CryptoStream
Class
Definition
Defines a stream that links data streams to cryptographic transformations.
[System.Runtime.InteropServices.ComVisible(true)]
public class CryptoStream : System.IO.Stream
- Inheritance
- Attributes
Inherited Members
System.IO.Stream
System.MarshalByRefObject
System.Object
Examples
The following example demonstrates how to use a CryptoStream to encrypt a string. This method uses RijndaelManaged class with the specified Key and initialization vector (IV).
using System;
using System.IO;
using System.Security.Cryptography;
namespace RijndaelManaged_Example
{
class RijndaelExample
{
public static void Main()
{
try
{
string original = "Here is some data to encrypt!";
// Create a new instance of the Rijndael
// class. This generates a new key and initialization
// vector (IV).
using (Rijndael myRijndael = Rijndael.Create())
{
// Encrypt the string to an array of bytes.
byte[] encrypted = EncryptStringToBytes(original, myRijndael.Key, myRijndael.IV);
// Decrypt the bytes to a string.
string roundtrip = DecryptStringFromBytes(encrypted, myRijndael.Key, myRijndael.IV);
//Display the original data and the decrypted data.
Console.WriteLine("Original: {0}", original);
Console.WriteLine("Round Trip: {0}", roundtrip);
}
}
catch (Exception e)
{
Console.WriteLine("Error: {0}", e.Message);
}
}
static byte[] EncryptStringToBytes(string plainText, byte[] Key, byte[] IV)
{
// Check arguments.
if (plainText == null || plainText.Length <= 0)
throw new ArgumentNullException("plainText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
if (IV == null || IV.Length <= 0)
throw new ArgumentNullException("IV");
byte[] encrypted;
// Create an Rijndael object
// with the specified key and IV.
using (Rijndael rijAlg = Rijndael.Create())
{
rijAlg.Key = Key;
rijAlg.IV = IV;
// Create an encryptor to perform the stream transform.
ICryptoTransform encryptor = rijAlg.CreateEncryptor(rijAlg.Key, rijAlg.IV);
// Create the streams used for encryption.
using (MemoryStream msEncrypt = new MemoryStream())
{
using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
{
//Write all data to the stream.
swEncrypt.Write(plainText);
}
encrypted = msEncrypt.ToArray();
}
}
}
// Return the encrypted bytes from the memory stream.
return encrypted;
}
static string DecryptStringFromBytes(byte[] cipherText, byte[] Key, byte[] IV)
{
// Check arguments.
if (cipherText == null || cipherText.Length <= 0)
throw new ArgumentNullException("cipherText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
if (IV == null || IV.Length <= 0)
throw new ArgumentNullException("IV");
// Declare the string used to hold
// the decrypted text.
string plaintext = null;
// Create an Rijndael object
// with the specified key and IV.
using (Rijndael rijAlg = Rijndael.Create())
{
rijAlg.Key = Key;
rijAlg.IV = IV;
// Create a decryptor to perform the stream transform.
ICryptoTransform decryptor = rijAlg.CreateDecryptor(rijAlg.Key, rijAlg.IV);
// Create the streams used for decryption.
using (MemoryStream msDecrypt = new MemoryStream(cipherText))
{
using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
{
using (StreamReader srDecrypt = new StreamReader(csDecrypt))
{
// Read the decrypted bytes from the decrypting stream
// and place them in a string.
plaintext = srDecrypt.ReadToEnd();
}
}
}
}
return plaintext;
}
}
}
Imports System
Imports System.IO
Imports System.Security.Cryptography
Class RijndaelExample
Public Shared Sub Main()
Try
Dim original As String = "Here is some data to encrypt!"
' Create a new instance of the Rijndael
' class. This generates a new key and initialization
' vector (IV).
Using myRijndael = Rijndael.Create()
' Encrypt the string to an array of bytes.
Dim encrypted As Byte() = EncryptStringToBytes(original, myRijndael.Key, myRijndael.IV)
' Decrypt the bytes to a string.
Dim roundtrip As String = DecryptStringFromBytes(encrypted, myRijndael.Key, myRijndael.IV)
'Display the original data and the decrypted data.
Console.WriteLine("Original: {0}", original)
Console.WriteLine("Round Trip: {0}", roundtrip)
End Using
Catch e As Exception
Console.WriteLine("Error: {0}", e.Message)
End Try
End Sub 'Main
Shared Function EncryptStringToBytes(ByVal plainText As String, ByVal Key() As Byte, ByVal IV() As Byte) As Byte()
' Check arguments.
If plainText Is Nothing OrElse plainText.Length <= 0 Then
Throw New ArgumentNullException("plainText")
End If
If Key Is Nothing OrElse Key.Length <= 0 Then
Throw New ArgumentNullException("Key")
End If
If IV Is Nothing OrElse IV.Length <= 0 Then
Throw New ArgumentNullException("IV")
End If
Dim encrypted() As Byte
' Create an Rijndael object
' with the specified key and IV.
Using rijAlg = Rijndael.Create()
rijAlg.Key = Key
rijAlg.IV = IV
' Create an encryptor to perform the stream transform.
