speed-up AES decryption (around factor 2)

get rid of as3crypto.swc (avoid ByteArray creation, and a bunch of copy)

README.md

@@ -168,7 +168,6 @@ swfobject.embedSWF('StrobeMediaPlayback.swf', 'player', 640, 360, '10.2', null,
 ## License
 
   - [MPL 2.0](https://github.com/mangui/flashls/blob/master/LICENSE)
-  - [as3crypto.swc](https://github.com/timkurvers/as3-crypto) is governed by a `BSD` license
 
 ## Donation
 

build/build.sh

@@ -3,15 +3,13 @@ FLEXPATH=../../flex_sdk_4.6
 #FLEXPATH=../../../apache_flex_sdk
 #FLEXPATH=../../../AIRSDK_Compiler
 
-OPT_DEBUG="-library-path+=../lib/as3crypto.swc \
-    -use-network=false \
+OPT_DEBUG="-use-network=false \
     -optimize=true \
     -incremental=true \
     -static-link-runtime-shared-libraries=true \
     -define=CONFIG::LOGGING,true"
 
-OPT_RELEASE="-library-path+=../lib/as3crypto.swc \
-    -use-network=false \
+OPT_RELEASE="-use-network=false \
     -optimize=true \
     -incremental=true \
     -static-link-runtime-shared-libraries=true \

src/org/mangui/hls/demux/TSDemuxer.as

@@ -1,7 +1,5 @@
 package org.mangui.hls.demux {
-    import org.mangui.hls.HLSSettings;
-
-    import com.hurlant.util.Hex;
+    import org.mangui.hls.utils.Hex;
 
   	import org.mangui.hls.flv.FLVTag;
     import org.mangui.hls.HLSAudioTrack;
@@ -14,6 +12,7 @@ package org.mangui.hls.demux {
 
     CONFIG::LOGGING {
     import org.mangui.hls.utils.Log;
+    import org.mangui.hls.HLSSettings;
     }
 
     /** Representation of an MPEG transport stream. **/

src/org/mangui/hls/playlist/Manifest.as

@@ -1,5 +1,5 @@
 package org.mangui.hls.playlist {
-    import com.hurlant.util.Hex;
+    import org.mangui.hls.utils.Hex;
 
     import flash.events.*;
     import flash.net.*;

src/org/mangui/hls/stream/FragmentLoader.as

@@ -1,5 +1,4 @@
 package org.mangui.hls.stream {
-    import com.hurlant.util.Hex;
 
     import flash.events.*;
     import flash.net.*;
@@ -18,6 +17,7 @@ package org.mangui.hls.stream {
 
     CONFIG::LOGGING {
     import org.mangui.hls.utils.Log;
+    import org.mangui.hls.utils.Hex;
     }
 
     /** Class that fetches fragments. **/

src/org/mangui/hls/utils/AES.as

@@ -1,23 +1,18 @@
 package org.mangui.hls.utils {
-    import com.hurlant.crypto.symmetric.CBCMode;
-    import com.hurlant.crypto.symmetric.ICipher;
-    import com.hurlant.crypto.symmetric.IPad;
-    import com.hurlant.crypto.symmetric.IVMode;
-    import com.hurlant.crypto.symmetric.NullPad;
-    import com.hurlant.crypto.symmetric.PKCS5;
-
     import flash.utils.ByteArray;
     import flash.utils.Timer;
     import flash.events.Event;
     import flash.events.TimerEvent;
 
