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ProtectedData.Unprotect Method

Unprotects the encryptedData parameter and returns a byte array.

Namespace:  System.Security.Cryptography
Assembly:  System.Security (in System.Security.dll)
public static byte[] Unprotect(
	byte[] encryptedData,
	byte[] optionalEntropy,
	DataProtectionScope scope
)

Parameters

encryptedData
Type: System.Byte[]

A byte array containing data encrypted using the Protect method.

optionalEntropy
Type: System.Byte[]

An additional byte array used to encrypt the data.

scope
Type: System.Security.Cryptography.DataProtectionScope

One of the DataProtectionScope values.

Return Value

Type: System.Byte[]
A byte array representing the unprotected data.
ExceptionCondition
ArgumentNullException

The encryptedData parameter is null.

CryptographicException

The cryptographic protection failed.

PlatformNotSupportedException

The operating system does not support this method.

OutOfMemoryException

Out of memory.

This method can be used to unprotect data that was encrypted using the Protect method. If the optionalEntropy parameter was used during encryption, it must be supplied to unencrypt the data.

NoteNote:

If you use this method during impersonation, you may receive the following error: "Key not valid for use in specified state." This error can be prevented by loading the profile of the user you want to impersonate, before calling the method.

The following code example shows how to use data protection.

using System;
using System.Security.Cryptography;

public class DataProtectionSample
{
// Create byte array for additional entropy when using Protect method. 
	static byte [] s_aditionalEntropy = { 9, 8, 7, 6, 5 };

	public static void Main()
	{
// Create a simple byte array containing data to be encrypted.
		
byte [] secret = { 0, 1, 2, 3, 4, 1, 2, 3, 4 };

//Encrypt the data.
		byte [] encryptedSecret = Protect( secret );
		Console.WriteLine("The encrypted byte array is:");
		PrintValues(encryptedSecret);
		
// Decrypt the data and store in a byte array.
		byte [] originalData = Unprotect( encryptedSecret );
		Console.WriteLine("{0}The original data is:", Environment.NewLine);
		PrintValues(originalData);

	}

	public static byte [] Protect( byte [] data )
	{
		try
		{
			// Encrypt the data using DataProtectionScope.CurrentUser. The result can be decrypted 
			//  only by the same current user. 
			return ProtectedData.Protect( data, s_aditionalEntropy, DataProtectionScope.CurrentUser );
		} 
		catch (CryptographicException e)
		{
			Console.WriteLine("Data was not encrypted. An error occurred.");
			Console.WriteLine(e.ToString());
			return null;
		}
	}

	public static byte [] Unprotect( byte [] data )
	{
		try
		{
			//Decrypt the data using DataProtectionScope.CurrentUser. 
			return ProtectedData.Unprotect( data, s_aditionalEntropy, DataProtectionScope.CurrentUser );
		} 
		catch (CryptographicException e)
		{
			Console.WriteLine("Data was not decrypted. An error occurred.");
			Console.WriteLine(e.ToString());
			return null;
		}
	}

	public static void PrintValues( Byte[] myArr )  
	{
	      foreach ( Byte i in myArr )  
		  	{
		         Console.Write( "\t{0}", i );
			 }
      Console.WriteLine();
	 }

}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0
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