/js/lib/Socket.IO-node/support/socket.io-client/lib/vendor/web-socket-js/flash-src/com/hurlant/crypto/hash/HMAC.as

/**

 * HMAC

 * 

 * An ActionScript 3 implementation of HMAC, Keyed-Hashing for Message

 * Authentication, as defined by RFC-2104

 * Copyright (c) 2007 Henri Torgemane

 * 

 * See LICENSE.txt for full license information.

 */

package com.hurlant.crypto.hash

{

	import flash.utils.ByteArray;

	import com.hurlant.util.Hex;

	

	public class HMAC implements IHMAC

	{

		private var hash:IHash;

		private var bits:uint;

		

		/**

		 * Create a HMAC object, using a Hash function, and 

		 * optionally a number of bits to return. 

		 * The HMAC will be truncated to that size if needed.

		 */

		public function HMAC(hash:IHash, bits:uint=0) {

			this.hash = hash;

			this.bits = bits;

		}

		



		public function getHashSize():uint {

			if (bits!=0) {

				return bits/8;

			} else {

				return hash.getHashSize();

			}

		}

		

		/**

		 * Compute a HMAC using a key and some data.

		 * It doesn't modify either, and returns a new ByteArray with the HMAC value.

		 */

		public function compute(key:ByteArray, data:ByteArray):ByteArray {

			var hashKey:ByteArray;

			if (key.length>hash.getInputSize()) {

				hashKey = hash.hash(key);

			} else {

				hashKey = new ByteArray;

				hashKey.writeBytes(key);

			}

			while (hashKey.length<hash.getInputSize()) {

				hashKey[hashKey.length]=0;

			}

			var innerKey:ByteArray = new ByteArray;

			var outerKey:ByteArray = new ByteArray;

			for (var i:uint=0;i<hashKey.length;i++) {

				innerKey[i] = hashKey[i] ^ 0x36;

				outerKey[i] = hashKey[i] ^ 0x5c;

			}

			// inner + data

			innerKey.position = hashKey.length;

			innerKey.writeBytes(data);

			var innerHash:ByteArray = hash.hash(innerKey);

			// outer + innerHash

			outerKey.position = hashKey.length;

			outerKey.writeBytes(innerHash);

			var outerHash:ByteArray = hash.hash(outerKey);

			if (bits>0 && bits<8*outerHash.length) {

				outerHash.length = bits/8;

			}

			return outerHash;

		}

		public function dispose():void {

			hash = null;

			bits = 0;

		}

		public function toString():String {

			return "hmac-"+(bits>0?bits+"-":"")+hash.toString();

		}

		

	}

}