CryptoStream Class

Definition

public ref class CryptoStream : System::IO::Stream

public class CryptoStream : System.IO.Stream

[System.Runtime.InteropServices.ComVisible(true)]public class CryptoStream : System.IO.Stream

type CryptoStream = class    inherit Stream    interface IDisposable

[<System.Runtime.InteropServices.ComVisible(true)>]type CryptoStream = class    inherit Stream    interface IDisposable

Public Class CryptoStreamInherits Stream

Inheritance

Object

Stream

CryptoStream

Inheritance

Object

MarshalByRefObject

Stream

CryptoStream

Attributes

ComVisibleAttribute

Implements

IDisposable

Examples

The following example demonstrates how to use aCryptoStream to encrypt a string. This method uses theAes class with the specifiedKey and initialization vector (IV).

using System;using System.IO;using System.Security.Cryptography;class AesExample{    public static void Main()    {        try        {            string original = "Here is some data to encrypt!";            // Create a new instance of the Aes class.            // This generates a new key and initialization vector (IV).            using (Aes myAes = Aes.Create())            {                // Encrypt the string to an array of bytes.                byte[] encrypted = EncryptStringToBytes(original, myAes.Key, myAes.IV);                // Decrypt the bytes to a string.                string roundtrip = DecryptStringFromBytes(encrypted, myAes.Key, myAes.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(nameof(plainText));        if (Key == null || Key.Length <= 0)            throw new ArgumentNullException(nameof(Key));        if (IV == null || IV.Length <= 0)            throw new ArgumentNullException(nameof(IV));        byte[] encrypted;        // Create a Aes object with the specified key and IV.        using (Aes aesAlg = Aes.Create())        {            aesAlg.Key = Key;            aesAlg.IV = IV;            // Create an encryptor to perform the stream transform.            ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);            // Create the streams used for encryption.            using (MemoryStream msEncrypt = new())            {                using (CryptoStream csEncrypt = new(msEncrypt, encryptor, CryptoStreamMode.Write))                {                    using (StreamWriter swEncrypt = new(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(nameof(cipherText));        if (Key == null || Key.Length <= 0)            throw new ArgumentNullException(nameof(Key));        if (IV == null || IV.Length <= 0)            throw new ArgumentNullException(nameof(IV));        // Declare the string used to hold the decrypted text.        string plaintext = null;        // Create a Aes object with the specified key and IV.        using (Aes aesAlg = Aes.Create())        {            aesAlg.Key = Key;            aesAlg.IV = IV;            // Create a decryptor to perform the stream transform.            ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);            // Create the streams used for decryption.            using (MemoryStream msDecrypt = new(cipherText))            {                using (CryptoStream csDecrypt = new(msDecrypt, decryptor, CryptoStreamMode.Read))                {                    using (StreamReader srDecrypt = new(csDecrypt))                    {                        // Read the decrypted bytes from the decrypting stream                        // and place them in a string.                        plaintext = srDecrypt.ReadToEnd();                    }                }            }        }        return plaintext;    }}

Imports System.IOImports System.Security.CryptographyClass AesExample    Public Shared Sub Main()        Try            Dim original As String = "Here is some data to encrypt!"            ' Create a new instance of the Aes class.            ' This generates a new key and initialization vector (IV).            Using myAes = Aes.Create()                ' Encrypt the string to an array of bytes.                Dim encrypted As Byte() = EncryptStringToBytes(original, myAes.Key, myAes.IV)                ' Decrypt the bytes to a string.                Dim roundtrip As String = DecryptStringFromBytes(encrypted, myAes.Key, myAes.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    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(NameOf(plainText))        End If        If Key Is Nothing OrElse Key.Length <= 0 Then            Throw New ArgumentNullException(NameOf(Key))        End If        If IV Is Nothing OrElse IV.Length <= 0 Then            Throw New ArgumentNullException(NameOf(IV))        End If        Dim encrypted() As Byte        ' Create an Aes object with the specified key and IV.        Using aesAlg = Aes.Create()            aesAlg.Key = Key            aesAlg.IV = IV            ' Create an encryptor to perform the stream transform.            Dim encryptor As ICryptoTransform = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.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(NameOf(cipherText))        End If        If Key Is Nothing OrElse Key.Length <= 0 Then            Throw New ArgumentNullException(NameOf(Key))        End If        If IV Is Nothing OrElse IV.Length <= 0 Then            Throw New ArgumentNullException(NameOf(IV))        End If        ' Declare the string used to hold the decrypted text.        Dim plaintext As String = Nothing        ' Create an Aes object with the specified key and IV.        Using aesAlg = Aes.Create()            aesAlg.Key = Key            aesAlg.IV = IV            ' Create a decryptor to perform the stream transform.            Dim decryptor As ICryptoTransform = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.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 isCryptoStream. Any cryptographic objects that implementCryptoStream can be chained together with any objects that implementStream, 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 yourCryptoStream object after you're finished using it by calling theClear method. Doing so flushes the underlying stream and causes all remaining blocks of data to be processed by theCryptoStream object. However, if an exception occurs before you call theClose method, theCryptoStream object might not be closed. To ensure that theClose method always gets called, place your call to theClear method within thefinally block of atry/catch statement.

This type implements theIDisposable interface. When you've finished using the type, you should dispose of it either directly or indirectly by calling itsClear method, which in turn calls itsIDisposable implementation. To dispose of the type directly, call itsClear method in atry/catch block. To dispose of it indirectly, use a language construct such asusing (in C#) orUsing (in Visual Basic).

See also

• Cryptographic Services
• Partial and zero-byte reads in DeflateStream, GZipStream, and CryptoStream