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ProtectedData.Protect Method (Byte(), Byte(), DataProtectionScope)

 

Encrypts the data in a specified byte array and returns a byte array that contains the encrypted data.

Namespace:   System.Security.Cryptography
Assembly:  System.Security (in System.Security.dll)

Public Shared Function Protect (
	userData As Byte(),
	optionalEntropy As Byte(),
	scope As DataProtectionScope
) As Byte()

Parameters

userData
Type: System.Byte()

A byte array that contains data to encrypt.

optionalEntropy
Type: System.Byte()

An optional additional byte array used to increase the complexity of the encryption, or null for no additional complexity.

scope
Type: System.Security.Cryptography.DataProtectionScope

One of the enumeration values that specifies the scope of encryption.

Return Value

Type: System.Byte()

A byte array representing the encrypted data.

Exception Condition
ArgumentNullException

The userData parameter is null.

CryptographicException

The encryption failed.

NotSupportedException

The operating system does not support this method.

OutOfMemoryException

The system ran out of memory while encrypting the data.

This method can be used to encrypt data such as passwords, keys, or connection strings. The optionalEntropy parameter enables you to add data to increase the complexity of the encryption; specify null for no additional complexity. If provided, this information must also be used when decrypting the data using the Unprotect method.

System_CAPS_noteNote

If you use this method during impersonation, you may receive the following error: "Key not valid for use in specified state." To prevent this error, load the profile of the user you want to impersonate before calling the method.

The following example shows how to use data protection.

Imports System
Imports System.Security.Cryptography



Public Class DataProtectionSample
    ' Create byte array for additional entropy when using Protect method.
    Private Shared s_aditionalEntropy As Byte() = {9, 8, 7, 6, 5}


    Public Shared Sub Main()
        ' Create a simple byte array containing data to be encrypted.
        Dim secret As Byte() = {0, 1, 2, 3, 4, 1, 2, 3, 4}

        'Encrypt the data.
        Dim encryptedSecret As Byte() = Protect(secret)
        Console.WriteLine("The encrypted byte array is:")
        PrintValues(encryptedSecret)

        ' Decrypt the data and store in a byte array.
        Dim originalData As Byte() = Unprotect(encryptedSecret)
        Console.WriteLine("{0}The original data is:", Environment.NewLine)
        PrintValues(originalData)

    End Sub


    Public Shared Function Protect(ByVal data() As Byte) As Byte()
        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 e As CryptographicException
            Console.WriteLine("Data was not encrypted. An error occurred.")
            Console.WriteLine(e.ToString())
            Return Nothing
        End Try

    End Function


    Public Shared Function Unprotect(ByVal data() As Byte) As Byte()
        Try
            'Decrypt the data using DataProtectionScope.CurrentUser.
            Return ProtectedData.Unprotect(data, s_aditionalEntropy, DataProtectionScope.CurrentUser)
        Catch e As CryptographicException
            Console.WriteLine("Data was not decrypted. An error occurred.")
            Console.WriteLine(e.ToString())
            Return Nothing
        End Try

    End Function


    Public Shared Sub PrintValues(ByVal myArr() As [Byte])
        Dim i As [Byte]
        For Each i In myArr
            Console.Write(vbTab + "{0}", i)
        Next i
        Console.WriteLine()

    End Sub
End Class

DataProtectionPermission

with the associated ProtectData flag for permission to protect data.

.NET Framework
Available since 2.0
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