_i] += (y)[_i];                       \
 103 } while (0)
 104
 105 /* Various numbers of rounds, unrolled.  Read from @y@, and write to @z@. */
 106 #define CHACHA_4R(z, y)                                                 \
 107   do { CHACHA_DR(z, y); CHACHA_DR(z, z); } while (0)
 108 #define CHACHA_8R(z, y)                                                 \
 109   do { CHACHA_4R(z, y); CHACHA_4R(z, z); } while (0)
 110 #define CHACHA_12R(z, y)                                                \
 111   do { CHACHA_8R(z, y); CHACHA_4R(z, z); } while (0)
 112 #define CHACHA_20R(z, y)                                                \
 113   do { CHACHA_12R(z, y); CHACHA_8R(z, z); } while (0)
 114
 115 /* Apply @n@ (must be even) rounds, rolled.  (This seems to be faster,
 116  * probably because it fits in cache better).  Read from @y@, and write to
 117  * @z@.
 118  */
 119 #define CHACHA_nR(z, y, n) do {                                         \
 120   int _i;                                                               \
 121   CHACHA_DR(z, y);                                                      \
 122   for (_i = 0; _i < (n)/2 - 1; _i++) CHACHA_DR(z, z);                   \
 123 } while (0)
 124
 125 /* Step the counter in the Chacha state matrix @a@. */
 126 #define CHACHA_STEP(a)                                                  \
 127   do { (a)[12] = U32((a)[12] + 1); (a)[13] += !(a)[12]; } while (0)
 128
 129 /*----- Variants and naming -----------------------------------------------*/
 130
 131 /* Common numbers of rounds, for which we generate definitions. */
 132 #define CHACHA_VARS(_) _(8) _(12) _(20)
 133
 134 /*----- That's all, folks -------------------------------------------------*/
 135
 136 #ifdef __cplusplus
 137   }
 138 #endif
 139
 140 #endif