SHA256 Class

 

Computes the SHA256 hash for the input data.

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


<ComVisibleAttribute(True)>
Public MustInherit Class SHA256
	Inherits HashAlgorithm

NameDescription
System_CAPS_protmethodSHA256()

Initializes a new instance of SHA256.

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_pubmethodSystem_CAPS_staticCreate()

Creates an instance of the default implementation of SHA256.

System_CAPS_pubmethodSystem_CAPS_staticCreate(String)

Creates an instance of a specified implementation of SHA256.

System_CAPS_pubmethodDispose()

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

System_CAPS_protmethodDispose(Boolean)

Releases the unmanaged resources used by the HashAlgorithm and optionally releases the managed resources.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(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_protmethodHashCore(Byte(), Int32, Int32)

When overridden in a derived class, routes data written to the object into the hash algorithm for computing the hash.(Inherited from HashAlgorithm.)

System_CAPS_protmethodHashFinal()

When overridden in a derived class, finalizes the hash computation after the last data is processed by the cryptographic stream object.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodInitialize()

Initializes an implementation of the HashAlgorithm class.(Inherited from HashAlgorithm.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

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_protfieldHashSizeValue

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

System_CAPS_protfieldHashValue

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

System_CAPS_protfieldState

Represents the state of the hash computation.(Inherited from HashAlgorithm.)

The hash is used as a unique value of fixed size representing a large amount of data. Hashes of two sets of data should match if and only if the corresponding data also matches. Small changes to the data result in large unpredictable changes in the hash.

The hash size for the SHA256 algorithm is 256 bits.

This is an abstract class. The only implementation of this class is SHA256Managed.

The following example calculates the SHA-256 hash for all files in a directory.

Imports System
Imports System.IO
Imports System.Security.Cryptography
Imports System.Windows.Forms

Public Class HashDirectory

    Public Shared Sub Main(ByVal args() As String)
        Dim directory As String
        If args.Length < 1 Then
            Dim fdb As New FolderBrowserDialog
            Dim dr As DialogResult = fdb.ShowDialog()
            If (dr = DialogResult.OK) Then
                directory = fdb.SelectedPath
            Else
                Console.WriteLine("No directory selected")
                Return
            End If
        Else
            directory = args(0)
        End If
        Try
            ' Create a DirectoryInfo object representing the specified directory.
            Dim dir As New DirectoryInfo(directory)
            ' Get the FileInfo objects for every file in the directory.
            Dim files As FileInfo() = dir.GetFiles()
            ' Initialize a SHA256 hash object.
            Dim mySHA256 As SHA256 = SHA256Managed.Create()
            Dim hashValue() As Byte
            ' Compute and print the hash values for each file in directory.
            Dim fInfo As FileInfo
            For Each fInfo In files
                ' Create a fileStream for the file.
                Dim fileStream As FileStream = fInfo.Open(FileMode.Open)
                ' Be sure it's positioned to the beginning of the stream.
                fileStream.Position = 0
                ' Compute the hash of the fileStream.
                hashValue = mySHA256.ComputeHash(fileStream)
                ' Write the name of the file to the Console.
                Console.Write(fInfo.Name + ": ")
                ' Write the hash value to the Console.
                PrintByteArray(hashValue)
                ' Close the file.
                fileStream.Close()
            Next fInfo
            Return
        Catch DExc As DirectoryNotFoundException
            Console.WriteLine("Error: The directory specified could not be found.")
        Catch IOExc As IOException
            Console.WriteLine("Error: A file in the directory could not be accessed.")
        End Try

    End Sub

    ' Print the byte array in a readable format.
    Public Shared Sub PrintByteArray(ByVal array() As Byte)
        Dim i As Integer
        For i = 0 To array.Length - 1
            Console.Write(String.Format("{0:X2}", array(i)))
            If i Mod 4 = 3 Then
                Console.Write(" ")
            End If
        Next i
        Console.WriteLine()

    End Sub 'PrintByteArray
End Class

.NET Framework
Available since 1.1
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0

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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