Rfc2898DeriveBytes Class

Note: This class is new in the .NET Framework version 2.0.

Implements password-based key derivation functionality, PBKDF2, by using a pseudo-random number generator based on HMACSHA1.

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

<ComVisibleAttribute(True)> _
Public Class Rfc2898DeriveBytes
	Inherits DeriveBytes
Dim instance As Rfc2898DeriveBytes

/** @attribute ComVisibleAttribute(true) */ 
public class Rfc2898DeriveBytes extends DeriveBytes
public class Rfc2898DeriveBytes extends DeriveBytes

Rfc2898DeriveBytes takes a password, a salt, and an iteration count, and then generates keys through calls to the GetBytes method.

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 at http://www.rfc-editor.org. 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 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 uses the Rfc2898DeriveBytes class to create two identical keys for the TripleDES class. It then encrypts and decrypts some data using the keys.

No code example is currently available or this language may not be supported.
import System.*;
import System.IO.*;
import System.Text.*;
import 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 static String usageText = "Usage: RFC2898 <password>\n"
        + "You must specify the password for encryption.\n";

    public static void main(String[] passwordArgs)
        //If no file name is specified, write usage text.
        if (passwordArgs.get_Length() == 0) {
        else {
            String pwd1 = (String)passwordArgs.get_Item(0);

            ubyte salt1[] = new ubyte[] { 0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6,
                0xF1, 0xF0, 0xEE, 0x21, 0x22, 0x45 };
            //data1 can be a string or contents of a file.
            String data1 = "Some test data";
            //The default iteration count is 1000 so the two methods use the
            //same iteration count.
            int myIterations = 1000;
            try {
                Rfc2898DeriveBytes k1 = new Rfc2898DeriveBytes(pwd1, salt1,
                Rfc2898DeriveBytes k2 = new Rfc2898DeriveBytes(pwd1, salt1);
                // Encrypt the data.
                TripleDES encAlg = TripleDES.Create();
                MemoryStream encryptionStream = new MemoryStream();
                CryptoStream encrypt = new CryptoStream(encryptionStream, 
                    encAlg.CreateEncryptor(), CryptoStreamMode.Write);
                ubyte utfD1[] = (new System.Text.UTF8Encoding(false)).
                encrypt.Write(utfD1, 0, utfD1.get_Length());
                ubyte eData1[] = encryptionStream.ToArray();
                // Try to decrypt, thus showing it can be round-tripped.
                TripleDES decAlg = TripleDES.Create();
                MemoryStream decryptionStreamBacking = new MemoryStream();
                CryptoStream decrypt = new CryptoStream(decryptionStreamBacking, 
                    decAlg.CreateDecryptor(), CryptoStreamMode.Write);
                decrypt.Write(eData1, 0, eData1.get_Length());
                String data2 = (new UTF8Encoding(false)).
                if (!(data1.Equals(data2))) {
                    Console.WriteLine("Error: The two values are not equal.");
                else {
                    Console.WriteLine("The two values are equal.");
                    Console.WriteLine("k1 iterations: {0}", (System.Int32)k1.
                    Console.WriteLine("k2 iterations: {0}", (System.Int32)k2.
            catch (System.Exception e) {
                Console.WriteLine("Error: ", e);
    } //main
} //rfc2898test


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 98, Windows 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 .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0

Community Additions