     /**
-     * Contains Utility functions for Decryption
+     * Contains Utility functions for AES-128 CBC Decryption
      */
     public class AES {
         private var _key : FastAESKey;
-        private var _mode : ICipher;
-        private var _iv : ByteArray;
+        private var iv0 : uint;
+        private var iv1 : uint;
+        private var iv2 : uint;
+        private var iv3 : uint;
         /* callback function upon decrypt progress */
         private var _progress : Function;
         /* callback function upon decrypt complete */
@@ -36,15 +31,12 @@ package org.mangui.hls.utils {
         private var _data_complete : Boolean;
 
         public function AES(key : ByteArray, iv : ByteArray, notifyprogress : Function, notifycomplete : Function) {
-            var pad : IPad = new PKCS5;
             _key = new FastAESKey(key);
-            _mode = new CBCMode(_key, pad);
-            pad.setBlockSize(_mode.getBlockSize());
-            _iv = iv;
-            if (_mode is IVMode) {
-                var ivmode : IVMode = _mode as IVMode;
-                ivmode.IV = iv;
-            }
+            iv.position = 0;
+            iv0 = iv.readUnsignedInt();
+            iv1 = iv.readUnsignedInt();
+            iv2 = iv.readUnsignedInt();
+            iv3 = iv.readUnsignedInt();
             _data = new ByteArray();
             _data_complete = false;
             _progress = notifyprogress;
@@ -61,7 +53,7 @@ package org.mangui.hls.utils {
             // }
             _data.position = _write_position;
             _data.writeBytes(data);
-            _write_position+= data.length;
+            _write_position += data.length;
             _timer.start();
         }
 
@@ -91,74 +83,94 @@ package org.mangui.hls.utils {
         /** decrypt a small chunk of packets each time to avoid blocking **/
         private function _decryptData() : void {
             _data.position = _read_position;
+            var decryptdata : ByteArray;
             if (_data.bytesAvailable) {
-                var dumpByteArray : ByteArray = new ByteArray();
-                var newIv : ByteArray;
-                var pad : IPad;
                 if (_data.bytesAvailable <= CHUNK_SIZE) {
                     if (_data_complete) {
                         // CONFIG::LOGGING {
                         // Log.info("data complete, last chunk");
                         // }
-                        pad = new PKCS5;
                         _read_position += _data.bytesAvailable;
-                        _data.readBytes(dumpByteArray, 0, _data.bytesAvailable);
+                        decryptdata = _decryptCBC(_data, _data.bytesAvailable);
+                        unpad(decryptdata);
                     } else {
+                        // data not complete, and available data less than chunk size, stop timer and return
                         // CONFIG::LOGGING {
                         // Log.info("data not complete, stop timer");
                         // }
-                        // data not complete, and available data less than chunk size, stop timer and return
                         _timer.stop();
                         return;
                     }
                 } else {
-                    // bytesAvailable > CHUNK_SIZE
-                    // CONFIG::LOGGING {
-                    // Log.info("process chunk");
-                    // }
-                    pad = new NullPad;
                     _read_position += CHUNK_SIZE;
-                    _data.readBytes(dumpByteArray, 0, CHUNK_SIZE);
-                    // Save new IV from ciphertext
-                    newIv = new ByteArray();
-                    dumpByteArray.position = (CHUNK_SIZE - 16);
-                    dumpByteArray.readBytes(newIv, 0, 16);
-                }
-                dumpByteArray.position = 0;
-                // CONFIG::LOGGING {
-                // Log.info("before decrypt");
-                // }
-                _mode = new CBCMode(_key, pad);
-                pad.setBlockSize(_mode.getBlockSize());
-                (_mode as IVMode).IV = _iv;
-                _mode.decrypt(dumpByteArray);
-                // CONFIG::LOGGING {
-                // Log.info("after decrypt");
-                // }
-                _progress(dumpByteArray);
-                // switch IV to new one in case more bytes are available
-                if (newIv) {
-                    _iv = newIv;
+                    decryptdata = _decryptCBC(_data, CHUNK_SIZE);
                 }
+                _progress(decryptdata);
             } else {
                 // CONFIG::LOGGING {
                 // Log.info("no bytes available, stop timer");
                 // }
                 _timer.stop();
                 if (_data_complete) {
                     CONFIG::LOGGING {
-                    Log.debug("AES:data+decrypt completed, callback");
+                        Log.debug("AES:data+decrypt completed, callback");
                     }
                     // callback
                     _complete();
                 }
             }
         }
 
