Documentation for Bouncy Castle AES 256 encryption in .Net?

Question

I'm trying to implement the Bouncy Castle encryption library in a .Net project, but am not finding a lot of .Net-related documentation. The class/method structure isn't even close to the ample Java-related examples.

Does anyone have some good .Net examples for this?

Thanks.

Answer 1

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;


using System.IO;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Engines;
using Org.BouncyCastle.Crypto.Generators;
using Org.BouncyCastle.Crypto.Modes;
using Org.BouncyCastle.Crypto.Paddings;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Utilities.Encoders;

namespace BouncyCastleProject
{
    public class DesExample
    {
        // Encrypting or decrypting ?
        private bool encrypt = true;

        // To hold the initialised DESede cipher
        private PaddedBufferedBlockCipher cipher = null;

        // The input stream of bytes to be processed for encryption
        private Stream inStr = null;

        // The output stream of bytes to be procssed
        private Stream outStr = null;

        // The key
        private byte[] key = null;

        /*
        * start the application
        */
        //////public static void Main(string[] args)
        //////{
        //////    bool encrypt = true;
        //////    string infile = null;
        //////    string outfile = null;
        //////    string keyfile = null;

        //////    if (args.Length < 2)
        //////    {
        //////        //    Console.Error.WriteLine("Usage: java " + typeof(DesExample).Name + " infile outfile [keyfile]");
        //////        Console.Error.WriteLine("Usage: " + typeof(DesExample).Name + " infile outfile [keyfile]");
        //////        Environment.Exit(1);
        //////    }

        //////    keyfile = "deskey.dat";
        //////    infile = args[0];
        //////    outfile = args[1];

        //////    if (args.Length > 2)
        //////    {
        //////        encrypt = false;
        //////        keyfile = args[2];
        //////    }

        //////    DesExample de = new DesExample(infile, outfile, keyfile, encrypt);
        //////    de.process();
        //////}

        // Default constructor, used for the usage message
        public DesExample()
        {
        }

        /*
        * Constructor, that takes the arguments appropriate for
        * processing the command line directives.
        */
        public DesExample(
            string infile,
            string outfile,
            string keyfile,
            bool encrypt)
        {
            /* 
            * First, determine that infile & keyfile exist as appropriate.
            *
            * This will also create the BufferedInputStream as required
            * for reading the input file.  All input files are treated
            * as if they are binary, even if they contain text, it's the
            * bytes that are encrypted.
            */
            this.encrypt = encrypt;
            try
            {
                inStr = File.OpenRead(infile);
            }
            catch (FileNotFoundException)
            {
                //Console.Error.WriteLine("Input file not found [" + infile + "]");
                Environment.Exit(1);
            }

            try
            {
                outStr = File.Create(outfile);
            }
            catch (IOException)
            {
                //Console.Error.WriteLine("Output file not created [" + outfile + "]");
                Environment.Exit(1);
            }

            if (encrypt)
            {
                try
                {
                    /*
                    * The process of creating a new key requires a 
                    * number of steps.
                    *
                    * First, create the parameters for the key generator
                    * which are a secure random number generator, and
                    * the length of the key (in bits).
                    */
                    SecureRandom sr = new SecureRandom();

                    KeyGenerationParameters kgp = new KeyGenerationParameters(
                        sr, 
                        DesEdeParameters.DesEdeKeyLength * 8);

                    /*
                    * Second, initialise the key generator with the parameters
                    */

                    DesEdeKeyGenerator kg = new DesEdeKeyGenerator();
                    kg.Init(kgp);

                    /*
                    * Third, and finally, generate the key
                    */
                    key = kg.GenerateKey();

                    /*
                    * We can now output the key to the file, but first
                    * hex Encode the key so that we can have a look
                    * at it with a text editor if we so desire
                    */
                    Stream keystream = File.Create(keyfile);
                    byte[] keyhex = Hex.Encode(key);
                    keystream.Write(keyhex, 0, keyhex.Length);
                    keystream.Flush();
                    keystream.Close();
                }
                catch (IOException)
                {
                    //Console.Error.WriteLine("Could not decryption create key file [" + keyfile + "]");
                    Environment.Exit(1);
                }
            }
            else
            {
                try
                {
                    // TODO This block is a bit dodgy

                    // read the key, and Decode from hex encoding
                    Stream keystream = File.OpenRead(keyfile);
                    //     int len = keystream.available();
                    int len = (int)keystream.Length;
                    byte[] keyhex = new byte[len];
                    keystream.Read(keyhex, 0, len);
                    key = Hex.Decode(keyhex);
                }
                catch (IOException)
                {
                    //Console.Error.WriteLine("Decryption key file not found, or not valid [" + keyfile + "]");
                    Environment.Exit(1);
                }
            }
        }

        public void process()
        {
            /* 
            * Setup the DESede cipher engine, create a PaddedBufferedBlockCipher
            * in CBC mode.
            */
            cipher = new PaddedBufferedBlockCipher(
                new CbcBlockCipher(new DesEdeEngine()));

