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PasswordDeriveBytes.PasswordDeriveBytes(Byte[], Byte[]) Constructor

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() _
)
'Usage
Dim password As Byte()
Dim salt As Byte()

Dim instance As New PasswordDeriveBytes(password, salt)
public PasswordDeriveBytes (
	byte[] password, 
	byte[] salt
)
public function PasswordDeriveBytes (
	password : byte[], 
	salt : byte[]
)
Not applicable.

Parameters

password

The password to derive the key for.

salt

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 MSIL Disassembler (Ildasm.exe), 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

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

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

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