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MD5 Hash - How to with .net micro framework?


#1

I have a need to compute a MD5 hash. I haven’t found any existing functions in the Microsoft or GHI libraries. Anyone know of something I can use for the .net micro framework?

Thanks, Paul


#2

You can start from this http://blogs.msdn.com/b/delay/archive/2009/01/28/thank-goodness-for-reference-implementations-low-overhead-net-md5-implementation-source-code-and-tests-works-great-on-silverlight.aspx


#3

@ Wouter Thanks for the pointer. That example class derives from the System.Security.Cryptography.HashAlgorithm abstract class. That base class isn’t in the .net micro framework, so that code probably won’t work (since I don’t know what the base class is doing).


#4

You can use this library and compile it for RLP, or convert it to C#:

http://sourceforge.net/projects/libmd5-rfc/files/

Here is another version in c++ if you prefer:

http://userpages.umbc.edu/~mabzug1/cs/md5/md5-cc-102.tar.gz


#5

MD5 will be available in .NET Micro Framework 4.2. Beta is already available bo you need to wait for GHI to release a beta sdk to use it.


#6

You only need the code starting from “MD5 implementation starts here” ignore that crypto stuff


#7

Wouter - I ran into an issue with the

System.Buffer

class missing. I guess I need to look at implementing the

Buffer.BlockCopy

method myself.

http://msdn.microsoft.com/en-us/library/system.buffer.blockcopy.aspx


#8

What about Array.Copy? Not sure what that blockcopy does, never used it.


#9

Wouter-

The difference between Buffer.BlockCopy and Array.Copy is that the buffer copies the entire block at once and then places it in the destination array. This means that the source and destination arrays can be the same, and that the bytes you are copying from in the array can overlap the bytes you are writing to (you can shift data in the array without destroying data).


#10

I have converted the code for you. Didn’t have to change a lot…


using System;

namespace FastloadMedia.NETMF.Crypto
{
    /// <summary>
    /// MD5Managed: A HashAlgorithm implementation that acts as a thin wrapper
    /// around a C# translation of the MD5 reference implementation. The C code
    /// has been translated as closely as possible so that most of the original
    /// structure remains and comparisons between the two are straightforward.
    /// </summary>
    /// <remarks>
    /// Derived from the RSA Data Security, Inc. MD5 Message-Digest Algorithm.
    /// 
    /// Specification:
    /// RFC1321 - The MD5 Message-Digest Algorithm
    /// http://www.faqs.org/rfcs/rfc1321.html
    /// 
    /// Original license:
    /// Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
    /// rights reserved.
    /// 
    /// License to copy and use this software is granted provided that it
    /// is identified as the "RSA Data Security, Inc. MD5 Message-Digest
    /// Algorithm" in all material mentioning or referencing this software
    /// or this function.
    /// 
    /// License is also granted to make and use derivative works provided
    /// that such works are identified as "derived from the RSA Data
    /// Security, Inc. MD5 Message-Digest Algorithm" in all material
    /// mentioning or referencing the derived work.
    /// 
    /// RSA Data Security, Inc. makes no representations concerning either
    /// the merchantability of this software or the suitability of this
    /// software for any particular purpose. It is provided "as is"
    /// without express or implied warranty of any kind.
    /// 
    /// These notices must be retained in any copies of any part of this
    /// documentation and/or software.
    /// </remarks>
    public class MD5Managed
    {
        // Current context
        private readonly MD5_CTX _context = new MD5_CTX();
        // Last hash result
        private readonly byte[] _digest = new byte[16];
        // True if HashCore has been called
        private bool _hashCoreCalled;
        // True if HashFinal has been called
        private bool _hashFinalCalled;

        /// <summary>
        /// Initializes a new instance.
        /// </summary>
        public MD5Managed()
        {
            InitializeVariables();
        }

        /// <summary>
        /// Initializes internal state.
        /// </summary>
        public void Initialize()
        {
            InitializeVariables();
        }

