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TripleDESCryptoServiceProvider.CreateDecryptor Method (Byte[], Byte[])

Creates a symmetric TripleDES decryptor object with the specified key (Key) and initialization vector (IV).

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

public override ICryptoTransform CreateDecryptor(
	byte[] rgbKey,
	byte[] rgbIV
)

Parameters

rgbKey
Type: System.Byte[]

The secret key to use for the symmetric algorithm.

rgbIV
Type: System.Byte[]

The initialization vector to use for the symmetric algorithm.

Return Value

Type: System.Security.Cryptography.ICryptoTransform
A symmetric TripleDES decryptor object.

ExceptionCondition
CryptographicException

The value of the Mode property is OFB.

-or-

The value of the Mode property is CFB and the value of the FeedbackSize property is not 8.

-or-

An invalid key size was used.

-or-

The algorithm key size was not available.

This method decrypts an encrypted message created using the CreateEncryptor overload with the same parameters.

The following code example creates a TripleDESCryptoServiceProvider object and uses it to encrypt and decrypt data in a file.

using System;
using System.Security.Cryptography;
using System.Text;
using System.IO;

class TrippleDESCSPSample
{

    static void Main()
    {
        try
        {
            // Create a new TripleDESCryptoServiceProvider object 
            // to generate a key and initialization vector (IV).
            TripleDESCryptoServiceProvider tDESalg = new TripleDESCryptoServiceProvider();

            // Create a string to encrypt. 
            string sData = "Here is some data to encrypt.";
            string FileName = "CText.txt";

            // Encrypt text to a file using the file name, key, and IV.
            EncryptTextToFile(sData, FileName, tDESalg.Key, tDESalg.IV);

            // Decrypt the text from a file using the file name, key, and IV. 
            string Final = DecryptTextFromFile(FileName, tDESalg.Key, tDESalg.IV);

            // Display the decrypted string to the console.
            Console.WriteLine(Final);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
        }

    }

    public static void EncryptTextToFile(String Data, String FileName, byte[] Key, byte[] IV)
    {
        try
        {
            // Create or open the specified file.
            FileStream fStream = File.Open(FileName,FileMode.OpenOrCreate);

            // Create a CryptoStream using the FileStream  
            // and the passed key and initialization vector (IV).
            CryptoStream cStream = new CryptoStream(fStream, 
                new TripleDESCryptoServiceProvider().CreateEncryptor(Key,IV), 
                CryptoStreamMode.Write); 

            // Create a StreamWriter using the CryptoStream.
            StreamWriter sWriter = new StreamWriter(cStream);

            // Write the data to the stream  
            // to encrypt it.
            sWriter.WriteLine(Data);

            // Close the streams and 
            // close the file.
            sWriter.Close();
            cStream.Close();
            fStream.Close();
        }
        catch(CryptographicException e)
        {
            Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
        }
        catch(UnauthorizedAccessException  e)
        {
            Console.WriteLine("A file access error occurred: {0}", e.Message);
        }

    }

    public static string DecryptTextFromFile(String FileName, byte[] Key, byte[] IV)
    {
        try
        {
            // Create or open the specified file. 
            FileStream fStream = File.Open(FileName, FileMode.OpenOrCreate);

            // Create a CryptoStream using the FileStream  
            // and the passed key and initialization vector (IV).
            CryptoStream cStream = new CryptoStream(fStream, 
                new TripleDESCryptoServiceProvider().CreateDecryptor(Key,IV), 
                CryptoStreamMode.Read); 

            // Create a StreamReader using the CryptoStream.
            StreamReader sReader = new StreamReader(cStream);

            // Read the data from the stream  
            // to decrypt it. 
            string val = sReader.ReadLine();

            // Close the streams and 
            // close the file.
            sReader.Close();
            cStream.Close();
            fStream.Close();

            // Return the string.  
            return val;
        }
        catch(CryptographicException e)
        {
            Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
            return null;
        }
        catch(UnauthorizedAccessException  e)
        {
            Console.WriteLine("A file access error occurred: {0}", e.Message);
            return null;
        }
    }
}

The following code example creates a TripleDESCryptoServiceProvider object and uses it to encrypt and decrypt data in memory.

using System;
using System.Security.Cryptography;
using System.Text;
using System.IO;

class TrippleDESCSPSample
{

    static void Main()
    {
        try
        {
            // Create a new TripleDESCryptoServiceProvider object 
            // to generate a key and initialization vector (IV).
            TripleDESCryptoServiceProvider tDESalg = new TripleDESCryptoServiceProvider();

            // Create a string to encrypt. 
            string sData = "Here is some data to encrypt.";

            // Encrypt the string to an in-memory buffer. 
            byte[] Data = EncryptTextToMemory(sData, tDESalg.Key, tDESalg.IV);

            // Decrypt the buffer back to a string. 
            string Final = DecryptTextFromMemory(Data, tDESalg.Key, tDESalg.IV);

            // Display the decrypted string to the console.
            Console.WriteLine(Final);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
        }

    }

    public static byte[] EncryptTextToMemory(string Data,  byte[] Key, byte[] IV)
    {
        try
        {
            // Create a MemoryStream.
            MemoryStream mStream = new MemoryStream();

            // Create a CryptoStream using the MemoryStream  
            // and the passed key and initialization vector (IV).
            CryptoStream cStream = new CryptoStream(mStream, 
                new TripleDESCryptoServiceProvider().CreateEncryptor(Key, IV), 
                CryptoStreamMode.Write);

            // Convert the passed string to a byte array. 
            byte[] toEncrypt = new ASCIIEncoding().GetBytes(Data);

            // Write the byte array to the crypto stream and flush it.
            cStream.Write(toEncrypt, 0, toEncrypt.Length);
            cStream.FlushFinalBlock();

            // Get an array of bytes from the  
            // MemoryStream that holds the  
            // encrypted data. 
            byte[] ret = mStream.ToArray();

            // Close the streams.
            cStream.Close();
            mStream.Close();

            // Return the encrypted buffer. 
            return ret;
        }
        catch(CryptographicException e)
        {
            Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
            return null;
        }

    }

    public static string DecryptTextFromMemory(byte[] Data,  byte[] Key, byte[] IV)
    {
        try
        {
            // Create a new MemoryStream using the passed  
            // array of encrypted data.
            MemoryStream msDecrypt = new MemoryStream(Data);

            // Create a CryptoStream using the MemoryStream  
            // and the passed key and initialization vector (IV).
            CryptoStream csDecrypt = new CryptoStream(msDecrypt, 
                new TripleDESCryptoServiceProvider().CreateDecryptor(Key, IV), 
                CryptoStreamMode.Read);

            // Create buffer to hold the decrypted data. 
            byte[] fromEncrypt = new byte[Data.Length];

            // Read the decrypted data out of the crypto stream 
            // and place it into the temporary buffer.
            csDecrypt.Read(fromEncrypt, 0, fromEncrypt.Length);

            //Convert the buffer into a string and return it. 
            return new ASCIIEncoding().GetString(fromEncrypt);
        }
        catch(CryptographicException e)
        {
            Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
            return null;
        }
    }
}

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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