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// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
//
namespace System.Security.Cryptography {
[System.Runtime.InteropServices.ComVisible(true)]
public class PKCS1MaskGenerationMethod : MaskGenerationMethod
{
private String HashNameValue;
//
// public constructors
//
public PKCS1MaskGenerationMethod() {
HashNameValue = "SHA1";
}
//
// public properties
//
public String HashName {
get { return HashNameValue; }
set {
HashNameValue = value;
if (HashNameValue == null) {
HashNameValue = "SHA1";
}
}
}
//
// public methods
//
public override byte[] GenerateMask(byte[] rgbSeed, int cbReturn)
{
HashAlgorithm hash = (HashAlgorithm) CryptoConfig.CreateFromName(HashNameValue);
byte[] rgbCounter = new byte[4];
byte[] rgbT = new byte[cbReturn];
uint counter = 0;
for (int ib=0; ib<rgbT.Length; ) {
// Increment counter -- up to 2^32 * sizeof(Hash)
Utils.ConvertIntToByteArray(counter++, ref rgbCounter);
hash.TransformBlock(rgbSeed, 0, rgbSeed.Length, rgbSeed, 0);
hash.TransformFinalBlock(rgbCounter, 0, 4);
byte[] _hash = hash.Hash;
hash.Initialize();
if (rgbT.Length - ib > _hash.Length) {
Buffer.BlockCopy(_hash, 0, rgbT, ib, _hash.Length);
} else {
Buffer.BlockCopy(_hash, 0, rgbT, ib, rgbT.Length - ib);
}
ib += hash.Hash.Length;
}
return rgbT;
}
}
}
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