        /// <summary>
        /// Initializes variables.
        /// </summary>
        private void InitializeVariables()
        {
            MD5Init(_context);
            _hashCoreCalled = false;
            _hashFinalCalled = false;
        }

        /// <summary>
        /// Updates the hash code with the data provided.
        /// </summary>
        /// <param name="array">Data to hash.</param>
        /// <param name="ibStart">Start position.</param>
        /// <param name="cbSize">Number of bytes.</param>
        public void HashCore(byte[] array, int ibStart, int cbSize)
        {
            if (null == array)
            {
                throw new ArgumentNullException("array");
            }

            if (_hashFinalCalled)
            {
                throw new Exception("Hash not valid for use in specified state.");
            }
            _hashCoreCalled = true;

            MD5Update(_context, array, (uint)ibStart, (uint)cbSize);
        }

        /// <summary>
        /// Finalizes the hash code and returns it.
        /// </summary>
        /// <returns></returns>
        public byte[] HashFinal()
        {
            _hashFinalCalled = true;
            MD5Final(_digest, _context);
            return Hash;
        }

        /// <summary>
        /// Returns the hash as an array of bytes.
        /// </summary>
        public byte[] Hash
        {
            get
            {
                if (!_hashCoreCalled)
                {
                    throw new NullReferenceException();
                }
                if (!_hashFinalCalled)
                {
                    // Note: Not CryptographicUnexpectedOperationException because that can't be instantiated on Silverlight 4
                    throw new Exception("Hash must be finalized before the hash value is retrieved.");
                }

                return _digest;
            }
        }

        /// <summary>
        /// Gets the size of hash in bits.
        /// </summary>
        public int HashSize
        {
            get
            {
                return _digest.Length * 8;
            }
        }

        ///////////////////////////////////////////////
        // MD5 reference implementation begins here. //
        ///////////////////////////////////////////////

        /* MD5 context. */
        private class MD5_CTX
        {
            public readonly uint[] state;   /* state (ABCD) */
            public readonly uint[] count;   /* number of bits, modulo 2^64 (lsb first) */
            public readonly byte[] buffer;  /* input buffer */

            public MD5_CTX()
            {
                state = new uint[4];
                count = new uint[2];
                buffer = new byte[64];
            }

            public void Clear()
            {
                Array.Clear(state, 0, state.Length);
                Array.Clear(count, 0, count.Length);
                Array.Clear(buffer, 0, buffer.Length);
            }
        }

        /* Constants for MD5Transform routine. */
        private const int S11 = 7;
        private const int S12 = 12;
        private const int S13 = 17;
        private const int S14 = 22;
        private const int S21 = 5;
        private const int S22 = 9;
        private const int S23 = 14;
        private const int S24 = 20;
        private const int S31 = 4;
        private const int S32 = 11;
        private const int S33 = 16;
        private const int S34 = 23;
        private const int S41 = 6;
        private const int S42 = 10;
        private const int S43 = 15;
        private const int S44 = 21;

        private static byte[] PADDING;

        static MD5Managed()
        {
            PADDING = new byte[64];
            PADDING[0] = 0x80;
        }

        /* F, G, H and I are basic MD5 functions. */
        private static uint F(uint x, uint y, uint z) { return (((x) & (y)) | ((~x) & (z))); }
        private static uint G(uint x, uint y, uint z) { return (((x) & (z)) | ((y) & (~z))); }
        private static uint H(uint x, uint y, uint z) { return ((x) ^ (y) ^ (z)); }
        private static uint I(uint x, uint y, uint z) { return ((y) ^ ((x) | (~z))); }

        /* ROTATE_LEFT rotates x left n bits. */
        private static uint ROTATE_LEFT(uint x, int n) { return (((x) << (n)) | ((x) >> (32 - (n)))); }

        /* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
           Rotation is separate from addition to prevent recomputation. */
        private static void FF(ref uint a, uint b, uint c, uint d, uint x, int s, uint ac)
        {
            (a) += F((b), (c), (d)) + (x) + (uint)(ac);
            (a) = ROTATE_LEFT((a), (s));
            (a) += (b);
        }
        private static void GG(ref uint a, uint b, uint c, uint d, uint x, int s, uint ac)
        {
            (a) += G((b), (c), (d)) + (x) + (uint)(ac);
            (a) = ROTATE_LEFT((a), (s));
            (a) += (b);
        }
        private static void HH(ref uint a, uint b, uint c, uint d, uint x, int s, uint ac)
        {
            (a) += H((b), (c), (d)) + (x) + (uint)(ac);
            (a) = ROTATE_LEFT((a), (s));
            (a) += (b);
        }
        private static void II(ref uint a, uint b, uint c, uint d, uint x, int s, uint ac)
        {
            (a) += I((b), (c), (d)) + (x) + (uint)(ac);
            (a) = ROTATE_LEFT((a), (s));
            (a) += (b);
        }

        /* MD5 initialization. Begins an MD5 operation, writing a new context. */
        private static void MD5Init(MD5_CTX context)  /* context */
        {
            context.count[0] = context.count[1] = 0;

            /* Load magic initialization constants. */
            context.state[0] = 0x67452301;
            context.state[1] = 0xefcdab89;
            context.state[2] = 0x98badcfe;
            context.state[3] = 0x10325476;
        }

        /* MD5 block update operation. Continues an MD5 message-digest
           operation, processing another message block, and updating the
           context. */
        private static void MD5Update(MD5_CTX context,  /* context */
                                      byte[] input,     /* input block */
                                      uint inputIndex,  // Starting index for input block
                                      uint inputLen)    /* length of input block */
        {
            /* Compute number of bytes mod 64 */
            uint index = (uint)((context.count[0] >> 3) & 0x3F);

            /* Update number of bits */
            if ((context.count[0] += ((uint)inputLen << 3)) < ((uint)inputLen << 3))
            {
                context.count[1]++;
            }
            context.count[1] += ((uint)inputLen >> 29);

            uint partLen = 64 - index;

            /* Transform as many times as possible. */
            uint i = 0;
            if (inputLen >= partLen)
            {
                Array.Copy(input, (int)inputIndex, context.buffer, (int)index, (int)partLen);

                MD5Transform(context.state, context.buffer, 0);

                for (i = partLen; i + 63 < inputLen; i += 64)
                {
                    MD5Transform(context.state, input, inputIndex + i);
                }

                index = 0;
            }

            /* Buffer remaining input */
            Array.Copy(input, (int)(inputIndex + i), context.buffer, (int)index, (int)(inputLen - i));
        }

        /* MD5 finalization. Ends an MD5 message-digest operation, writing the
           the message digest and zeroizing the context. */
        private static void MD5Final(byte[] digest,    /* message digest */
                                     MD5_CTX context)  /* context */
        {
            byte[] bits = new byte[8];

            /* Save number of bits */
            Encode(bits, context.count, 8);

            /* Pad out to 56 mod 64. */
            uint index = (uint)((context.count[0] >> 3) & 0x3f);
            uint padLen = (index < 56) ? (56 - index) : (120 - index);
            MD5Update(context, PADDING, 0, padLen);

            /* Append length (before padding) */
            MD5Update(context, bits, 0, 8);

            /* Store state in digest */
            Encode(digest, context.state, 16);

            /* Zeroize sensitive information. */
            context.Clear();
        }

        /* MD5 basic transformation. Transforms state based on block. */
        private static void MD5Transform(uint[] state,
                                         byte[] block,
                                         uint blockIndex)
        {
            uint a = state[0], b = state[1], c = state[2], d = state[3];
            uint[] x = new uint[16];

            Decode(x, block, blockIndex, 64);

