Derives a key from a password using an extension of the PBKDF1 algorithm.
Namespace:
System.Security.Cryptography
Assembly:
mscorlib (in mscorlib.dll)
Visual Basic (Declaration)
<ComVisibleAttribute(True)> _
Public Class PasswordDeriveBytes _
Inherits DeriveBytes
Dim instance As PasswordDeriveBytes
[ComVisibleAttribute(true)]
public class PasswordDeriveBytes : DeriveBytes
[ComVisibleAttribute(true)]
public ref class PasswordDeriveBytes : public DeriveBytes
public class PasswordDeriveBytes extends DeriveBytes
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: |
|---|
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
using System;
using System.Security.Cryptography;
using System.Text;
public class PasswordDerivedBytesExample
{
public static void Main(String[] args)
{
// Get a password from the user.
Console.WriteLine("Enter a password to produce a key:");
byte[] pwd = Encoding.Unicode.GetBytes(Console.ReadLine());
byte[] salt = CreateRandomSalt(7);
// Create a TripleDESCryptoServiceProvider object.
TripleDESCryptoServiceProvider tdes = 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.
PasswordDeriveBytes pdb = 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 (Exception e)
{
Console.WriteLine(e.Message);
}
finally
{
// Clear the buffers
ClearBytes(pwd);
ClearBytes(salt);
// Clear the key.
tdes.Clear();
}
Console.ReadLine();
}
//////////////////////////////////////////////////////////
// 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.
//////////////////////////////////////////////////////////
public static byte[] CreateRandomSalt(int length)
{
// Create a buffer
byte[] randBytes;
if (length >= 1)
{
randBytes = new byte[length];
}
else
{
randBytes = new byte[1];
}
// Create a new RNGCryptoServiceProvider.
RNGCryptoServiceProvider rand = new RNGCryptoServiceProvider();
// Fill the buffer with random bytes.
rand.GetBytes(randBytes);
// return the bytes.
return randBytes;
}
public static void ClearBytes(byte[] buffer)
{
// Check arguments.
if (buffer == null)
{
throw new ArgumentException("buffer");
}
// Set each byte in the buffer to 0.
for (int x = 0; x < buffer.Length; x++)
{
buffer[x] = 0;
}
}
}
using namespace System;
using namespace System::Security::Cryptography;
using namespace System::Text;
// Generates a random salt value of the specified length.
array<Byte>^ CreateRandomSalt(int length)
{
// Create a buffer
array<Byte>^ randomBytes;
if (length >= 1)
{
randomBytes = gcnew array <Byte>(length);
}
else
{
randomBytes = gcnew array <Byte>(1);
}
// Create a new RNGCryptoServiceProvider.
RNGCryptoServiceProvider^ cryptoRNGProvider =
gcnew RNGCryptoServiceProvider();
// Fill the buffer with random bytes.
cryptoRNGProvider->GetBytes(randomBytes);
// return the bytes.
return randomBytes;
}
// Clears the bytes in a buffer so they can't later be read from memory.
void ClearBytes(array<Byte>^ buffer)
{
// Check arguments.
if (buffer == nullptr)
{
throw gcnew ArgumentNullException("buffer");
}
// Set each byte in the buffer to 0.
for (int x = 0; x <= buffer->Length - 1; x++)
{
buffer[x] = 0;
}
}
int main(array<String^>^ args)
{
// Get a password from the user.
Console::WriteLine("Enter a password to produce a key:");
// Security Note: Never hard-code a password within your
// source code. Hard-coded passwords can be retrieved
// from a compiled assembly.
array<Byte>^ password = Encoding::Unicode->GetBytes(Console::ReadLine());
array<Byte>^ randomSalt = CreateRandomSalt(7);
// Create a TripleDESCryptoServiceProvider object.
TripleDESCryptoServiceProvider^ cryptoDESProvider =
gcnew TripleDESCryptoServiceProvider();
try
{
Console::WriteLine("Creating a key with PasswordDeriveBytes...");
// Create a PasswordDeriveBytes object and then create
// a TripleDES key from the password and salt.
PasswordDeriveBytes^ passwordDeriveBytes = gcnew PasswordDeriveBytes
(password->ToString(), randomSalt);
// Create the key and set it to the Key property
// of the TripleDESCryptoServiceProvider object.
cryptoDESProvider->Key = passwordDeriveBytes->CryptDeriveKey
("TripleDES", "SHA1", 192, cryptoDESProvider->IV);
Console::WriteLine("Operation complete.");
}
catch (Exception^ ex)
{
Console::WriteLine(ex->Message);
}
finally
{
// Clear the buffers
ClearBytes(password);
ClearBytes(randomSalt);
// Clear the key.
cryptoDESProvider->Clear();
}
Console::ReadLine();
}
System..::.Object
System.Security.Cryptography..::.DeriveBytes
System.Security.Cryptography..::.PasswordDeriveBytes
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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, 1.1, 1.0
Reference
Other Resources