| /* arcfour.c --- The arcfour stream cipher |
| * Copyright (C) 2000-2003, 2005-2006, 2009-2020 Free Software Foundation, Inc. |
| * |
| * This file is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published |
| * by the Free Software Foundation; either version 2, or (at your |
| * option) any later version. |
| * |
| * This file 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 |
| * General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this file; if not, see <https://www.gnu.org/licenses/>. |
| * |
| */ |
| |
| /* Code from Libgcrypt adapted for gnulib by Simon Josefsson. */ |
| |
| /* |
| * For a description of the algorithm, see: |
| * Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996. |
| * ISBN 0-471-11709-9. Pages 397 ff. |
| */ |
| |
| #include <config.h> |
| |
| #include "arcfour.h" |
| |
| void |
| arcfour_stream (arcfour_context * context, const char *inbuf, char *outbuf, |
| size_t length) |
| { |
| uint8_t i = context->idx_i; |
| uint8_t j = context->idx_j; |
| char *sbox = context->sbox; |
| |
| for (; length > 0; length--) |
| { |
| char t; |
| |
| i++; |
| j += sbox[i]; |
| t = sbox[i]; |
| sbox[i] = sbox[j]; |
| sbox[j] = t; |
| *outbuf++ = (*inbuf++ |
| ^ sbox[(0U + sbox[i] + sbox[j]) % ARCFOUR_SBOX_SIZE]); |
| } |
| |
| context->idx_i = i; |
| context->idx_j = j; |
| } |
| |
| void |
| arcfour_setkey (arcfour_context * context, const char *key, size_t keylen) |
| { |
| size_t i, j, k; |
| char *sbox = context->sbox; |
| |
| context->idx_i = context->idx_j = 0; |
| for (i = 0; i < ARCFOUR_SBOX_SIZE; i++) |
| sbox[i] = i; |
| for (i = j = k = 0; i < ARCFOUR_SBOX_SIZE; i++) |
| { |
| char t; |
| j = (j + sbox[i] + key[k]) % ARCFOUR_SBOX_SIZE; |
| t = sbox[i]; |
| sbox[i] = sbox[j]; |
| sbox[j] = t; |
| if (++k == keylen) |
| k = 0; |
| } |
| } |