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PasswordDeriveBytes Constructor (Byte(), Byte(), CspParameters)

Initializes a new instance of the PasswordDeriveBytes class specifying the password, key salt, and cryptographic service provider (CSP) to use to derive the key.

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

Public Sub New ( _
	password As Byte(), _
	salt As Byte(), _
	cspParams As CspParameters _


Type: System.Byte()
The password to derive the key for.
Type: System.Byte()
The key salt to use to derive the key.
Type: System.Security.Cryptography.CspParameters
The cryptographic service provider (CSP) parameters for the operation.

Security noteSecurity Note

Never hard code a password within your source code. Hard-coded passwords can be retrieved from an assembly using the Ildasm.exe (MSIL Disassembler) l, a hex editor, or by simply opening up the assembly in a text editor such as Notepad.exe.

The following code example creates a key from a password using the PasswordDeriveBytes class.

Imports System
Imports System.Security.Cryptography
Imports System.Text

Module PasswordDerivedBytesExample

    Sub Main(ByVal args() As String)

        ' Get a password from the user.
        Console.WriteLine("Enter a password to produce a key:")

        Dim pwd As Byte() = Encoding.Unicode.GetBytes(Console.ReadLine())

        Dim salt As Byte() = CreateRandomSalt(7)

        ' Create a TripleDESCryptoServiceProvider object.
        Dim tdes As New TripleDESCryptoServiceProvider()

            Console.WriteLine("Creating a key with PasswordDeriveBytes...")

            ' Create a PasswordDeriveBytes object and then create 
            ' a TripleDES key from the password and salt.
            Dim pdb As New PasswordDeriveBytes(pwd, salt)

            ' Create the key and set it to the Key property
            ' of the TripleDESCryptoServiceProvider object.
            tdes.Key = pdb.CryptDeriveKey("TripleDES", "SHA1", 192, tdes.IV)

            Console.WriteLine("Operation complete.")
        Catch e As Exception
            ' Clear the buffers

            ' Clear the key.
        End Try


    End Sub

    '* Helper methods:
    '* createRandomSalt: Generates a random salt value of the 
    '*                   specified length.  
    '* clearBytes: Clear the bytes in a buffer so they can't 
    '*             later be read from memory.
    Function CreateRandomSalt(ByVal length As Integer) As Byte()
        ' Create a buffer
        Dim randBytes() As Byte

        If length >= 1 Then
            randBytes = New Byte(length) {}
            randBytes = New Byte(0) {}
        End If

        ' Create a new RNGCryptoServiceProvider.
        Dim rand As New RNGCryptoServiceProvider()

        ' Fill the buffer with random bytes.

        ' return the bytes.
        Return randBytes

    End Function

    Sub ClearBytes(ByVal buffer() As Byte)
        ' Check arguments.
        If buffer Is Nothing Then
            Throw New ArgumentException("buffer")
        End If

        ' Set each byte in the buffer to 0.
        Dim x As Integer
        For x = 0 To buffer.Length - 1
            buffer(x) = 0
        Next x

    End Sub
End Module

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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