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authorReimar Döffinger <Reimar.Doeffinger@gmx.de>2007-10-13 10:42:11 +0000
committerReimar Döffinger <Reimar.Doeffinger@gmx.de>2007-10-13 10:42:11 +0000
commit80b1c5a8580c84e45ee1304a6be21a629aca252f (patch)
tree1066cad9a4c035189335c8e58ed65b5b1061128a /libavutil/rc4.c
parent211dd1e81f3cbf3e4dd0cfad810bb4ba1362956d (diff)
downloadffmpeg-80b1c5a8580c84e45ee1304a6be21a629aca252f.tar.gz
Add RC4 encryption/decryption function
Originally committed as revision 10723 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavutil/rc4.c')
-rw-r--r--libavutil/rc4.c48
1 files changed, 48 insertions, 0 deletions
diff --git a/libavutil/rc4.c b/libavutil/rc4.c
new file mode 100644
index 0000000000..e59dac853e
--- /dev/null
+++ b/libavutil/rc4.c
@@ -0,0 +1,48 @@
+/*
+ * RC4 encryption/decryption/pseudo-random number generator
+ * Copyright (c) 2007 Reimar Doeffinger
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * loosely based on LibTomCrypt by Tom St Denis
+ */
+#include "common.h"
+#include "rc4.h"
+
+void ff_rc4_enc(const uint8_t *key, int keylen, uint8_t *data, int datalen) {
+ int i, j;
+ uint8_t x, y;
+ uint8_t state[256];
+ for (i = 0; i < 256; i++)
+ state[i] = i;
+ y = 0;
+ // j is i % keylen
+ for (j = 0, i = 0; i < 256; i++, j++) {
+ if (j == keylen) j = 0;
+ y += state[i] + key[j];
+ FFSWAP(uint8_t, state[i], state[y]);
+ }
+ // state initialized, now do the real encryption
+ x = 1; y = state[1];
+ while (datalen-- > 0) {
+ uint8_t sum = state[x] + state[y];
+ FFSWAP(uint8_t, state[x], state[y]);
+ *data++ ^= state[sum];
+ x++;
+ y += state[x];
+ }
+}