disorder-choose now uses an arcfour keystream as its RNG instead of

[disorder] / lib / arcfour.c

diff --git a/lib/arcfour.c b/lib/arcfour.c
new file mode 100644 (file)
index 0000000..42aaf2b
--- /dev/null
+++ b/lib/arcfour.c
@@ -0,0 +1,76 @@
+/* arcfour.c --- The arcfour stream cipher
+ * Copyright (C) 2000, 2001, 2002, 2003, 2005, 2006 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ */
+
+/* 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 "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;
+    }
+}