Rfc2898DeriveBytes Rfc2898DeriveBytes Rfc2898DeriveBytes Rfc2898DeriveBytes Class

Definition

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

public ref class Rfc2898DeriveBytes : System::Security::Cryptography::DeriveBytes
[System.Runtime.InteropServices.ComVisible(true)]
public class Rfc2898DeriveBytes : System.Security.Cryptography.DeriveBytes
type Rfc2898DeriveBytes = class
    inherit DeriveBytes
Public Class Rfc2898DeriveBytes
Inherits DeriveBytes
Inheritance
Rfc2898DeriveBytesRfc2898DeriveBytesRfc2898DeriveBytesRfc2898DeriveBytes
Attributes

Examples

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.

using namespace System;
using namespace System::IO;
using namespace System::Text;
using namespace System::Security::Cryptography;

// 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.

int main()
{
   array<String^>^passwordargs = Environment::GetCommandLineArgs();
   String^ usageText = "Usage: RFC2898 <password>\nYou must specify the password for encryption.\n";

   //If no file name is specified, write usage text.
   if ( passwordargs->Length == 1 )
   {
      Console::WriteLine( usageText );
   }
   else
   {
      String^ pwd1 = passwordargs[ 1 ];
      
      array<Byte>^salt1 = gcnew array<Byte>(8);
	  RNGCryptoServiceProvider ^ rngCsp = gcnew RNGCryptoServiceProvider();
		 rngCsp->GetBytes(salt1);
      //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 = gcnew Rfc2898DeriveBytes( pwd1,salt1,myIterations );
         Rfc2898DeriveBytes ^ k2 = gcnew Rfc2898DeriveBytes( pwd1,salt1 );

         // Encrypt the data.
         TripleDES^ encAlg = TripleDES::Create();
         encAlg->Key = k1->GetBytes( 16 );
         MemoryStream^ encryptionStream = gcnew MemoryStream;
         CryptoStream^ encrypt = gcnew CryptoStream( encryptionStream,encAlg->CreateEncryptor(),CryptoStreamMode::Write );
         array<Byte>^utfD1 = (gcnew System::Text::UTF8Encoding( false ))->GetBytes( data1 );

         encrypt->Write( utfD1, 0, utfD1->Length );
         encrypt->FlushFinalBlock();
         encrypt->Close();
         array<Byte>^edata1 = encryptionStream->ToArray();
         k1->Reset();

         // Try to decrypt, thus showing it can be round-tripped.
         TripleDES^ decAlg = TripleDES::Create();
         decAlg->Key = k2->GetBytes( 16 );
         decAlg->IV = encAlg->IV;
         MemoryStream^ decryptionStreamBacking = gcnew MemoryStream;
         CryptoStream^ decrypt = gcnew CryptoStream( decryptionStreamBacking,decAlg->CreateDecryptor(),CryptoStreamMode::Write );

         decrypt->Write( edata1, 0, edata1->Length );
         decrypt->Flush();
         decrypt->Close();
         k2->Reset();

         String^ data2 = (gcnew UTF8Encoding( false ))->GetString( decryptionStreamBacking->ToArray() );
         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}", k1->IterationCount );
            Console::WriteLine( "k2 iterations: {0}", k2->IterationCount );
         }
      }

      catch ( Exception^ e ) 
      {
         Console::WriteLine( "Error: ", e );
      }
   }
}
using System;
using System.IO;
using System.Text;
using 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 const string usageText = "Usage: RFC2898 <password>\nYou must 
specify the password for encryption.\n";
    public static void Main(string[] passwordargs)
    {
        //If no file name is specified, write usage text.
        if (passwordargs.Length == 0)
        {
            Console.WriteLine(usageText);
        }
        else
        {
            string pwd1 = passwordargs[0];
            // Create a byte array to hold the random value. 
            byte[] salt1 = new byte[8];
            using (RNGCryptoServiceProvider rngCsp = new 
RNGCryptoServiceProvider())
            {
                // Fill the array with a random value.
                rngCsp.GetBytes(salt1);
            }

            //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, 
myIterations);
                Rfc2898DeriveBytes k2 = new Rfc2898DeriveBytes(pwd1, salt1);
                // Encrypt the data.
                TripleDES encAlg = TripleDES.Create();
                encAlg.Key = k1.GetBytes(16);
                MemoryStream encryptionStream = new MemoryStream();
                CryptoStream encrypt = new CryptoStream(encryptionStream, 
encAlg.CreateEncryptor(), CryptoStreamMode.Write);
                byte[] utfD1 = new System.Text.UTF8Encoding(false).GetBytes(
data1);

                encrypt.Write(utfD1, 0, utfD1.Length);
                encrypt.FlushFinalBlock();
                encrypt.Close();
                byte[] edata1 = encryptionStream.ToArray();
                k1.Reset();

