Rfc2898DeriveBytes Constructor (String, Byte[])

Rfc2898DeriveBytes Constructor (String, Byte())

Initializes a new instance of the Rfc2898DeriveBytes class using a password and salt to derive the key.

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

Public Sub New ( _
	password As String, _
	salt As Byte() _
Dim password As String 
Dim salt As Byte()

Dim instance As New Rfc2898DeriveBytes(password, _


Type: System.String

The password used to derive the key.

Type: System.Byte()

The key salt used to derive the key.


The specified salt size is smaller than 8 bytes or the iteration count is less than 1.


The password or salt is Nothing.

The salt size must be 8 bytes or larger.

RFC 2898 includes methods for creating a key and initialization vector (IV) from a password and salt. You can use PBKDF2, a password-based key derivation function, to derive keys using a pseudo-random function that allows keys of virtually unlimited length to be generated. The Rfc2898DeriveBytes class can be used to produce a derived key from a base key and other parameters. In a password-based key derivation function, the base key is a password and the other parameters are a salt value and an iteration count.

For more information about PBKDF2, see RFC 2898, "PKCS #5: Password-Based Cryptography Specification Version 2.0," available on the Request for Comments Web site. See section 5.2, "PBKDF2," for complete details.

Security noteSecurity Note:

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

The following code example uses the Rfc2898DeriveBytes class to create two identical keys for the TripleDES class. It then encrypts and decrypts some data using the keys.

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

Public Class rfc2898test
    ' Generate a key k1 with password pwd1 and salt salt1. 
    ' Generate a key k2 with password pwd1 and salt salt1. 
    ' Encrypt data1 with key k1 using symmetric encryption, creating edata1. 
    ' Decrypt edata1 with key k2 using symmetric decryption, creating data2. 
    ' data2 should equal data1. 
    Private Const usageText As String = "Usage: RFC2898 <password>" + vbLf + "You must specify the password for encryption." + vbLf

    Public Shared Sub Main(ByVal passwordargs() As String)
        'If no file name is specified, write usage text. 
        If passwordargs.Length = 0 Then
            Dim pwd1 As String = passwordargs(0)

            Dim salt1(8) As Byte
            Using rngCsp As New RNGCryptoServiceProvider()
            End Using 
            'data1 can be a string or contents of a file. 
            Dim data1 As String = "Some test data" 
            'The default iteration count is 1000 so the two methods use the same iteration count. 
            Dim myIterations As Integer = 1000
                Dim k1 As New Rfc2898DeriveBytes(pwd1, salt1, myIterations)
                Dim k2 As New Rfc2898DeriveBytes(pwd1, salt1)
                ' Encrypt the data. 
                Dim encAlg As TripleDES = TripleDES.Create()
                encAlg.Key = k1.GetBytes(16)
                Dim encryptionStream As New MemoryStream()
                Dim encrypt As New CryptoStream(encryptionStream, encAlg.CreateEncryptor(), CryptoStreamMode.Write)
                Dim utfD1 As Byte() = New System.Text.UTF8Encoding(False).GetBytes(data1)
                encrypt.Write(utfD1, 0, utfD1.Length)
                Dim edata1 As Byte() = encryptionStream.ToArray()

                ' Try to decrypt, thus showing it can be round-tripped. 
                Dim decAlg As TripleDES = TripleDES.Create()
                decAlg.Key = k2.GetBytes(16)
                decAlg.IV = encAlg.IV
                Dim decryptionStreamBacking As New MemoryStream()
                Dim decrypt As New CryptoStream(decryptionStreamBacking, decAlg.CreateDecryptor(), CryptoStreamMode.Write)
                decrypt.Write(edata1, 0, edata1.Length)
                Dim data2 As String = New UTF8Encoding(False).GetString(decryptionStreamBacking.ToArray())

                If Not data1.Equals(data2) Then
                    Console.WriteLine("Error: The two values are not equal.")
                    Console.WriteLine("The two values are equal.")
                    Console.WriteLine("k1 iterations: {0}", k1.IterationCount)
                    Console.WriteLine("k2 iterations: {0}", k2.IterationCount)
                End If 
            Catch e As Exception
                Console.WriteLine("Error: ", e)
            End Try 
        End If 

    End Sub 
End Class

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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