diff --git a/ChangeLog b/ChangeLog
index 56b65b49a..0fe3ea709 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,6 @@
 PolarSSL ChangeLog
 
-= Version 0.12.2 released on XXXXXXXX
+= Version 0.13.0 released on XXXXXXXX
 Features
    * Added option parsing for host and port selection to
      ssl_client2
@@ -15,6 +15,7 @@ Changes
      in a function to allow easy future expansion
    * Changed symmetric cipher functions to
      identical interface (returning int result values)
+   * Changed ARC4 to use seperate input/output buffer
 
 Bug fixes
    * Fixed bug resulting in failure to send the last
diff --git a/include/polarssl/arc4.h b/include/polarssl/arc4.h
index 76e7e0a3c..f6b9f138d 100644
--- a/include/polarssl/arc4.h
+++ b/include/polarssl/arc4.h
@@ -51,12 +51,14 @@ void arc4_setup( arc4_context *ctx, const unsigned char *key, int keylen );
  * \brief          ARC4 cipher function
  *
  * \param ctx      ARC4 context
- * \param buf      buffer to be processed
- * \param buflen   amount of data in buf
+ * \param length   length of the input data
+ * \param input    buffer holding the input data
+ * \param output   buffer for the output data
  *
  * \return         0
  */
-int arc4_crypt( arc4_context *ctx, unsigned char *buf, int buflen );
+int arc4_crypt( arc4_context *ctx, int length, const unsigned char *input,
+                unsigned char *output );
 
 /*
  * \brief          Checkup routine
diff --git a/library/arc4.c b/library/arc4.c
index 5e70311d7..b87053ec4 100644
--- a/library/arc4.c
+++ b/library/arc4.c
@@ -63,7 +63,8 @@ void arc4_setup( arc4_context *ctx, const unsigned char *key, int keylen )
 /*
  * ARC4 cipher function
  */
-int arc4_crypt( arc4_context *ctx, unsigned char *buf, int buflen )
+int arc4_crypt( arc4_context *ctx, int length, const unsigned char *input,
+                unsigned char *output )
 {
     int i, x, y, a, b;
     unsigned char *m;
@@ -72,7 +73,7 @@ int arc4_crypt( arc4_context *ctx, unsigned char *buf, int buflen )
     y = ctx->y;
     m = ctx->m;
 
-    for( i = 0; i < buflen; i++ )
+    for( i = 0; i < length; i++ )
     {
         x = ( x + 1 ) & 0xFF; a = m[x];
         y = ( y + a ) & 0xFF; b = m[y];
@@ -80,8 +81,8 @@ int arc4_crypt( arc4_context *ctx, unsigned char *buf, int buflen )
         m[x] = (unsigned char) b;
         m[y] = (unsigned char) a;
 
-        buf[i] = (unsigned char)
-            ( buf[i] ^ m[(unsigned char)( a + b )] );
+        output[i] = (unsigned char)
+            ( input[i] ^ m[(unsigned char)( a + b )] );
     }
 
     ctx->x = x;
@@ -127,7 +128,8 @@ static const unsigned char arc4_test_ct[3][8] =
 int arc4_self_test( int verbose )
 {
     int i;
-    unsigned char buf[8];
+    unsigned char ibuf[8];
+    unsigned char obuf[8];
     arc4_context ctx;
 
     for( i = 0; i < 3; i++ )
@@ -135,12 +137,12 @@ int arc4_self_test( int verbose )
         if( verbose != 0 )
             printf( "  ARC4 test #%d: ", i + 1 );
 
-        memcpy( buf, arc4_test_pt[i], 8 );
+        memcpy( ibuf, arc4_test_pt[i], 8 );
 
         arc4_setup( &ctx, (unsigned char *) arc4_test_key[i], 8 );
-        arc4_crypt( &ctx, buf, 8 );
+        arc4_crypt( &ctx, 8, ibuf, obuf );
 
