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Implementation of the MD5 Algorithm in C# for the Compact Framework on PocketPC

The cryptography classes are not available on the Compact Framework 1.0, so we ported the "MD5 Message-Digest Algorithm" from RSA Data Security, Inc. in C#.

These classes are supported by the Compact Framework 2.0

Using the MD5 and MD5CryptoServiceProvider classes

With the .Net Framework, the MD5 hash of the buffer can be computed this way:

using System;
using System.Text;
using System.Security.Cryptography;
...
        byte[] ComputeMD5(byte[] buffer)
        {
            //Create the md5 hash provider.
            MD5 md = new MD5CryptoServiceProvider();

            //Compute the hash value from the array of bytes.
            return md.ComputeHash(buffer);
        }
...

We implemented both classes, trying to keep the same signatures for their methods. So we switch to our implementation simply by changing the using.

using System;
using System.Text;
//using System.Security.Cryptography;
using FlowGroup.Crypto;
...
        byte[] ComputeMD5(byte[] buffer)
        {
            //Create the md5 hash provider.
            MD5 md = new MD5CryptoServiceProvider();

            //Compute the hash value from the array of bytes.
            return md.ComputeHash(buffer);
        }
...

We could have used the following methods to get the hash algoritm:

MD5 md = MD5.Create();
MD5 md = MD5.Create("MD5");

But, HashAlgorithm doest not exist on the Compact Framework and we did not defined it, so the following code does not work:

HashAlgorithm md = HashAlgorithm.Create("MD5");

Test Suite

The code can be downloaded here. As a sample demonstrating how to use it, let's implement the test suite from the RFC 1321.

using System;
using System.Text;
using FlowGroup.Crypto;

namespace DemoMD5
{
    /// <summary>
    /// Summary description for Application.
    /// </summary>
    class Application
    {
        static private void MDString(string s)
        {
            MD5 md = MD5CryptoServiceProvider.Create();
            byte[] hash;

            //Create a new instance of ASCIIEncoding to 
            //convert the string into an array of Unicode bytes.
            ASCIIEncoding enc = new ASCIIEncoding();

            //Convert the string into an array of bytes.
            byte[] buffer = enc.GetBytes(s);

            //Create the hash value from the array of bytes.
            hash = md.ComputeHash(buffer);

            //Display the hash value to the console. 
            Console.Write("MD5 (\"{0}\") = ", s);
            foreach(byte b in hash)
            {
                Console.Write(b.ToString("x2"));
            }
            Console.WriteLine("");
        }

        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            Console.WriteLine("MD5 test suite:");
            MDString("");
            MDString("a");
            MDString("abc");
            MDString("message digest");
            MDString("abcdefghijklmnopqrstuvwxyz");
            MDString("ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                     + "abcdefghijklmnopqrstuvwxyz"
                     + "0123456789");
            MDString("123456789012345678901234567890"
                     + "123456789012345678901234567890"
                     + "12345678901234567890"); 
        }
    }
}

Output

The output is the following, as excepted from RFC 1321 :

MD5 test suite:¶
MD5 ("") = d41d8cd98f00b204e9800998ecf8427e¶
MD5 ("a") = 0cc175b9c0f1b6a831c399e269772661¶
MD5 ("abc") = 900150983cd24fb0d6963f7d28e17f72¶
MD5 ("message digest") = f96b697d7cb7938d525a2f31aaf161d0¶
MD5 ("abcdefghijklmnopqrstuvwxyz") = c3fcd3d76192e4007dfb496cca67e13b¶
MD5 ("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789") = 
d174ab98d277d9f5a5611c2c9f419d9f¶
MD5 ("123456789012345678901234567890123456789012345678901234567890123456
78901234567890") = 57edf4a22be3c955ac49da2e2107b67a¶

Some useful links...

	RFC 1321 RFC describing the MD5 algorithm
	Download the source code size 4 Kb, last modification date 06/08/2013
	Download the Visual Studio 2003 solution size 8 Kb, last modification date 06/08/2013
	Contacts us Any comments, questions? Just contact us.

Revision history...

date	révision
29/12/2005 00:00	Add the implementation of: `public byte[] ComputeHash(Stream inputStream)` `public int TransformBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)` `public byte[] TransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)` Modify HashCore to allow it to be called several times.

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