CryptoStream-Klasse
Definiert einen Stream, der Datenstreams mit kryptografischen Transformationen verbindet.
Namespace: System.Security.Cryptography
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
<ComVisibleAttribute(True)> _
Public Class CryptoStream
Inherits Stream
Implements IDisposable
'Usage
Dim instance As CryptoStream
[ComVisibleAttribute(true)]
public class CryptoStream : Stream, IDisposable
[ComVisibleAttribute(true)]
public ref class CryptoStream : public Stream, IDisposable
/** @attribute ComVisibleAttribute(true) */
public class CryptoStream extends Stream implements IDisposable
ComVisibleAttribute(true)
public class CryptoStream extends Stream implements IDisposable
Hinweise
Die Common Language Runtime verwendet einen streamorientierten Kryptografieentwurf. Der Kern dieses Entwurfs ist CryptoStream. Alle kryptografischen Objekte, die CryptoStream implementieren, können mit allen Objekten verkettet werden, die Stream implementieren, sodass der Ausgabestream eines Objekts als Eingabestream für ein anderes Objekt verwendet werden kann. Das Zwischenergebnis (die Ausgabe des ersten Objekts) muss nicht getrennt gespeichert werden.
Das CryptoStream-Objekt muss nach der Verwendung immer explizit geschlossen werden, indem die Close-Methode aufgerufen wird. Dadurch wird der Stream entleert, und alle übrigen Datenblöcke werden vom CryptoStream-Objekt verarbeitet. Wenn jedoch vor dem Aufrufen der Close-Methode eine Ausnahme auftritt, kann das CryptoStream-Objekt möglicherweise nicht geschlossen werden. Um sicherzustellen, dass die Close-Methode immer aufgerufen wird, rufen Sie die Close-Methode im finally-Block einer try/catch-Anweisung auf.
Beispiel
Im folgenden Beispiel wird das Verschlüsseln einer Zeichenfolge mit einem CryptoStream veranschaulicht. Diese Methode verwendet die RijndaelManaged-Klasse mit dem angegebenen Key und dem angegebenen Initialisierungsvektor (IV).
Imports System.Security.Cryptography
Imports System.Text
Imports System.IO
Module RijndaelSample
Sub Main()
Try
' Create a new Rijndael object to generate a key
' and initialization vector (IV).
Dim RijndaelAlg As Rijndael = Rijndael.Create
' Create a string to encrypt.
Dim sData As String = "Here is some data to encrypt."
Dim FileName As String = "CText.txt"
' Encrypt text to a file using the file name, key, and IV.
EncryptTextToFile(sData, FileName, RijndaelAlg.Key, RijndaelAlg.IV)
' Decrypt the text from a file using the file name, key, and IV.
Dim Final As String = DecryptTextFromFile(FileName, RijndaelAlg.Key, RijndaelAlg.IV)
' Display the decrypted string to the console.
Console.WriteLine(Final)
Catch e As Exception
Console.WriteLine(e.Message)
End Try
Console.ReadLine()
End Sub
Sub EncryptTextToFile(ByVal Data As String, ByVal FileName As String, ByVal Key() As Byte, ByVal IV() As Byte)
Try
' Create or open the specified file.
Dim fStream As FileStream = File.Open(FileName, FileMode.OpenOrCreate)
' Create a new Rijndael object.
Dim RijndaelAlg As Rijndael = Rijndael.Create
' Create a CryptoStream using the FileStream
' and the passed key and initialization vector (IV).
Dim cStream As New CryptoStream(fStream, _
RijndaelAlg.CreateEncryptor(Key, IV), _
CryptoStreamMode.Write)
' Create a StreamWriter using the CryptoStream.
Dim sWriter As New StreamWriter(cStream)
Try
' Write the data to the stream
' to encrypt it.
sWriter.WriteLine(Data)
Catch e As Exception
Console.WriteLine("An error occurred: {0}", e.Message)
Finally
' Close the streams and
' close the file.
sWriter.Close()
cStream.Close()
fStream.Close()
End Try
Catch e As CryptographicException
Console.WriteLine("A Cryptographic error occurred: {0}", e.Message)
Catch e As UnauthorizedAccessException
Console.WriteLine("A file error occurred: {0}", e.Message)
End Try
End Sub
Function DecryptTextFromFile(ByVal FileName As String, ByVal Key() As Byte, ByVal IV() As Byte) As String
Try
' Create or open the specified file.
Dim fStream As FileStream = File.Open(FileName, FileMode.OpenOrCreate)
' Create a new Rijndael object.