-        if( memcmp( buf, arc4_test_ct[i], 8 ) != 0 )
+        if( memcmp( obuf, arc4_test_ct[i], 8 ) != 0 )
         {
             if( verbose != 0 )
                 printf( "failed\n" );
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 03975d29b..733551307 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -531,7 +531,8 @@ static int ssl_encrypt_buf( ssl_context *ssl )
                        ssl->out_msg, ssl->out_msglen );
 
         arc4_crypt( (arc4_context *) ssl->ctx_enc,
-                    ssl->out_msg, ssl->out_msglen );
+                    ssl->out_msglen, ssl->out_msg,
+                    ssl->out_msg );
 #else
         return( POLARSSL_ERR_SSL_FEATURE_UNAVAILABLE );
 #endif
@@ -618,7 +619,8 @@ static int ssl_decrypt_buf( ssl_context *ssl )
 #if defined(POLARSSL_ARC4_C)
         padlen = 0;
         arc4_crypt( (arc4_context *) ssl->ctx_dec,
-                    ssl->in_msg, ssl->in_msglen );
+                    ssl->in_msglen, ssl->in_msg,
+                    ssl->in_msg );
 #else
         return( POLARSSL_ERR_SSL_FEATURE_UNAVAILABLE );
 #endif
diff --git a/programs/test/benchmark.c b/programs/test/benchmark.c
index 5aeb4e32a..922c5eccd 100644
--- a/programs/test/benchmark.c
+++ b/programs/test/benchmark.c
@@ -169,11 +169,11 @@ int main( void )
 
     set_alarm( 1 );
     for( i = 1; ! alarmed; i++ )
-        arc4_crypt( &arc4, buf, BUFSIZE );
+        arc4_crypt( &arc4, BUFSIZE, buf, buf );
 
     tsc = hardclock();
     for( j = 0; j < 1024; j++ )
-        arc4_crypt( &arc4, buf, BUFSIZE );
+        arc4_crypt( &arc4, BUFSIZE, buf, buf );
 
     printf( "%9lu Kb/s,  %9lu cycles/byte\n", i * BUFSIZE / 1024,
                     ( hardclock() - tsc ) / ( j * BUFSIZE ) );
diff --git a/tests/suites/test_suite_arc4.function b/tests/suites/test_suite_arc4.function
index a7a533340..bc545a97f 100644
--- a/tests/suites/test_suite_arc4.function
+++ b/tests/suites/test_suite_arc4.function
@@ -7,22 +7,24 @@ arc4_crypt:hex_src_string:hex_key_string:hex_dst_string
 {
     unsigned char src_str[1000];
     unsigned char key_str[1000];
-    unsigned char dst_str[2000];
+    unsigned char dst_str[1000];
+    unsigned char dst_hexstr[2000];
     int src_len, key_len;
     arc4_context ctx;
 
     memset(src_str, 0x00, 1000);
     memset(key_str, 0x00, 1000);
-    memset(dst_str, 0x00, 2000);
+    memset(dst_str, 0x00, 1000);
+    memset(dst_hexstr, 0x00, 2000);
 
     src_len = unhexify( src_str, {hex_src_string} );
     key_len = unhexify( key_str, {hex_key_string} );
 
     arc4_setup(&ctx, key_str, key_len);
-    TEST_ASSERT( arc4_crypt(&ctx, src_str, src_len) == 0 );
-    hexify( dst_str, src_str, src_len );
+    TEST_ASSERT( arc4_crypt(&ctx, src_len, src_str, dst_str ) == 0 );
+    hexify( dst_hexstr, dst_str, src_len );
 
-    TEST_ASSERT( strcmp( (char *) dst_str, {hex_dst_string} ) == 0 );
+    TEST_ASSERT( strcmp( (char *) dst_hexstr, {hex_dst_string} ) == 0 );
 }
 END_CASE