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HashAlgorithm.ComputeHash Method (Byte())

Computes the hash value for the specified byte array.

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

'Declaration
Public Function ComputeHash ( _
	buffer As Byte() _
) As Byte()

Parameters

buffer
Type: System.Byte()
The input to compute the hash code for.

Return Value

Type: System.Byte()
The computed hash code.

ExceptionCondition
ArgumentNullException

buffer is Nothing.

ObjectDisposedException

The object has already been disposed.

The size of the hash value depends on the hash algorithm it is computed for. For example, the size of the hash for the HMACSHA384 algorithm is 384 bits, and the size of the hash for the HMACSHA256 algorithm is 256 bits. You can obtain the size of the hash in bits by calling the HashSize property. For more information about hash codes, see Ensuring Data Integrity with Hash Codes.

The following 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


Class Program

    Shared Sub Main(ByVal args() As String)
        Dim [source] As String = "Hello World!"
        Using md5Hash As MD5 = MD5.Create()

            Dim hash As String = GetMd5Hash(md5Hash, source)

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

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

            If VerifyMd5Hash(md5Hash, [source], hash) Then
                Console.WriteLine("The hashes are the same.")
            Else
                Console.WriteLine("The hashes are not same.")
            End If
        End Using
    End Sub 'Main



    Shared Function GetMd5Hash(ByVal md5Hash As MD5, ByVal input As String) As String

        ' Convert the input string to a byte array and compute the hash.
        Dim data As Byte() = md5Hash.ComputeHash(Encoding.UTF8.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
            sBuilder.Append(data(i).ToString("x2"))
        Next i

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

    End Function 'GetMd5Hash


    ' Verify a hash against a string.
    Shared Function VerifyMd5Hash(ByVal md5Hash As MD5, ByVal input As String, ByVal hash As String) As Boolean
        ' Hash the input.
        Dim hashOfInput As String = GetMd5Hash(md5Hash, input)

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

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

    End Function 'VerifyMd5Hash
End Class 'Program 
' 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.
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