            /* Round 1 */
            FF(ref a, b, c, d, x[0], S11, 0xd76aa478); /* 1 */
            FF(ref d, a, b, c, x[1], S12, 0xe8c7b756); /* 2 */
            FF(ref c, d, a, b, x[2], S13, 0x242070db); /* 3 */
            FF(ref b, c, d, a, x[3], S14, 0xc1bdceee); /* 4 */
            FF(ref a, b, c, d, x[4], S11, 0xf57c0faf); /* 5 */
            FF(ref d, a, b, c, x[5], S12, 0x4787c62a); /* 6 */
            FF(ref c, d, a, b, x[6], S13, 0xa8304613); /* 7 */
            FF(ref b, c, d, a, x[7], S14, 0xfd469501); /* 8 */
            FF(ref a, b, c, d, x[8], S11, 0x698098d8); /* 9 */
            FF(ref d, a, b, c, x[9], S12, 0x8b44f7af); /* 10 */
            FF(ref c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
            FF(ref b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
            FF(ref a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
            FF(ref d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
            FF(ref c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
            FF(ref b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

            /* Round 2 */
            GG(ref a, b, c, d, x[1], S21, 0xf61e2562); /* 17 */
            GG(ref d, a, b, c, x[6], S22, 0xc040b340); /* 18 */
            GG(ref c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
            GG(ref b, c, d, a, x[0], S24, 0xe9b6c7aa); /* 20 */
            GG(ref a, b, c, d, x[5], S21, 0xd62f105d); /* 21 */
            GG(ref d, a, b, c, x[10], S22, 0x02441453); /* 22 */
            GG(ref c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
            GG(ref b, c, d, a, x[4], S24, 0xe7d3fbc8); /* 24 */
            GG(ref a, b, c, d, x[9], S21, 0x21e1cde6); /* 25 */
            GG(ref d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
            GG(ref c, d, a, b, x[3], S23, 0xf4d50d87); /* 27 */
            GG(ref b, c, d, a, x[8], S24, 0x455a14ed); /* 28 */
            GG(ref a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
            GG(ref d, a, b, c, x[2], S22, 0xfcefa3f8); /* 30 */
            GG(ref c, d, a, b, x[7], S23, 0x676f02d9); /* 31 */
            GG(ref b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

            /* Round 3 */
            HH(ref a, b, c, d, x[5], S31, 0xfffa3942); /* 33 */
            HH(ref d, a, b, c, x[8], S32, 0x8771f681); /* 34 */
            HH(ref c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
            HH(ref b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
            HH(ref a, b, c, d, x[1], S31, 0xa4beea44); /* 37 */
            HH(ref d, a, b, c, x[4], S32, 0x4bdecfa9); /* 38 */
            HH(ref c, d, a, b, x[7], S33, 0xf6bb4b60); /* 39 */
            HH(ref b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
            HH(ref a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
            HH(ref d, a, b, c, x[0], S32, 0xeaa127fa); /* 42 */
            HH(ref c, d, a, b, x[3], S33, 0xd4ef3085); /* 43 */
            HH(ref b, c, d, a, x[6], S34, 0x04881d05); /* 44 */
            HH(ref a, b, c, d, x[9], S31, 0xd9d4d039); /* 45 */
            HH(ref d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
            HH(ref c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
            HH(ref b, c, d, a, x[2], S34, 0xc4ac5665); /* 48 */

            /* Round 4 */
            II(ref a, b, c, d, x[0], S41, 0xf4292244); /* 49 */
            II(ref d, a, b, c, x[7], S42, 0x432aff97); /* 50 */
            II(ref c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
            II(ref b, c, d, a, x[5], S44, 0xfc93a039); /* 52 */
            II(ref a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
            II(ref d, a, b, c, x[3], S42, 0x8f0ccc92); /* 54 */
            II(ref c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
            II(ref b, c, d, a, x[1], S44, 0x85845dd1); /* 56 */
            II(ref a, b, c, d, x[8], S41, 0x6fa87e4f); /* 57 */
            II(ref d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
            II(ref c, d, a, b, x[6], S43, 0xa3014314); /* 59 */
            II(ref b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
            II(ref a, b, c, d, x[4], S41, 0xf7537e82); /* 61 */
            II(ref d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
            II(ref c, d, a, b, x[2], S43, 0x2ad7d2bb); /* 63 */
            II(ref b, c, d, a, x[9], S44, 0xeb86d391); /* 64 */

            state[0] += a;
            state[1] += b;
            state[2] += c;
            state[3] += d;

