• Article

CryptoStream Class

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Defines a stream that links data streams to cryptographic transformations.

Inheritance Hierarchy

System.Object
  System.IO.Stream
    System.Security.Cryptography.CryptoStream

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

Syntax

'Declaration
<ComVisibleAttribute(True)> _
Public Class CryptoStream _
    Inherits Stream _
    Implements IDisposable

[ComVisibleAttribute(true)]
public class CryptoStream : Stream, 
    IDisposable

The CryptoStream type exposes the following members.

Constructors

  Name Description
Public methodSupported by Silverlight for Windows Phone CryptoStream Initializes a new instance of the CryptoStream class with a target data stream, the transformation to use, and the mode of the stream.

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Properties

  Name Description
Public propertySupported by Silverlight for Windows Phone CanRead Gets a value indicating whether the current CryptoStream is readable. (Overrides Stream.CanRead.)
Public propertySupported by Silverlight for Windows Phone CanSeek Gets a value indicating whether you can seek within the current CryptoStream. (Overrides Stream.CanSeek.)
Public propertySupported by Silverlight for Windows Phone CanTimeout Gets a value that determines whether the current stream can time out. (Inherited from Stream.)
Public propertySupported by Silverlight for Windows Phone CanWrite Gets a value indicating whether the current CryptoStream is writable. (Overrides Stream.CanWrite.)
Public propertySupported by Silverlight for Windows Phone Length Gets the length, in bytes, of the stream. (Overrides Stream.Length.)
Public propertySupported by Silverlight for Windows Phone Position Gets or sets the position within the current stream. (Overrides Stream.Position.)
Public propertySupported by Silverlight for Windows Phone ReadTimeout Gets or sets a value, in miliseconds, that determines how long the stream will attempt to read before timing out. (Inherited from Stream.)
Public propertySupported by Silverlight for Windows Phone WriteTimeout Gets or sets a value, in miliseconds, that determines how long the stream will attempt to write before timing out. (Inherited from Stream.)

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Methods

  Name Description
Public methodSupported by Silverlight for Windows Phone BeginRead Begins an asynchronous read operation. (Inherited from Stream.)
Public methodSupported by Silverlight for Windows Phone BeginWrite Begins an asynchronous write operation. (Inherited from Stream.)
Public methodSupported by Silverlight for Windows Phone Clear Releases all resources used by the CryptoStream.
Public methodSupported by Silverlight for Windows Phone Close Closes the current stream and releases any resources (such as sockets and file handles) associated with the current stream. (Inherited from Stream.)
Public methodSupported by Silverlight for Windows Phone CopyTo(Stream) Reads all the bytes from the current stream and writes them to the destination stream. (Inherited from Stream.)
Public methodSupported by Silverlight for Windows Phone CopyTo(Stream, Int32) Reads all the bytes from the current stream and writes them to a destination stream, using a specified buffer size. (Inherited from Stream.)
Public methodSupported by Silverlight for Windows Phone Dispose() Releases all resources used by the Stream. (Inherited from Stream.)
Protected methodSupported by Silverlight for Windows Phone Dispose(Boolean) Releases the unmanaged resources used by the CryptoStream and optionally releases the managed resources. (Overrides Stream.Dispose(Boolean).)
Public methodSupported by Silverlight for Windows Phone EndRead Waits for the pending asynchronous read to complete. (Inherited from Stream.)
Public methodSupported by Silverlight for Windows Phone EndWrite Ends an asynchronous write operation. (Inherited from Stream.)
Public methodSupported by Silverlight for Windows Phone Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows Phone Finalize Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by Silverlight for Windows Phone Flush Clears all buffers for this stream and causes any buffered data to be written to the underlying device. (Overrides Stream.Flush().)
Public methodSupported by Silverlight for Windows Phone FlushFinalBlock Updates the underlying data source or repository with the current state of the buffer, and then clears the buffer.
Public methodSupported by Silverlight for Windows Phone GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public methodSupported by Silverlight for Windows Phone GetType Gets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows Phone MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by Silverlight for Windows Phone Read Reads a sequence of bytes from the current CryptoStream and advances the position within the stream by the number of bytes read. (Overrides Stream.Read(array<Byte[], Int32, Int32).)
Public methodSupported by Silverlight for Windows Phone ReadByte Reads a byte from the stream and advances the position within the stream by one byte, or returns -1 if at the end of the stream. (Inherited from Stream.)
Public methodSupported by Silverlight for Windows Phone Seek Throws a NotSupportedException in all cases. (Overrides Stream.Seek(Int64, SeekOrigin).)
Public methodSupported by Silverlight for Windows Phone SetLength Throws a NotSupportedException in all cases. (Overrides Stream.SetLength(Int64).)
Public methodSupported by Silverlight for Windows Phone ToString Returns a string that represents the current object. (Inherited from Object.)
Public methodSupported by Silverlight for Windows Phone Write Writes a sequence of bytes to the current CryptoStream and advances the current position within this stream by the number of bytes written. (Overrides Stream.Write(array<Byte[], Int32, Int32).)
Public methodSupported by Silverlight for Windows Phone WriteByte Writes a byte to the current position in the stream and advances the position within the stream by one byte. (Inherited from Stream.)

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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.

You should always explicitly close your CryptoStream object after you are done using it by calling the Close method. Doing so flushes the 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 Close method within the finally block of a try/catch statement.

Examples

The following example demonstrates how to use the CryptoStream class when you encrypt an isolated storage file. This code example is part of a larger example provided for the AesManaged class.

Using aes = New System.Security.Cryptography.AesManaged()
    Dim deriveBytes As New Rfc2898DeriveBytes(passwordBox.Password, Encoding.UTF8.GetBytes(PasswordSalt))
    aes.Key = deriveBytes.GetBytes(128 / 8)
    If Integer.MaxValue = Int64.MaxValue Then intSize = 8
    isoStoreStream.Write(BitConverter.GetBytes(aes.IV.Length), 0, intSize)
    isoStoreStream.Write(aes.IV, 0, aes.IV.Length)
    Using cs As New CryptoStream(isoStoreStream, aes.CreateEncryptor(), CryptoStreamMode.Write)
        Dim rawPlaintext As Byte() = Encoding.Unicode.GetBytes(inputBox.Text)
        cs.Write(rawPlaintext, 0, rawPlaintext.Length)
        cs.FlushFinalBlock()
    End Using
End Using

using (Aes aes = new AesManaged())
{
    Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes(passwordBox.Password, Encoding.UTF8.GetBytes(PasswordSalt));
    aes.Key = deriveBytes.GetBytes(128 / 8);
    isoStoreStream.Write(BitConverter.GetBytes(aes.IV.Length), 0, sizeof(int));
    isoStoreStream.Write(aes.IV, 0, aes.IV.Length);

    using (CryptoStream cs = new CryptoStream(isoStoreStream, aes.CreateEncryptor(), CryptoStreamMode.Write))
    {
        byte[] rawPlaintext = Encoding.Unicode.GetBytes(inputBox.Text);
        cs.Write(rawPlaintext, 0, rawPlaintext.Length);
        cs.FlushFinalBlock();
    }
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.