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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)

public PasswordDeriveBytes(
	byte[] password,
	byte[] salt
)

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.

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;
        }
    }
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 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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