                // Try to decrypt, thus showing it can be round-tripped.
                TripleDES decAlg = TripleDES.Create();
                decAlg.Key = k2.GetBytes(16);
                decAlg.IV = encAlg.IV;
                MemoryStream decryptionStreamBacking = new MemoryStream();
                CryptoStream decrypt = new CryptoStream(
decryptionStreamBacking, decAlg.CreateDecryptor(), CryptoStreamMode.Write);
                decrypt.Write(edata1, 0, edata1.Length);
                decrypt.Flush();
                decrypt.Close();
                k2.Reset();
                string data2 = new UTF8Encoding(false).GetString(
decryptionStreamBacking.ToArray());

                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}", k1.IterationCount);
                    Console.WriteLine("k2 iterations: {0}", k2.IterationCount);
                }
            }
            catch (Exception e)
            {
                Console.WriteLine("Error: ", e);
            }

        }
    }
}
Imports System
Imports System.IO
Imports System.Text
Imports 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 Const usageText As String = "Usage: RFC2898 <password>" + vbLf + "You must specify the password for encryption." + vbLf

    Public Shared Sub Main(ByVal passwordargs() As String)
        'If no file name is specified, write usage text.
        If passwordargs.Length = 0 Then
            Console.WriteLine(usageText)
        Else
            Dim pwd1 As String = passwordargs(0)

            Dim salt1(8) As Byte
            Using rngCsp As New RNGCryptoServiceProvider()
                rngCsp.GetBytes(salt1)
            End Using
            'data1 can be a string or contents of a file.
            Dim data1 As String = "Some test data"
            'The default iteration count is 1000 so the two methods use the same iteration count.
            Dim myIterations As Integer = 1000
            Try
                Dim k1 As New Rfc2898DeriveBytes(pwd1, salt1, myIterations)
                Dim k2 As New Rfc2898DeriveBytes(pwd1, salt1)
                ' Encrypt the data.
                Dim encAlg As TripleDES = TripleDES.Create()
                encAlg.Key = k1.GetBytes(16)
                Dim encryptionStream As New MemoryStream()
                Dim encrypt As New CryptoStream(encryptionStream, encAlg.CreateEncryptor(), CryptoStreamMode.Write)
                Dim utfD1 As Byte() = New System.Text.UTF8Encoding(False).GetBytes(data1)
                encrypt.Write(utfD1, 0, utfD1.Length)
                encrypt.FlushFinalBlock()
                encrypt.Close()
                Dim edata1 As Byte() = encryptionStream.ToArray()
                k1.Reset()

                ' Try to decrypt, thus showing it can be round-tripped.
                Dim decAlg As TripleDES = TripleDES.Create()
                decAlg.Key = k2.GetBytes(16)
                decAlg.IV = encAlg.IV
                Dim decryptionStreamBacking As New MemoryStream()
                Dim decrypt As New CryptoStream(decryptionStreamBacking, decAlg.CreateDecryptor(), CryptoStreamMode.Write)
                decrypt.Write(edata1, 0, edata1.Length)
                decrypt.Flush()
                decrypt.Close()
                k2.Reset()
                Dim data2 As String = New UTF8Encoding(False).GetString(decryptionStreamBacking.ToArray())

                If Not data1.Equals(data2) Then
                    Console.WriteLine("Error: The two values are not equal.")
                Else
                    Console.WriteLine("The two values are equal.")
                    Console.WriteLine("k1 iterations: {0}", k1.IterationCount)
                    Console.WriteLine("k2 iterations: {0}", k2.IterationCount)
                End If
            Catch e As Exception
                Console.WriteLine("Error: ", e)
            End Try
        End If

    End Sub
End Class

Remarks

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. See section 5.2, "PBKDF2," for complete details.

Important

Never hard-code a password within your source code. Hard-coded passwords can be retrieved from an assembly by using the Ildasm.exe (IL Disassembler), by using a hexadecimal editor, or by simply opening up the assembly in a text editor such as Notepad.exe.