Dim RijndaelAlg As Rijndael = Rijndael.Create
' Create a CryptoStream using the FileStream
' and the passed key and initialization vector (IV).
Dim cStream As New CryptoStream(fStream, _
RijndaelAlg.CreateDecryptor(Key, IV), _
CryptoStreamMode.Read)
' Create a StreamReader using the CryptoStream.
Dim sReader As New StreamReader(cStream)
' Read the data from the stream
' to decrypt it.
Dim val As String = Nothing
Try
val = sReader.ReadLine()
Catch e As Exception
Console.WriteLine("An Cerror occurred: {0}", e.Message)
Finally
' Close the streams and
' close the file.
sReader.Close()
cStream.Close()
fStream.Close()
End Try
' Return the string.
Return val
Catch e As CryptographicException
Console.WriteLine("A Cryptographic error occurred: {0}", e.Message)
Return Nothing
Catch e As UnauthorizedAccessException
Console.WriteLine("A file error occurred: {0}", e.Message)
Return Nothing
End Try
End Function
End Module
using System;
using System.Security.Cryptography;
using System.Text;
using System.IO;
class RijndaelSample
{
static void Main()
{
try
{
// Create a new Rijndael object to generate a key
// and initialization vector (IV).
Rijndael RijndaelAlg = Rijndael.Create();
// Create a string to encrypt.
string sData = "Here is some data to encrypt.";
string FileName = "CText.txt";
// Encrypt text to a file using the file name, key, and IV.
EncryptTextToFile(sData, FileName, RijndaelAlg.Key, RijndaelAlg.IV);
// Decrypt the text from a file using the file name, key, and IV.
string Final = DecryptTextFromFile(FileName, RijndaelAlg.Key, RijndaelAlg.IV);
// Display the decrypted string to the console.
Console.WriteLine(Final);
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
Console.ReadLine();
}
public static void EncryptTextToFile(String Data, String FileName, byte[] Key, byte[] IV)
{
try
{
// Create or open the specified file.
FileStream fStream = File.Open(FileName, FileMode.OpenOrCreate);
// Create a new Rijndael object.
Rijndael RijndaelAlg = Rijndael.Create();
// Create a CryptoStream using the FileStream
// and the passed key and initialization vector (IV).
CryptoStream cStream = new CryptoStream(fStream,
RijndaelAlg.CreateEncryptor(Key, IV),
CryptoStreamMode.Write);
// Create a StreamWriter using the CryptoStream.
StreamWriter sWriter = new StreamWriter(cStream);
try
{
// Write the data to the stream
// to encrypt it.
sWriter.WriteLine(Data);
}
catch (Exception e)
{
Console.WriteLine("An error occurred: {0}", e.Message);
}
finally
{
// Close the streams and
// close the file.
sWriter.Close();
cStream.Close();
fStream.Close();
}
}
catch (CryptographicException e)
{
Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
}
catch (UnauthorizedAccessException e)
{
Console.WriteLine("A file error occurred: {0}", e.Message);
}
}
public static string DecryptTextFromFile(String FileName, byte[] Key, byte[] IV)
{
try
{
// Create or open the specified file.
FileStream fStream = File.Open(FileName, FileMode.OpenOrCreate);
// Create a new Rijndael object.
Rijndael RijndaelAlg = Rijndael.Create();
// Create a CryptoStream using the FileStream
// and the passed key and initialization vector (IV).
CryptoStream cStream = new CryptoStream(fStream,
RijndaelAlg.CreateDecryptor(Key, IV),
CryptoStreamMode.Read);
// Create a StreamReader using the CryptoStream.
StreamReader sReader = new StreamReader(cStream);
string val = null;
try
{
// Read the data from the stream
// to decrypt it.
val = sReader.ReadLine();
}
catch (Exception e)
{
Console.WriteLine("An error occurred: {0}", e.Message);
}
finally
{
// Close the streams and
// close the file.
sReader.Close();
cStream.Close();
fStream.Close();
}
// Return the string.
return val;
}
catch (CryptographicException e)
{
Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
return null;
}
catch (UnauthorizedAccessException e)
{
Console.WriteLine("A file error occurred: {0}", e.Message);
return null;
}
}
}
Vererbungshierarchie
System.Object
System.MarshalByRefObject
System.IO.Stream
System.Security.Cryptography.CryptoStream
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 CE, Windows Millennium Edition, Windows Mobile für Pocket PC, Windows Mobile für Smartphone, 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.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0
.NET Compact Framework
Unterstützt in: 2.0
Siehe auch
Referenz
CryptoStream-Member
System.Security.Cryptography-Namespace