            /*
            * The input and output streams are currently set up
            * appropriately, and the key bytes are ready to be
            * used.
            *
            */

            if (encrypt)
            {
                performEncrypt(key);
            }
            else
            {
                performDecrypt(key);
            }

            // after processing clean up the files
            try
            {
                inStr.Close();
                outStr.Flush();
                outStr.Close();
            }
            catch (IOException)
            {
            }
        }

        /*
        * This method performs all the encryption and writes
        * the cipher text to the buffered output stream created
        * previously.
        */
        private void performEncrypt(byte[] key)
        {
            // initialise the cipher with the key bytes, for encryption
            cipher.Init(true, new KeyParameter(key));

            /*
            * Create some temporary byte arrays for use in
            * encryption, make them a reasonable size so that
            * we don't spend forever reading small chunks from
            * a file.
            *
            * There is no particular reason for using getBlockSize()
            * to determine the size of the input chunk.  It just
            * was a convenient number for the example.  
            */
            // int inBlockSize = cipher.getBlockSize() * 5;
            int inBlockSize = 47;
            int outBlockSize = cipher.GetOutputSize(inBlockSize);

            byte[] inblock = new byte[inBlockSize];
            byte[] outblock = new byte[outBlockSize];

            /* 
            * now, read the file, and output the chunks
            */
            try
            {
                int inL;
                int outL;
                byte[] rv = null;
                while ((inL = inStr.Read(inblock, 0, inBlockSize)) > 0)
                {
                    outL = cipher.ProcessBytes(inblock, 0, inL, outblock, 0);

                    /*
                    * Before we write anything out, we need to make sure
                    * that we've got something to write out. 
                    */
                    if (outL > 0)
                    {
                        rv = Hex.Encode(outblock, 0, outL);
                        outStr.Write(rv, 0, rv.Length);
                        outStr.WriteByte((byte)'\n');
                    }
                }

                try
                {
                    /*
                    * Now, process the bytes that are still buffered
                    * within the cipher.
                    */
                    outL = cipher.DoFinal(outblock, 0);
                    if (outL > 0)
                    {
                        rv = Hex.Encode(outblock, 0, outL);
                        outStr.Write(rv, 0, rv.Length);
                        outStr.WriteByte((byte)'\n');
                    }
                }
                catch (CryptoException)
                {

                }
            }
            catch (IOException ioeread)
            {
               // Console.Error.WriteLine(ioeread.StackTrace);
            }
        }

        /*
        * This method performs all the decryption and writes
        * the plain text to the buffered output stream created
        * previously.
        */
        private void performDecrypt(byte[] key)
        {
            // initialise the cipher for decryption
            cipher.Init(false, new KeyParameter(key));

            /* 
            * As the decryption is from our preformatted file,
            * and we know that it's a hex encoded format, then
            * we wrap the InputStream with a BufferedReader
            * so that we can read it easily.
            */
            //   BufferedReader br = new BufferedReader(new StreamReader(inStr));
            StreamReader br = new StreamReader(inStr); // 'inStr' already buffered

            /* 
            * now, read the file, and output the chunks
            */
            try
            {
                int outL;
                byte[] inblock = null;
                byte[] outblock = null;
                string rv = null;
                while ((rv = br.ReadLine()) != null)
                {
                    inblock = Hex.Decode(rv);
                    outblock = new byte[cipher.GetOutputSize(inblock.Length)];

                    outL = cipher.ProcessBytes(inblock, 0, inblock.Length, outblock, 0);
                    /*
                    * Before we write anything out, we need to make sure
                    * that we've got something to write out. 
                    */
                    if (outL > 0)
                    {
                        outStr.Write(outblock, 0, outL);
                    }
                }

                try
                {
                    /*
                    * Now, process the bytes that are still buffered
                    * within the cipher.
                    */
                    outL = cipher.DoFinal(outblock, 0);
                    if (outL > 0)
                    {
                        outStr.Write(outblock, 0, outL);
                    }
                }
                catch (CryptoException)
                {

                }
            }
            catch (IOException ioeread)
            {
                //Console.Error.WriteLine(ioeread.StackTrace);
            }
        }

    }
}

Answer 2

The C# classes looks almost identical to the Java classes to me. One difference is that interfaces in C# follow the .NET convention and begin with the letter 'I'. For example, IBlockCipher is the C# analog to the Java BlockCipher, and ICipherParameters corresponds to Java CipherParameters. I would expect the Java examples to translate almost perfectly into C# examples. Is there a particular java example that you are having trouble translating to C#?