PasswordDeriveBytes Class
Derives a key from a password using an extension of the PBKDF1 algorithm.
Assembly: mscorlib (in mscorlib.dll)
This class uses an extension of the PBKDF1 algorithm defined in the PKCS#5 v2.0 standard to derive bytes suitable for use as key material from a password. The standard is documented in IETF RRC 2898.
Security Note: |
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Never hard-code a password within your source code. Hard coded passwords can be retrieved from an assembly using the MSIL Disassembler (Ildasm.exe) tool, a hex editor, or by simply opening up the assembly in a text editor like 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
System.Security.Cryptography.DeriveBytes
System.Security.Cryptography.PasswordDeriveBytes
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.
Security Note: