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)

<ComVisibleAttribute(True)> _
Public NotInheritable Class MD5CryptoServiceProvider
	Inherits MD5
Dim instance As MD5CryptoServiceProvider

/** @attribute ComVisibleAttribute(true) */ 
public final class MD5CryptoServiceProvider extends MD5
public final class MD5CryptoServiceProvider extends MD5

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 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.

Function MD5hash(data() As Byte) As Byte()
    ' This is one implementation of the abstract class MD5.
    Dim md5 As New MD5CryptoServiceProvider()
    Dim result As Byte() = md5.ComputeHash(data)
    Return result
End Function

ubyte[] MD5hash(ubyte data[])
    // This is one implementation of the abstract class MD5.
    MD5 md5 = new MD5CryptoServiceProvider();
    ubyte result[] = md5.ComputeHash(data);
    return result;
} //MD5hash

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.

Imports System
Imports System.Security.Cryptography
Imports System.Text

Module Example

    ' Hash an input string and return the hash as
    ' a 32 character hexadecimal string.
    Function getMd5Hash(ByVal input As String) As String
        ' Create a new instance of the MD5CryptoServiceProvider object.
        Dim md5Hasher As New MD5CryptoServiceProvider()

        ' Convert the input string to a byte array and compute the hash.
        Dim data As Byte() = md5Hasher.ComputeHash(Encoding.Default.GetBytes(input))

        ' Create a new Stringbuilder to collect the bytes
        ' and create a string.
        Dim sBuilder As New StringBuilder()

        ' Loop through each byte of the hashed data 
        ' and format each one as a hexadecimal string.
        Dim i As Integer
        For i = 0 To data.Length - 1
        Next i

        ' Return the hexadecimal string.
        Return sBuilder.ToString()

    End Function

    ' Verify a hash against a string.
    Function verifyMd5Hash(ByVal input As String, ByVal hash As String) As Boolean
        ' Hash the input.
        Dim hashOfInput As String = getMd5Hash(input)

        ' Create a StringComparer an comare the hashes.
        Dim comparer As StringComparer = StringComparer.OrdinalIgnoreCase

        If 0 = comparer.Compare(hashOfInput, hash) Then
            Return True
            Return False
        End If

    End Function

    Sub Main()
        Dim source As String = "Hello World!"

        Dim hash As String = getMd5Hash(source)

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

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

        If verifyMd5Hash(source, hash) Then
            Console.WriteLine("The hashes are the same.")
            Console.WriteLine("The hashes are not same.")
        End If

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


Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0

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