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CryptoStream Class

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Defines a stream that links data streams to cryptographic transformations.

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

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

public class CryptoStream : Stream, 
	IDisposable

The CryptoStream type exposes the following members.

  NameDescription
Public methodCryptoStreamInitializes 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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  NameDescription
Public propertyCanReadGets a value indicating whether the current CryptoStream is readable. (Overrides Stream.CanRead.)
Public propertyCanSeekGets a value indicating whether you can seek within the current CryptoStream. (Overrides Stream.CanSeek.)
Public propertyCanTimeoutGets a value that determines whether the current stream can time out. (Inherited from Stream.)
Public propertyCanWriteGets a value indicating whether the current CryptoStream is writable. (Overrides Stream.CanWrite.)
Public propertyLengthGets the length, in bytes, of the stream. (Overrides Stream.Length.)
Public propertyPositionGets or sets the position within the current stream. (Overrides Stream.Position.)
Public propertyReadTimeoutGets or sets a value, in miliseconds, that determines how long the stream will attempt to read before timing out. (Inherited from Stream.)
Public propertyWriteTimeoutGets 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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  NameDescription
Public methodBeginReadBegins an asynchronous read operation. (Inherited from Stream.)
Public methodBeginWriteBegins an asynchronous write operation. (Inherited from Stream.)
Public methodClearReleases all resources used by the CryptoStream.
Public methodCloseCloses the current stream and releases any resources (such as sockets and file handles) associated with the current stream. (Inherited from Stream.)
Public methodCopyTo(Stream)Reads all the bytes from the current stream and writes them to the destination stream. (Inherited from Stream.)
Public methodCopyTo(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 methodCopyToAsync(Stream)Asynchronously reads the bytes from the current stream and writes them to another stream. (Inherited from Stream.)
Public methodCopyToAsync(Stream, Int32)Asynchronously reads the bytes from the current stream and writes them to another stream, using a specified buffer size. (Inherited from Stream.)
Public methodCopyToAsync(Stream, Int32, CancellationToken)Asynchronously reads the bytes from the current stream and writes them to another stream, using a specified buffer size and cancellation token. (Inherited from Stream.)
Public methodDispose()Releases all resources used by the Stream. (Inherited from Stream.)
Protected methodDispose(Boolean)Releases the unmanaged resources used by the CryptoStream and optionally releases the managed resources. (Overrides Stream.Dispose(Boolean).)
Public methodEndReadWaits for the pending asynchronous read to complete. (Inherited from Stream.)
Public methodEndWriteEnds an asynchronous write operation. (Inherited from Stream.)
Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodFlushClears all buffers for this stream and causes any buffered data to be written to the underlying device. (Overrides Stream.Flush().)
Public methodFlushAsync()Asynchronously clears all buffers for this stream and causes any buffered data to be written to the underlying device. (Inherited from Stream.)
Public methodFlushAsync(CancellationToken)Asynchronously clears all buffers for this stream, causes any buffered data to be written to the underlying device, and monitors cancellation requests. (Inherited from Stream.)
Public methodFlushFinalBlockUpdates the underlying data source or repository with the current state of the buffer, and then clears the buffer.
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodReadReads a sequence of bytes from the current CryptoStream and advances the position within the stream by the number of bytes read. (Overrides Stream.Read(Byte[], Int32, Int32).)
Public methodReadAsync(Byte[], Int32, Int32)Asynchronously reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read. (Inherited from Stream.)
Public methodReadAsync(Byte[], Int32, Int32, CancellationToken)Asynchronously reads a sequence of bytes from the current stream, advances the position within the stream by the number of bytes read, and monitors cancellation requests. (Inherited from Stream.)
Public methodReadByteReads 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 methodSeekThrows a NotSupportedException in all cases. (Overrides Stream.Seek(Int64, SeekOrigin).)
Public methodSetLengthThrows a NotSupportedException in all cases. (Overrides Stream.SetLength(Int64).)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Public methodWriteWrites 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(Byte[], Int32, Int32).)
Public methodWriteAsync(Byte[], Int32, Int32)Asynchronously writes a sequence of bytes to the current stream and advances the current position within this stream by the number of bytes written. (Inherited from Stream.)
Public methodWriteAsync(Byte[], Int32, Int32, CancellationToken)Asynchronously writes a sequence of bytes to the current stream, advances the current position within this stream by the number of bytes written, and monitors cancellation requests. (Inherited from Stream.)
Public methodWriteByteWrites 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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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.

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.


static string DecryptStringFromBytes_Aes(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("Key");

    // Declare the string used to hold
    // the decrypted text.
    string plaintext = null;

    // Create an AesManaged object
    // with the specified key and IV.
    using (AesManaged aesAlg = new AesManaged())
    {
        aesAlg.Key = Key;
        aesAlg.IV = IV;

        // Create a decrytor to perform the stream transform.
        ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.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;

}


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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

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