arc4simple.d

   1 /* Invisible Vector Library
   2  * coded by Ketmar // Invisible Vector <ketmar@ketmar.no-ip.org>
   3  * Understanding is not required. Only obedience.
   4  *
   5  * This program is free software: you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation, either version 3 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  17  */
  18 module iv.arc4simple /*is aliced*/;
  19 import iv.alice;
  20
  21
  22 // ///////////////////////////////////////////////////////////////////////// //
  23 struct ARC4Codec {
  24   ubyte[256] m; // permutation table
  25   ubyte x, y; // permutation indicies
  26
  27 nothrow @trusted @nogc:
  28   this (const(void)[] key, usize skipBytes=4096) { reinit(key, skipBytes); }
  29
  30   void reinit (const(void)[] key, usize skipBytes=4096) {
  31     assert(key.length > 0);
  32     auto keybytes = cast(const ubyte*)key.ptr;
  33     x = y = 0;
  34     foreach (immutable f; 0..256) m[f] = cast(ubyte)f;
  35     // create permutation table
  36     usize kidx = 0;
  37     ubyte c = 0;
  38     foreach (immutable f; 0..256) {
  39       auto kc = keybytes[kidx];
  40       auto a = m[f];
  41       c = (c+a+kc)&0xff;
  42       m[f] = m[c];
  43       m[c] = a;
  44       if (++kidx == key.length) kidx = 0;
  45     }
  46     // discard first bytes
  47     while (skipBytes--) {
  48       x = (x+1)&0xff;
  49       auto a = m[x];
  50       y = (y+a)&0xff;
  51       m[x] = m[y];
  52       m[y] = a;
  53     }
  54   }
  55
  56   void processBuffer(T) (T[] buf) {
  57     usize len = T.sizeof*buf.length;
  58     auto data = cast(ubyte*)buf.ptr;
  59     foreach (immutable _; 0..len) {
  60       x = (x+1)&0xff;
  61       auto a = m[x];
  62       y = (y+a)&0xff;
  63       auto bt = (m[x] = m[y]);
  64       m[y] = a;
  65       *data++ ^= m[(a+bt)&0xff];
  66     }
  67   }
  68 }
  69
  70
  71 // ///////////////////////////////////////////////////////////////////////// //
  72 version(arc4_tests) unittest {
  73   import std.algorithm;
  74   import std.stdio;
  75   writeln("unittest: arc4");
  76   enum ubyte[] sourceData = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];
  77   enum ubyte[] encodedData = [51,27,44,79,153,231,133,220,143,156,178,63,31,238,28,138];
  78   auto data = sourceData.dup;
  79   {
  80     auto a4 = ARC4Codec("asspole");
  81     a4.processBuffer(data);
  82     assert(equal(encodedData, data));
  83   }
  84   {
  85     auto a4 = ARC4Codec("asspole");
  86     a4.processBuffer(data);
  87     assert(equal(sourceData, data));
  88   }
  89 }