CryptoStream Class
Defines a stream that links data streams to cryptographic transformations.
Assembly: mscorlib (in mscorlib.dll)
The CryptoStream type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | CryptoStream | Initializes a new instance of the CryptoStream class with a target data stream, the transformation to use, and the mode of the stream. |
| Name | Description | |
|---|---|---|
![]() | CanRead | Gets a value indicating whether the current CryptoStream is readable. (Overrides Stream.CanRead.) |
![]() | CanSeek | Gets a value indicating whether you can seek within the current CryptoStream. (Overrides Stream.CanSeek.) |
![]() | CanTimeout | Gets a value that determines whether the current stream can time out. (Inherited from Stream.) |
![]() | CanWrite | Gets a value indicating whether the current CryptoStream is writable. (Overrides Stream.CanWrite.) |
![]() | 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. (Overrides Stream.Length.) |
![]() | Position | Gets or sets the position within the current stream. (Overrides Stream.Position.) |
![]() | ReadTimeout | Gets or sets a value, in miliseconds, that determines how long the stream will attempt to read before timing out. (Inherited from Stream.) |
![]() | WriteTimeout | Gets or sets a value, in miliseconds, that determines how long the stream will attempt to write before timing out. (Inherited from Stream.) |
| Name | Description | |
|---|---|---|
![]() | BeginRead | Begins an asynchronous read operation. (Inherited from Stream.) |
![]() | BeginWrite | Begins an asynchronous write operation. (Inherited from Stream.) |
![]() | Clear | Releases all resources used by the CryptoStream. |
![]() | Close | Closes the current stream and releases any resources (such as sockets and file handles) associated with the current stream. (Inherited from Stream.) |
![]() | CopyTo(Stream) | Reads the bytes from the current stream and writes them to the destination stream. (Inherited from Stream.) |
![]() | 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.) |
![]() | CreateObjRef | Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object. (Inherited from MarshalByRefObject.) |
![]() | CreateWaitHandle | Obsolete. Allocates a WaitHandle object. (Inherited from Stream.) |
![]() | Dispose | Releases all resources used by the Stream. (Inherited from Stream.) |
![]() | Dispose(Boolean) | Releases the unmanaged resources used by the CryptoStream and optionally releases the managed resources. (Overrides Stream.Dispose(Boolean).) |
![]() | EndRead | Waits for the pending asynchronous read to complete. (Inherited from Stream.) |
![]() | EndWrite | Ends an asynchronous write operation. (Inherited from Stream.) |
![]() | Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
![]() | Flush | Clears all buffers for this stream and causes any buffered data to be written to the underlying device. (Overrides Stream.Flush.) |
![]() | FlushFinalBlock | Updates the underlying data source or repository with the current state of the buffer, then clears the buffer. |
![]() | GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
![]() | GetLifetimeService | Retrieves the current lifetime service object that controls the lifetime policy for this instance. (Inherited from MarshalByRefObject.) |
![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() | InitializeLifetimeService | Obtains a lifetime service object to control the lifetime policy for this instance. (Inherited from MarshalByRefObject.) |
![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() | MemberwiseClone(Boolean) | Creates a shallow copy of the current MarshalByRefObject object. (Inherited from MarshalByRefObject.) |
![]() | ObjectInvariant | Infrastructure. Provides support for a Contract. (Inherited from Stream.) |
![]() | 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(Byte(), Int32, Int32).) |
![]() | 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.) |
![]() | Seek | Sets the position within the current stream. (Overrides Stream.Seek(Int64, SeekOrigin).) |
![]() | SetLength | Sets the length of the current stream. (Overrides Stream.SetLength(Int64).) |
![]() | ToString | Returns a string that represents the current object. (Inherited from Object.) |
![]() | 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(Byte(), Int32, Int32).) |
![]() | WriteByte | Writes a byte to the current position in the stream and advances the position within the stream by one byte. (Inherited from Stream.) |
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 remain 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 a CryptoStream to encrypt a string. This method uses RijndaelManaged class with the specified Key and initialization vector (IV).
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("Key") 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 a decrytor 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("Key") 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 decrytor 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
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