+        /* Cypher Block Chaining Decryption, refer to 
+         * http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher-block_chaining_
+         * for algorithm description
+         */
+        private function _decryptCBC(crypt : ByteArray, len : uint) : ByteArray {
+            var src : Vector.<uint> = new Vector.<uint>(4);
+            var dst : Vector.<uint> = new Vector.<uint>(4);
+            var decrypt : ByteArray = new ByteArray();
+            decrypt.length = len;
+
+            for (var i : uint = 0; i < len / 16; i++) {
+                // read src byte array
+                src[0] = crypt.readUnsignedInt();
+                src[1] = crypt.readUnsignedInt();
+                src[2] = crypt.readUnsignedInt();
+                src[3] = crypt.readUnsignedInt();
+
+                // AES decrypt src vector into dst vector
+                _key.decrypt128(src, dst);
+
+                // CBC : write output = XOR(decrypted,IV)
+                decrypt.writeUnsignedInt(dst[0] ^ iv0);
+                decrypt.writeUnsignedInt(dst[1] ^ iv1);
+                decrypt.writeUnsignedInt(dst[2] ^ iv2);
+                decrypt.writeUnsignedInt(dst[3] ^ iv3);
+
+                // CBC : next IV = (input)
+                iv0 = src[0];
+                iv1 = src[1];
+                iv2 = src[2];
+                iv3 = src[3];
+            }
+            decrypt.position = 0;
+            return decrypt;
+        }
+
+        public function unpad(a : ByteArray) : void {
+            var c : uint = a.length % 16;
+            if (c != 0) throw new Error("PKCS#5::unpad: ByteArray.length isn't a multiple of the blockSize");
+            c = a[a.length - 1];
+            for (var i : uint = c; i > 0; i--) {
+                var v : uint = a[a.length - 1];
+                a.length--;
+                if (c != v) throw new Error("PKCS#5:unpad: Invalid padding value. expected [" + c + "], found [" + v + "]");
+            }
+        }
+
         public function destroy() : void {
             _key.dispose();
             // _key = null;
-            _mode = null;
         }
     }
 }

src/org/mangui/hls/utils/FastAESKey.as

@@ -1,13 +1,11 @@
 package org.mangui.hls.utils {
     import flash.utils.ByteArray;
 
-    import com.hurlant.crypto.symmetric.ISymmetricKey;
-
     /* word based AES encryption/decryption
      * inspired by
      * https://code.google.com/p/crypto-js/source/browse/tags/3.1.2/src/aes.js
      */
-    public class FastAESKey implements ISymmetricKey {
+    public class FastAESKey {
         /* private data, specific to each key */
         private var keySize : uint;
         private var nRounds : uint;
@@ -19,10 +17,6 @@ package org.mangui.hls.utils {
         // static Lookup tables
         private static var _SBOX : Vector.<uint>;
         private static var _INV_SBOX : Vector.<uint>;
-        private static var _SUB_MIX_0 : Vector.<uint>;
-        private static var _SUB_MIX_1 : Vector.<uint>;
-        private static var _SUB_MIX_2 : Vector.<uint>;
-        private static var _SUB_MIX_3 : Vector.<uint>;
         private static var _INV_SUB_MIX_0 : Vector.<uint>;
         private static var _INV_SUB_MIX_1 : Vector.<uint>;
         private static var _INV_SUB_MIX_2 : Vector.<uint>;
@@ -35,10 +29,6 @@ package org.mangui.hls.utils {
         private static function _initTable() : void {
             _SBOX = new Vector.<uint>(256);
             _INV_SBOX = new Vector.<uint>(256);
-            _SUB_MIX_0 = new Vector.<uint>(256);
-            _SUB_MIX_1 = new Vector.<uint>(256);
-            _SUB_MIX_2 = new Vector.<uint>(256);
-            _SUB_MIX_3 = new Vector.<uint>(256);
             _INV_SUB_MIX_0 = new Vector.<uint>(256);
             _INV_SUB_MIX_1 = new Vector.<uint>(256);
             _INV_SUB_MIX_2 = new Vector.<uint>(256);
@@ -70,15 +60,8 @@ package org.mangui.hls.utils {
                 var x4 : uint = d[x2];
                 var x8 : uint = d[x4];
 
