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PasswordDeriveBytes Constructor (Byte(), Byte())

Initializes a new instance of the PasswordDeriveBytes class specifying the password and key salt to use to derive the key.

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

'Declaration
Public Sub New ( _
	password As Byte(), _
	salt As Byte() _
)

Parameters

password
Type: System.Byte()

The password to derive the key for.

salt
Type: System.Byte()

The key salt to use to derive the key.

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 (IL Disassembler), 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()

        Try
            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
            Console.WriteLine(e.Message)
        Finally 
            ' Clear the buffers
            ClearBytes(pwd)
            ClearBytes(salt)

            ' Clear the key.
            tdes.Clear()
        End Try

        Console.ReadLine()

    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) {}
        Else
            randBytes = New Byte(0) {}
        End If 

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

        ' Fill the buffer with random bytes.
        rand.GetBytes(randBytes)

        ' 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: 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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