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source/com/hurlant/crypto/symmetric/OFBMode.as

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+/**
+ * OFBMode
+ * 
+ * An ActionScript 3 implementation of the OFB confidentiality mode
+ * Copyright (c) 2007 Henri Torgemane
+ * 
+ * See LICENSE.txt for full license information.
+ */
+package com.hurlant.crypto.symmetric
+{
+	import flash.utils.ByteArray;
+
+	public class OFBMode extends IVMode implements IMode
+	{
+		public function OFBMode(key:ISymmetricKey, padding:IPad=null)
+		{
+			super(key, null);
+		}
+		
+		public function encrypt(src:ByteArray):void
+		{
+			var vector:ByteArray = getIV4e();
+			core(src, vector);
+		}
+		
+		public function decrypt(src:ByteArray):void
+		{
+			var vector:ByteArray = getIV4d();
+			core(src, vector);
+		}
+		
+		private function core(src:ByteArray, iv:ByteArray):void { 
+			var l:uint = src.length;
+			var tmp:ByteArray = new ByteArray;
+			for (var i:uint=0;i<src.length;i+=blockSize) {
+				key.encrypt(iv);
+				tmp.position=0;
+				tmp.writeBytes(iv);
+				var chunk:uint = (i+blockSize<l)?blockSize:l-i;
+				for (var j:uint=0;j<chunk;j++) {
+					src[i+j] ^= iv[j];
+				}
+				iv.position=0;
+				iv.writeBytes(tmp);
+			}
+		}
+		public function toString():String {
+			return key.toString()+"-ofb";
+		}
+		
+	}
+}