-                // Compute sub bytes, mix columns tables
-                var t : uint = (d[sx] * 0x101) ^ (sx * 0x1010100);
-                _SUB_MIX_0[x] = (t << 24) | (t >>> 8);
-                _SUB_MIX_1[x] = (t << 16) | (t >>> 16);
-                _SUB_MIX_2[x] = (t << 8) | (t >>> 24);
-                _SUB_MIX_3[x] = t;
-
                 // Compute inv sub bytes, inv mix columns tables
-                t = (x8 * 0x1010101) ^ (x4 * 0x10001) ^ (x2 * 0x101) ^ (x * 0x1010100);
+                var t: uint  = (x8 * 0x1010101) ^ (x4 * 0x10001) ^ (x2 * 0x101) ^ (x * 0x1010100);
                 _INV_SUB_MIX_0[sx] = (t << 24) | (t >>> 8);
                 _INV_SUB_MIX_1[sx] = (t << 16) | (t >>> 16);
                 _INV_SUB_MIX_2[sx] = (t << 8) | (t >>> 24);
@@ -152,27 +135,19 @@ package org.mangui.hls.utils {
                 }
             }
         }
-
-        public function decrypt(block : ByteArray, index : uint = 0) : void {
-            block.position = index;
-            for (var i : int = 0; i < keySize; i++) {
-                // state.push(block.readUnsignedInt());
-                state[i] = block.readUnsignedInt();
-            }
+
+        public function decrypt128(input : Vector.<uint>,output : Vector.<uint>) : void {
             // Swap 2nd and 4th rows
-            var t : uint = state[1];
-            state[1] = state[3];
-            state[3] = t;
-            _doCryptBlock(invKeySchedule, _INV_SUB_MIX_0, _INV_SUB_MIX_1, _INV_SUB_MIX_2, _INV_SUB_MIX_3, _INV_SBOX);
-            // Inv swap 2nd and 4th rows
-            t = state[1];
-            state[1] = state[3];
-            state[3] = t;
-
-            block.position = index;
-            for (i = 0; i < keySize; i++) {
-                block.writeUnsignedInt(state[i]);
-            }
+          state[0] = input[0];
+          state[1] = input[3];
+          state[2] = input[2];
+          state[3] = input[1];          
+          _doCryptBlock(invKeySchedule, _INV_SUB_MIX_0, _INV_SUB_MIX_1, _INV_SUB_MIX_2, _INV_SUB_MIX_3, _INV_SBOX);
+          // Inv swap 2nd and 4th rows
+          output[0] = state[0];
+          output[1] = state[3];
+          output[2] = state[2];
+          output[3] = state[1];
         }
 
         private function  _doCryptBlock(keySchedule : Vector.<uint>, SUB_MIX_0 : Vector.<uint>, SUB_MIX_1 : Vector.<uint>, SUB_MIX_2 : Vector.<uint>, SUB_MIX_3 : Vector.<uint>, SBOX : Vector.<uint>) : void {
@@ -220,26 +195,5 @@ package org.mangui.hls.utils {
             keyWords.length = 0;
             keyWords = null;
         }
-
-        public function encrypt(block : ByteArray, index : uint = 0) : void {
-            block.position = index;
-            for (var i : int = 0; i < keySize; i++) {
-                // state.push(block.readUnsignedInt());
-                state[i] = block.readUnsignedInt();
-            }
-            _doCryptBlock(keySchedule, _SUB_MIX_0, _SUB_MIX_1, _SUB_MIX_2, _SUB_MIX_3, _SBOX);
-            block.position = index;
-            for (i = 0; i < keySize; i++) {
-                block.writeUnsignedInt(state[i]);
-            }
-        }
-
-        public function getBlockSize() : uint {
-            return 16;
-        }
-
-        public function toString() : String {
-            return "aes" + (32 * keySize);
-        }
     }
 }