Constructors

Rfc2898DeriveBytes(Byte[], Byte[], Int32) Rfc2898DeriveBytes(Byte[], Byte[], Int32) Rfc2898DeriveBytes(Byte[], Byte[], Int32) Rfc2898DeriveBytes(Byte[], Byte[], Int32)

Initializes a new instance of the Rfc2898DeriveBytes class using a password, a salt, and number of iterations to derive the key.

Rfc2898DeriveBytes(Byte[], Byte[], Int32, HashAlgorithmName) Rfc2898DeriveBytes(Byte[], Byte[], Int32, HashAlgorithmName) Rfc2898DeriveBytes(Byte[], Byte[], Int32, HashAlgorithmName) Rfc2898DeriveBytes(Byte[], Byte[], Int32, HashAlgorithmName)

Initializes a new instance of the Rfc2898DeriveBytes class using the specified password, salt, number of iterations and the hash algorithm name to derive the key.

Rfc2898DeriveBytes(String, Byte[]) Rfc2898DeriveBytes(String, Byte[]) Rfc2898DeriveBytes(String, Byte[]) Rfc2898DeriveBytes(String, Byte[])

Initializes a new instance of the Rfc2898DeriveBytes class using a password and salt to derive the key.

Rfc2898DeriveBytes(String, Byte[], Int32) Rfc2898DeriveBytes(String, Byte[], Int32) Rfc2898DeriveBytes(String, Byte[], Int32) Rfc2898DeriveBytes(String, Byte[], Int32)

Initializes a new instance of the Rfc2898DeriveBytes class using a password, a salt, and number of iterations to derive the key.

Rfc2898DeriveBytes(String, Byte[], Int32, HashAlgorithmName) Rfc2898DeriveBytes(String, Byte[], Int32, HashAlgorithmName) Rfc2898DeriveBytes(String, Byte[], Int32, HashAlgorithmName) Rfc2898DeriveBytes(String, Byte[], Int32, HashAlgorithmName)

Initializes a new instance of the Rfc2898DeriveBytes class using the specified password, salt, number of iterations and the hash algorithm name to derive the key.

Rfc2898DeriveBytes(String, Int32) Rfc2898DeriveBytes(String, Int32) Rfc2898DeriveBytes(String, Int32) Rfc2898DeriveBytes(String, Int32)

Initializes a new instance of the Rfc2898DeriveBytes class using the password and salt size to derive the key.

Rfc2898DeriveBytes(String, Int32, Int32) Rfc2898DeriveBytes(String, Int32, Int32) Rfc2898DeriveBytes(String, Int32, Int32) Rfc2898DeriveBytes(String, Int32, Int32)

Initializes a new instance of the Rfc2898DeriveBytes class using a password, a salt size, and number of iterations to derive the key.

Rfc2898DeriveBytes(String, Int32, Int32, HashAlgorithmName) Rfc2898DeriveBytes(String, Int32, Int32, HashAlgorithmName) Rfc2898DeriveBytes(String, Int32, Int32, HashAlgorithmName) Rfc2898DeriveBytes(String, Int32, Int32, HashAlgorithmName)

Initializes a new instance of the Rfc2898DeriveBytes class using the specified password, salt size, number of iterations and the hash algorithm name to derive the key.

Properties

HashAlgorithm HashAlgorithm HashAlgorithm HashAlgorithm
IterationCount IterationCount IterationCount IterationCount

Gets or sets the number of iterations for the operation.

Salt Salt Salt Salt

Gets or sets the key salt value for the operation.

Methods

CryptDeriveKey(String, String, Int32, Byte[]) CryptDeriveKey(String, String, Int32, Byte[]) CryptDeriveKey(String, String, Int32, Byte[]) CryptDeriveKey(String, String, Int32, Byte[])

Derives a cryptographic key from the Rfc2898DeriveBytes object.

Dispose() Dispose() Dispose() Dispose()

When overridden in a derived class, releases all resources used by the current instance of the DeriveBytes class.

(Inherited from DeriveBytes)
Dispose(Boolean) Dispose(Boolean) Dispose(Boolean) Dispose(Boolean)

Releases the unmanaged resources used by the Rfc2898DeriveBytes class and optionally releases the managed resources.

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetBytes(Int32) GetBytes(Int32) GetBytes(Int32) GetBytes(Int32)

Returns the pseudo-random key for this object.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
Reset() Reset() Reset() Reset()

Resets the state of the operation.

ToString() ToString() ToString() ToString()

Returns a string that represents the current object.

(Inherited from Object)

Applies to

See Also