CryptoAPITransform Class
TOC
Collapse the table of content
Expand the table of content

CryptoAPITransform Class

 

Performs a cryptographic transformation of data. This class cannot be inherited.

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

System.Object
  System.Security.Cryptography.CryptoAPITransform

[ComVisibleAttribute(true)]
public sealed class CryptoAPITransform : ICryptoTransform, IDisposable

NameDescription
System_CAPS_pubpropertyCanReuseTransform

Gets a value indicating whether the current transform can be reused.

System_CAPS_pubpropertyCanTransformMultipleBlocks

Gets a value indicating whether multiple blocks can be transformed.

System_CAPS_pubpropertyInputBlockSize

Gets the input block size.

System_CAPS_pubpropertyKeyHandle

Gets the key handle.

System_CAPS_pubpropertyOutputBlockSize

Gets the output block size.

NameDescription
System_CAPS_pubmethodClear()

Releases all resources used by the CryptoAPITransform method.

System_CAPS_pubmethodDispose()

Releases all resources used by the current instance of the CryptoAPITransform class.

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethodReset()

Resets the internal state of CryptoAPITransform so that it can be used again to do a different encryption or decryption.

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

System_CAPS_pubmethodTransformBlock(Byte[], Int32, Int32, Byte[], Int32)

Computes the transformation for the specified region of the input byte array and copies the resulting transformation to the specified region of the output byte array.

System_CAPS_pubmethodTransformFinalBlock(Byte[], Int32, Int32)

Computes the transformation for the specified region of the specified byte array.

The following code example demonstrates how to use members of the CryptoAPITransform class.

using System;
using System.Security.Cryptography;
using System.Collections;
using System.Text;

class Members
{
    // Use a public service provider for encryption and decryption.
    static DESCryptoServiceProvider des = new DESCryptoServiceProvider();

    [STAThread]
    static void Main(string[] args)
    {
        string message = "012345678901234567890";
        byte[] sourceBytes = Encoding.ASCII.GetBytes(message);
        Console.WriteLine("** Phrase to be encoded: " + message);

        byte[] encodedBytes = EncodeBytes(sourceBytes);
        Console.WriteLine("** Phrase after encoding: " +
            Encoding.ASCII.GetString(encodedBytes));

        byte[] decodedBytes = DecodeBytes(encodedBytes);
        Console.WriteLine("** Phrase after decoding: " +
            Encoding.ASCII.GetString(decodedBytes));

        Console.WriteLine("Sample ended successfully; " +
            "press Enter to continue.");
        Console.ReadLine();
    }

    // Encode the specified byte array by using CryptoAPITranform.
    private static byte[] EncodeBytes(byte[] sourceBytes)
    {
        int currentPosition = 0;
        byte[] targetBytes = new byte[1024];
        int sourceByteLength = sourceBytes.Length;

        // Create a DES encryptor from this instance to perform encryption.
        CryptoAPITransform cryptoTransform =
            (CryptoAPITransform)des.CreateEncryptor();

        // Retrieve the block size to read the bytes.
        int inputBlockSize = cryptoTransform.InputBlockSize;

        // Retrieve the key handle.
        IntPtr keyHandle = cryptoTransform.KeyHandle;

        // Retrieve the block size to write the bytes.
        int outputBlockSize = cryptoTransform.OutputBlockSize;

        try
        {
            // Determine if multiple blocks can be transformed.
            if (cryptoTransform.CanTransformMultipleBlocks)
            {
                int numBytesRead = 0;
                while (sourceByteLength - currentPosition >= inputBlockSize)
                {
                    // Transform the bytes from currentPosition in the
                    // sourceBytes array, writing the bytes to the targetBytes
                    // array.
                    numBytesRead = cryptoTransform.TransformBlock(
                        sourceBytes,
                        currentPosition,
                        inputBlockSize,
                        targetBytes,
                        currentPosition);

                    // Advance the current position in the sourceBytes array.
                    currentPosition += numBytesRead;
                }

                // Transform the final block of bytes.
                byte[] finalBytes = cryptoTransform.TransformFinalBlock(
                    sourceBytes,
                    currentPosition,
                    sourceByteLength - currentPosition);

                // Copy the contents of the finalBytes array to the
                // targetBytes array.
                finalBytes.CopyTo(targetBytes, currentPosition);
            }

        }
        catch (Exception ex)
        {
            Console.WriteLine("Caught unexpected exception:" + ex.ToString());
        }

        // Determine if the current transform can be reused.
        if (!cryptoTransform.CanReuseTransform)
        {
            // Free up any used resources.
            cryptoTransform.Clear();
        }

        // Trim the extra bytes in the array that were not used.
        return TrimArray(targetBytes);
    }

    // Decode the specified byte array using CryptoAPITranform.
    private static byte[] DecodeBytes(byte[] sourceBytes)
    {
        byte[] targetBytes = new byte[1024];
        int currentPosition = 0;

        // Create a DES decryptor from this instance to perform decryption.
        CryptoAPITransform cryptoTransform =
            (CryptoAPITransform)des.CreateDecryptor();

        int inputBlockSize = cryptoTransform.InputBlockSize;
        int sourceByteLength = sourceBytes.Length;

        try
        {
            int numBytesRead = 0;
            while (sourceByteLength - currentPosition >= inputBlockSize)
            {
                // Transform the bytes from current position in the 
                // sourceBytes array, writing the bytes to the targetBytes
                // array.
                numBytesRead = cryptoTransform.TransformBlock(
                    sourceBytes,
                    currentPosition,
                    inputBlockSize,
                    targetBytes,
                    currentPosition);

                // Advance the current position in the source array.
                currentPosition += numBytesRead;
            }

            // Transform the final block of bytes.
            byte[] finalBytes = cryptoTransform.TransformFinalBlock(
                sourceBytes,
                currentPosition,
                sourceByteLength - currentPosition);

            // Copy the contents of the finalBytes array to the targetBytes
            // array.
            finalBytes.CopyTo(targetBytes, currentPosition);
        }
        catch (Exception ex)
        {
            Console.WriteLine("Caught unexpected exception:" + ex.ToString());
        }

        // Strip out the second block of bytes.
        Array.Copy(targetBytes, (inputBlockSize * 2), targetBytes, inputBlockSize, targetBytes.Length - (inputBlockSize * 2));

        // Trim the extra bytes in the array that were not used.
        return TrimArray(targetBytes);
    }

    // Resize the dimensions of the array to a size that contains only valid
    // bytes.
    private static byte[] TrimArray(byte[] targetArray)
    {
        IEnumerator enum1 = targetArray.GetEnumerator();
        int i = 0;

        while (enum1.MoveNext())
        {
            if (enum1.Current.ToString().Equals("0"))
            {
                break;
            }
            i++;
        }

        // Create a new array with the number of valid bytes.
        byte[] returnedArray = new byte[i];
        for (int j = 0; j < i; j++)
        {
            returnedArray[j] = targetArray[j];
        }

        return returnedArray;
    }
}
//
// This sample produces the following output:
//
// ** Phrase to be encoded: 012345678901234567890
// ** Phrase after encoding: AIGC(+b7X?^djAU?15ve?o
// ** Phrase after decoding: 012345678901234567890
// Sample ended successfully; press Enter to continue.

.NET Framework
Available since 1.1

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

Return to top
Show:
© 2016 Microsoft