- Fixed cipher interface for encrypt/decrypt functions

diff --git a/include/polarssl/arc4.h b/include/polarssl/arc4.h
index 20f142a..76e7e0a 100644
--- a/include/polarssl/arc4.h
+++ b/include/polarssl/arc4.h
@@ -53,8 +53,10 @@
  * \param ctx      ARC4 context
  * \param buf      buffer to be processed
  * \param buflen   amount of data in buf
+ *
+ * \return         0
  */
-void arc4_crypt( arc4_context *ctx, unsigned char *buf, int buflen );
+int arc4_crypt( arc4_context *ctx, unsigned char *buf, int buflen );
 
 /*
  * \brief          Checkup routine