Dim encryptor As ICryptoTransform = rijAlg.CreateEncryptor(rijAlg.Key, rijAlg.IV)
' Create the streams used for encryption.
Using msEncrypt As New MemoryStream()
Using csEncrypt As New CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write)
Using swEncrypt As New StreamWriter(csEncrypt)
'Write all data to the stream.
swEncrypt.Write(plainText)
End Using
encrypted = msEncrypt.ToArray()
End Using
End Using
End Using
' Return the encrypted bytes from the memory stream.
Return encrypted
End Function 'EncryptStringToBytes
Shared Function DecryptStringFromBytes(ByVal cipherText() As Byte, ByVal Key() As Byte, ByVal IV() As Byte) As String
' Check arguments.
If cipherText Is Nothing OrElse cipherText.Length <= 0 Then
Throw New ArgumentNullException("cipherText")
End If
If Key Is Nothing OrElse Key.Length <= 0 Then
Throw New ArgumentNullException("Key")
End If
If IV Is Nothing OrElse IV.Length <= 0 Then
Throw New ArgumentNullException("IV")
End If
' Declare the string used to hold
' the decrypted text.
Dim plaintext As String = Nothing
' Create an Rijndael object
' with the specified key and IV.
Using rijAlg = Rijndael.Create()
rijAlg.Key = Key
rijAlg.IV = IV
' Create a decryptor to perform the stream transform.
Dim decryptor As ICryptoTransform = rijAlg.CreateDecryptor(rijAlg.Key, rijAlg.IV)
' Create the streams used for decryption.
Using msDecrypt As New MemoryStream(cipherText)
Using csDecrypt As New CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read)
Using srDecrypt As New StreamReader(csDecrypt)
' Read the decrypted bytes from the decrypting stream
' and place them in a string.
plaintext = srDecrypt.ReadToEnd()
End Using
End Using
End Using
End Using
Return plaintext
End Function 'DecryptStringFromBytes
End Class
Remarks
The common language runtime uses a stream-oriented design for cryptography. The core of this design is CryptoStream. Any cryptographic objects that implement CryptoStream can be chained together with any objects that implement Stream, so the streamed output from one object can be fed into the input of another object. The intermediate result (the output from the first object) does not need to be stored separately.
Important
This type implements the IDisposable interface. When you have finished using the type, you should dispose of it either directly or indirectly by calling its Clear method, which in turn calls its IDisposable implementation. To dispose of the type directly, call its Clear method in a try/catch block. To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). For more information, see the "Using an Object that Implements IDisposable" section in the IDisposable interface topic.
You should always explicitly close your CryptoStream object after you are done using it by calling the Clear method. Doing so flushes the underlying stream and causes all remaining blocks of data to be processed by the CryptoStream object. However, if an exception occurs before you call the Close method, the CryptoStream object might not be closed. To ensure that the Close method always gets called, place your call to the Clear method within the finally block of a try/catch statement.
Constructors
| CryptoStream(Stream, ICryptoTransform, CryptoStreamMode) |
Initializes a new instance of the CryptoStream class with a target data stream, the transformation to use, and the mode of the stream. |
| CryptoStream(Stream, ICryptoTransform, CryptoStreamMode, Boolean) | |
Properties
| CanRead |
Gets a value indicating whether the current CryptoStream is readable. |
| CanSeek |
Gets a value indicating whether you can seek within the current CryptoStream. |
| CanWrite |
Gets a value indicating whether the current CryptoStream is writable. |
| HasFlushedFinalBlock |
Gets a value indicating whether the final buffer block has been written to the underlying stream. |
| Length |
Gets the length in bytes of the stream. |
| Position |
Gets or sets the position within the current stream. |
Methods
| Clear() |
Releases all resources used by the CryptoStream. |
| Dispose(Boolean) |
Releases the unmanaged resources used by the CryptoStream and optionally releases the managed resources. |
| Flush() |
Clears all buffers for the current stream and causes any buffered data to be written to the underlying device. |
| FlushAsync(CancellationToken) |
Clears all buffers for the current stream asynchronously, causes any buffered data to be written to the underlying device, and monitors cancellation requests. |
| FlushFinalBlock() |
Updates the underlying data source or repository with the current state of the buffer, then clears the buffer. |
| Read(Byte[], Int32, Int32) |
Reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read. |
| ReadAsync(Byte[], Int32, Int32, CancellationToken) |
Reads a sequence of bytes from the current stream asynchronously, advances the position within the stream by the number of bytes read, and monitors cancellation requests. |
| ReadByte() | |
| Seek(Int64, SeekOrigin) |
Sets the position within the current stream. |
| SetLength(Int64) |
Sets the length of the current stream. |
| Write(Byte[], Int32, Int32) |
Writes a sequence of bytes to the current CryptoStream and advances the current position within the stream by the number of bytes written. |
| WriteAsync(Byte[], Int32, Int32, CancellationToken) |
Writes a sequence of bytes to the current stream asynchronously, advances the current position within the stream by the number of bytes written, and monitors cancellation requests. |
| WriteByte(Byte) | |