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MD5 Class

Updated: June 2011

Represents the abstract class from which all implementations of the MD5 hash algorithm inherit.

Namespace:  System.Security.Cryptography
Assembly:  mscorlib (in mscorlib.dll)
[ComVisibleAttribute(true)]
public abstract class MD5 : HashAlgorithm

The MD5 type exposes the following members.

  Name Description
Protected method MD5 Initializes a new instance of MD5.
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  Name Description
Public property CanReuseTransform Gets a value indicating whether the current transform can be reused. (Inherited from HashAlgorithm.)
Public property CanTransformMultipleBlocks When overridden in a derived class, gets a value indicating whether multiple blocks can be transformed. (Inherited from HashAlgorithm.)
Public property Hash Gets the value of the computed hash code. (Inherited from HashAlgorithm.)
Public property HashSize Gets the size, in bits, of the computed hash code. (Inherited from HashAlgorithm.)
Public property InputBlockSize When overridden in a derived class, gets the input block size. (Inherited from HashAlgorithm.)
Public property OutputBlockSize When overridden in a derived class, gets the output block size. (Inherited from HashAlgorithm.)
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  Name Description
Public method Clear Releases all resources used by the HashAlgorithm class. (Inherited from HashAlgorithm.)
Public method ComputeHash(Byte()) Computes the hash value for the specified byte array. (Inherited from HashAlgorithm.)
Public method ComputeHash(Stream) Computes the hash value for the specified Stream object. (Inherited from HashAlgorithm.)
Public method ComputeHash(Byte(), Int32, Int32) Computes the hash value for the specified region of the specified byte array. (Inherited from HashAlgorithm.)
Public method Static member Create Creates an instance of the default implementation of the MD5 hash algorithm.
Public method Static member Create(String) Creates an instance of the specified implementation of the MD5 hash algorithm.
Public method Dispose Releases all resources used by the current instance of the HashAlgorithm class. (Inherited from HashAlgorithm.)
Protected method Dispose(Boolean) Releases the unmanaged resources used by the HashAlgorithm and optionally releases the managed resources. (Inherited from HashAlgorithm.)
Public method Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected method Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public method GetType Gets the Type of the current instance. (Inherited from Object.)
Protected method HashCore When overridden in a derived class, routes data written to the object into the hash algorithm for computing the hash. (Inherited from HashAlgorithm.)
Protected method HashFinal When overridden in a derived class, finalizes the hash computation after the last data is processed by the cryptographic stream object. (Inherited from HashAlgorithm.)
Public method Initialize Initializes an implementation of the HashAlgorithm class. (Inherited from HashAlgorithm.)
Protected method MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method ToString Returns a string that represents the current object. (Inherited from Object.)
Public method TransformBlock Computes the hash value for the specified region of the input byte array and copies the specified region of the input byte array to the specified region of the output byte array. (Inherited from HashAlgorithm.)
Public method TransformFinalBlock Computes the hash value for the specified region of the specified byte array. (Inherited from HashAlgorithm.)
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  Name Description
Protected field HashSizeValue Represents the size, in bits, of the computed hash code. (Inherited from HashAlgorithm.)
Protected field HashValue Represents the value of the computed hash code. (Inherited from HashAlgorithm.)
Protected field State Represents the state of the hash computation. (Inherited from HashAlgorithm.)
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Hash functions map binary strings of an arbitrary length to small binary strings of a fixed length. A cryptographic hash function has the property that it is computationally infeasible to find two distinct inputs that hash to the same value; that is, hashes of two sets of data should match if the corresponding data also matches. Small changes to the data result in large, unpredictable changes in the hash.

The hash size for the MD5 algorithm is 128 bits.

The ComputeHash methods of the MD5 class return the hash as an array of 16 bytes. Note that some MD5 implementations produce a 32-character, hexadecimal-formatted hash. To interoperate with such implementations, format the return value of the ComputeHash methods as a hexadecimal value.

Note Note

Newer hash functions, such as the Secure Hash Algorithms SHA-256 and SHA-512, are available. Consider using the SHA256 class or the SHA512 class instead of the MD5 class.

The following code example computes the MD5 hash value of a string and returns the hash as a 32-character, hexadecimal-formatted string. The hash string created by this code example is compatible with any MD5 hash function (on any platform) that creates a 32-character, hexadecimal-formatted hash string.


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

namespace MD5Sample
{
    class Program
    {
        static void Main(string[] args)
        {
            string source = "Hello World!";
            using (MD5 md5Hash = MD5.Create())
            {
                string hash = GetMd5Hash(md5Hash, source);

                Console.WriteLine("The MD5 hash of " + source + " is: " + hash + ".");

                Console.WriteLine("Verifying the hash...");

                if (VerifyMd5Hash(md5Hash, source, hash))
                {
                    Console.WriteLine("The hashes are the same.");
                }
                else
                {
                    Console.WriteLine("The hashes are not same.");
                }
            }



        }
        static string GetMd5Hash(MD5 md5Hash, string input)
        {

            // Convert the input string to a byte array and compute the hash.
            byte[] data = md5Hash.ComputeHash(Encoding.UTF8.GetBytes(input));

            // Create a new Stringbuilder to collect the bytes
            // and create a string.
            StringBuilder sBuilder = new StringBuilder();

            // Loop through each byte of the hashed data 
            // and format each one as a hexadecimal string.
            for (int i = 0; i < data.Length; i++)
            {
                sBuilder.Append(data[i].ToString("x2"));
            }

            // Return the hexadecimal string.
            return sBuilder.ToString();
        }

        // Verify a hash against a string.
        static bool VerifyMd5Hash(MD5 md5Hash, string input, string hash)
        {
            // Hash the input.
            string hashOfInput = GetMd5Hash(md5Hash, input);

            // Create a StringComparer an compare the hashes.
            StringComparer comparer = StringComparer.OrdinalIgnoreCase;

            if (0 == comparer.Compare(hashOfInput, hash))
            {
                return true;
            }
            else
            {
                return false;
            }
        }

    }
}

// This code example produces the following output:
//
// The MD5 hash of Hello World! is: ed076287532e86365e841e92bfc50d8c.
// Verifying the hash...
// The hashes are the same.


.NET Framework

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

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Date

History

Reason

June 2011

Added note about newer hash functions SHA-256 and SHA-512.

Information enhancement.

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One Liner
string Hash = BitConverter.ToString(md5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(StringValueToHash))).Replace("-",string.Empty);
Do not forget go clear (dispose)
The md5 hash algorithm use unmanaged ressources. NEVER forget to call clear (some sort of dispose) or else your will get memory leaks after some days of running your application that calls this method. So, 2 things to change. First, add a "clear" after using the md5hasher. Second, if you want to correctly get md5 of chinese characters, replace "encoding.default.getbytes" by "encoding.utf8.getbytes"
Generate MD5 hash of a string in C#
I have written a simple method to generate MD5 or SHA1 hash value for string. Check it out "Generate MD5 hash of a string in C#" [http://www.mujahiddev.com/2010/09/simple-hashing.html]
A one-liner
Ok, maybe not quite ONE line.  This will do the trick: $0$0 $0 $0(requires LINQ)$0 $0$0 $0 $0System.Security.Cryptography.MD5.Create()$0 $0.ComputeHash(Encoding.Default.GetBytes(tohash))$0 $0.Select(x => x.ToString("x2"))$0 $0.Aggregate(new System.Text.StringBuilder(), (acc, x) => acc.Append(x))$0 $0.ToString();$0 $0 $0