            /* Zeroize sensitive information. */
            Array.Clear(x, 0, x.Length);
        }

        /* Encodes input (UINT4) into output (unsigned char). Assumes len is
           a multiple of 4. */
        private static void Encode(byte[] output,
                                   uint[] input,
                                   uint len)
        {
            for (uint i = 0, j = 0; j < len; i++, j += 4)
            {
                output[j] = (byte)(input[i] & 0xff);
                output[j + 1] = (byte)((input[i] >> 8) & 0xff);
                output[j + 2] = (byte)((input[i] >> 16) & 0xff);
                output[j + 3] = (byte)((input[i] >> 24) & 0xff);
            }
        }

        /* Decodes input (unsigned char) into output (UINT4). Assumes len is
           a multiple of 4. */
        private static void Decode(uint[] output,
                                   byte[] input,
                                   uint inputIndex,
                                   uint len)
        {
            for (uint i = 0, j = 0; j < len; i++, j += 4)
            {
                output[i] = ((uint)input[inputIndex + j]) |
                    (((uint)input[inputIndex + j + 1]) << 8) |
                    (((uint)input[inputIndex + j + 2]) << 16) |
                    (((uint)input[inputIndex + j + 3]) << 24);
            }
        }
    }
}

Usage:


MD5Managed test = new MD5Managed();

string text = "TEST";

test.HashCore(Encoding.UTF8.GetBytes(text), 0, text.Length);
byte[] hash = test.HashFinal();

Tested it, and it works.


#11

Wouter - Wow, thanks for converting this! I’ll give it a try as soon as I can. I have copied it into my project, it compiles no problem. It’ll probably be a few days before I can actually test it, but it looks like you already proved it works. Thanks again.

Paul


#12

Hello,

I try to use the MD5Managed code but I only get something with strings smaller than 16 chars. If I try bigger string I get nothing.

Did you encountered this problem ?

Lionel


            MD5Managed md5 = new MD5Managed();
            string text = "The quick brown fox jumps over the lazy dog";
            md5.HashCore(Encoding.UTF8.GetBytes(text), 0, text.Length);
            
            var buffer = md5.HashFinal();

            Debug.Print(new StreamReader(new MemoryStream(buffer)).ReadToEnd());
            Debug.Print("Length : " + buffer.Length);

Result :
The thread ‘’ (0x2) has exited with code 0 (0x0).
Done.

Length : 16
The thread ‘’ (0x1) has exited with code 0 (0x0).
The program ‘[1020] Micro Framework application: Managed’ has exited with code 0 (0x0).


#13

I tried your code but modified the output method and I see no problems. The hash in output window is correct.


MD5Managed md5 = new MD5Managed();
string text = "The quick brown fox jumps over the lazy dog";
md5.HashCore(Encoding.UTF8.GetBytes(text), 0, text.Length);

byte[] buffer = md5.HashFinal();

char[] output = new char[buffer.Length * 2];
for (int i = 0; i < buffer.Length; i++)
{
    output[(i << 1) + 0] = (buffer[i] >> 4) <= 9 ? (char)((buffer[i] >> 4) + '0') : (char)((buffer[i] >> 4) - 10 + 'A');
    output[(i << 1) + 1] = (buffer[i] & 15) <= 9 ? (char)((buffer[i] & 15) + '0') : (char)((buffer[i] & 15) - 10 + 'A');
}

Debug.Print(new string(output));


#14

Hello Wouter,

Thanks for your help. I used a wrong displaying method.

Lionel