MD5CryptoServiceProvider Class
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MD5CryptoServiceProvider Class

 

Computes the MD5 hash value for the input data using the implementation provided by the cryptographic service provider (CSP). This class cannot be inherited.

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

System.Object
  System.Security.Cryptography.HashAlgorithm
    System.Security.Cryptography.MD5
      System.Security.Cryptography.MD5CryptoServiceProvider

[ComVisibleAttribute(true)]
public sealed class MD5CryptoServiceProvider : MD5

NameDescription
System_CAPS_pubmethodMD5CryptoServiceProvider()

Initializes a new instance of the MD5CryptoServiceProvider class.

NameDescription
System_CAPS_pubpropertyCanReuseTransform

Gets a value indicating whether the current transform can be reused.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyCanTransformMultipleBlocks

When overridden in a derived class, gets a value indicating whether multiple blocks can be transformed.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyHash

Gets the value of the computed hash code.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyHashSize

Gets the size, in bits, of the computed hash code.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyInputBlockSize

When overridden in a derived class, gets the input block size.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyOutputBlockSize

When overridden in a derived class, gets the output block size.(Inherited from HashAlgorithm.)

NameDescription
System_CAPS_pubmethodClear()

Releases all resources used by the HashAlgorithm class.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodComputeHash(Byte[])

Computes the hash value for the specified byte array.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodComputeHash(Byte[], Int32, Int32)

Computes the hash value for the specified region of the specified byte array.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodComputeHash(Stream)

Computes the hash value for the specified Stream object.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodDispose()

Releases all resources used by the current instance of the HashAlgorithm class.(Inherited from HashAlgorithm.)

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_pubmethodInitialize()

Initializes an instance of MD5CryptoServiceProvider.(Overrides HashAlgorithm.Initialize().)

System_CAPS_pubmethodToString()

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

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

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.)

System_CAPS_pubmethodTransformFinalBlock(Byte[], Int32, Int32)

Computes the hash value for the specified region of the specified byte array.(Inherited from HashAlgorithm.)

NameDescription
System_CAPS_protfieldHashValue

Represents the value of the computed hash code.(Inherited from HashAlgorithm.)

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.

System_CAPS_noteNote

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 MD5CryptoServiceProvider class. Use MD5CryptoServiceProvider only for compatibility with legacy applications and data.

The hash size for the MD5CryptoServiceProvider class is 128 bits.

The ComputeHash methods of the MD5CryptoServiceProvider 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.

The following code example computes the MD5 hash value for data and returns it.

byte[] MD5hash (byte[] data)
 {
    // This is one implementation of the abstract class MD5.
    MD5 md5 = new MD5CryptoServiceProvider();

    byte[] result = md5.ComputeHash(data);

    return result;
 }

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;

class Example
{
    // Hash an input string and return the hash as
    // a 32 character hexadecimal string.
    static string getMd5Hash(string input)
    {
        // Create a new instance of the MD5CryptoServiceProvider object.
        MD5CryptoServiceProvider md5Hasher = new MD5CryptoServiceProvider();

        // Convert the input string to a byte array and compute the hash.
        byte[] data = md5Hasher.ComputeHash(Encoding.Default.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(string input, string hash)
    {
        // Hash the input.
        string hashOfInput = getMd5Hash(input);

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

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


    static void Main()
    {
        string source = "Hello World!";

        string hash = getMd5Hash(source);

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

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

        if (verifyMd5Hash(source, hash))
        {
            Console.WriteLine("The hashes are the same.");
        }
        else
        {
            Console.WriteLine("The hashes are not same.");
        }

    }
}
// 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
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.

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