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/**
* 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();
}
}
}
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