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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 {
using System.Globalization;
using System.Diagnostics.Contracts;
[System.Runtime.InteropServices.ComVisible(true)]
public class RSAPKCS1KeyExchangeFormatter : AsymmetricKeyExchangeFormatter {
RandomNumberGenerator RngValue;
RSA _rsaKey;
//
// public constructors
//
public RSAPKCS1KeyExchangeFormatter() {}
public RSAPKCS1KeyExchangeFormatter(AsymmetricAlgorithm key) {
if (key == null)
throw new ArgumentNullException("key");
Contract.EndContractBlock();
_rsaKey = (RSA) key;
}
//
// public properties
//
public override String Parameters {
get { return "<enc:KeyEncryptionMethod enc:Algorithm=\"http://www.microsoft.com/xml/security/algorithm/PKCS1-v1.5-KeyEx\" xmlns:enc=\"http://www.microsoft.com/xml/security/encryption/v1.0\" />"; }
}
public RandomNumberGenerator Rng {
get { return RngValue; }
set { RngValue = value; }
}
//
// public methods
//
public override void SetKey(AsymmetricAlgorithm key) {
if (key == null)
throw new ArgumentNullException("key");
Contract.EndContractBlock();
_rsaKey = (RSA) key;
}
public override byte[] CreateKeyExchange(byte[] rgbData) {
if (_rsaKey == null)
throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_MissingKey"));
byte[] rgbKeyEx;
if (_rsaKey is RSACryptoServiceProvider) {
rgbKeyEx = ((RSACryptoServiceProvider) _rsaKey).Encrypt(rgbData, false);
}
else {
int cb = _rsaKey.KeySize/8;
if ((rgbData.Length + 11) > cb)
throw new CryptographicException(Environment.GetResourceString("Cryptography_Padding_EncDataTooBig", cb-11));
byte[] rgbInput = new byte[cb];
//
// We want to pad to the following format:
// 00 || 02 || PS || 00 || D
//
// PS - pseudorandom non zero bytes
// D - data
//
if (RngValue == null) {
RngValue = RandomNumberGenerator.Create();
}
Rng.GetNonZeroBytes(rgbInput);
rgbInput[0] = 0;
rgbInput[1] = 2;
rgbInput[cb-rgbData.Length-1] = 0;
Buffer.InternalBlockCopy(rgbData, 0, rgbInput, cb-rgbData.Length, rgbData.Length);
//
// Now encrypt the value and return it. (apply public key)
//
rgbKeyEx = _rsaKey.EncryptValue(rgbInput);
}
return rgbKeyEx;
}
public override byte[] CreateKeyExchange(byte[] rgbData, Type symAlgType) {
return CreateKeyExchange(rgbData);
}
}
}
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