PasswordDeriveBytes-Klasse

Artikel
08/20/2007

Leitet mithilfe einer Erweiterung des PBKDF1-Algorithmus einen Schlüssel von einem Kennwort ab.

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

Syntax

'Declaration
<ComVisibleAttribute(True)> _
Public Class PasswordDeriveBytes
    Inherits DeriveBytes
'Usage
Dim instance As PasswordDeriveBytes

[ComVisibleAttribute(true)] 
public class PasswordDeriveBytes : DeriveBytes

[ComVisibleAttribute(true)] 
public ref class PasswordDeriveBytes : public DeriveBytes

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

ComVisibleAttribute(true) 
public class PasswordDeriveBytes extends DeriveBytes

Hinweise

Diese Klasse verwendet eine Erweiterung des PBKDF1-Algorithmus (definiert im PKCS#5-Standard, Version 2.0) für das Ableiten von Bytes aus einem Kennwort, die als Schlüsselinformationen geeignet sind. Der Standard wird in IETF RRC 2898 dokumentiert.

Sicherheitshinweis
Schreiben Sie unter keinen Umständen Kennwörter in den Quellcode. Kennwörter mit vordefiniertem Code können mithilfe des MSIL Disassembler-Tool (Ildasm.exe)-Tools, einem Hex-Editor, oder durch das Öffnen der Assembly in einem Text-Editor (z. B. Editor.exe) abgerufen werden.

Beispiel

Im folgenden Codebeispiel wird mithilfe der PasswordDeriveBytes-Klasse ein Schlüssel aus einem Kennwort erstellt.

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:")

        '********************************************************
        '* Security Note: Never hard-code a password within your
        '* source code.  Hard-coded passwords can be retrieved 
        '* from a compiled assembly.
        '********************************************************
        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 add it to the Key property.
            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:");

        //********************************************************
        //* Security Note: Never hard-code a password within your
        //* source code.  Hard-coded passwords can be retrieved 
        //* from a compiled assembly.
        //********************************************************

        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 add it to the Key property.
            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 - 1; 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 add it to the Key property.
        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();
}

Vererbungshierarchie

System.Object
System.Security.Cryptography.DeriveBytes
System.Security.Cryptography.PasswordDeriveBytes

Threadsicherheit

Alle öffentlichen statischen (Shared in Visual Basic) Member dieses Typs sind threadsicher. Bei Instanzmembern ist die Threadsicherheit nicht gewährleistet.

Plattformen

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

.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.

Freigeben über

PasswordDeriveBytes-Klasse

Syntax

Hinweise

Beispiel

Vererbungshierarchie

Threadsicherheit

Plattformen

Versionsinformationen

.NET Framework

Siehe auch

Referenz

Weitere Ressourcen

Zusätzliche Ressourcen