SHA256 Class

Definition

Namespace:

System.Security.Cryptography

Assembly:

System.Security.Cryptography.dll

Source:

SHA256.cs

Computes the SHA256 hash for the input data.

public ref class SHA256 abstract : System::Security::Cryptography::HashAlgorithm

public abstract class SHA256 : System.Security.Cryptography.HashAlgorithm

type SHA256 = class
    inherit HashAlgorithm

Public MustInherit Class SHA256
Inherits HashAlgorithm

Inheritance

Object

HashAlgorithm

SHA256

Derived

System.Security.Cryptography.SHA256Cng

System.Security.Cryptography.SHA256CryptoServiceProvider

System.Security.Cryptography.SHA256Managed

Examples

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

using namespace System;
using namespace System::IO;
using namespace System::Security::Cryptography;

// Print the byte array in a readable format.
void PrintByteArray( array<Byte>^array )
{
   int i;
   for ( i = 0; i < array->Length; i++ )
   {
      Console::Write( String::Format( "{0:X2}", array[ i ] ) );
      if ( (i % 4) == 3 )
            Console::Write( " " );

   }
   Console::WriteLine();
}

int main()
{
   array<String^>^args = Environment::GetCommandLineArgs();
   if ( args->Length < 2 )
   {
      Console::WriteLine( "Usage: hashdir <directory>" );
      return 0;
   }

   try
   {

      // Create a DirectoryInfo object representing the specified directory.
      DirectoryInfo^ dir = gcnew DirectoryInfo( args[ 1 ] );

      // Get the FileInfo objects for every file in the directory.
      array<FileInfo^>^files = dir->GetFiles();

      // Initialize a SHA256 hash object.
      SHA256 ^ mySHA256 = SHA256Managed::Create();
      array<Byte>^hashValue;

      // Compute and print the hash values for each file in directory.
      System::Collections::IEnumerator^ myEnum = files->GetEnumerator();
      while ( myEnum->MoveNext() )
      {
         FileInfo^ fInfo = safe_cast<FileInfo^>(myEnum->Current);

         // Create a fileStream for the file.
         FileStream^ fileStream = fInfo->Open( FileMode::Open );

         // Compute the hash of the fileStream.
         hashValue = mySHA256->ComputeHash( fileStream );

         // Write the name of the file to the Console.
         Console::Write( "{0}: ", fInfo->Name );

         // Write the hash value to the Console.
         PrintByteArray( hashValue );

         // Close the file.
         fileStream->Close();
      }
      return 0;
   }
   catch ( DirectoryNotFoundException^ ) 
   {
      Console::WriteLine( "Error: The directory specified could not be found." );
   }
   catch ( IOException^ ) 
   {
      Console::WriteLine( "Error: A file in the directory could not be accessed." );
   }

}

using System;
using System.IO;
using System.Security.Cryptography;

public class HashDirectory
{
    public static void Main(string[] args)
    {
        if (args.Length < 1)
        {
            Console.WriteLine("No directory selected.");
            return;
        }

        string directory = args[0];
        if (Directory.Exists(directory))
        {
            // Create a DirectoryInfo object representing the specified directory.
            var dir = new DirectoryInfo(directory);
            // Get the FileInfo objects for every file in the directory.
            FileInfo[] files = dir.GetFiles();
            // Initialize a SHA256 hash object.
            using (SHA256 mySHA256 = SHA256.Create())
            {
                // Compute and print the hash values for each file in directory.
                foreach (FileInfo fInfo in files)
                {
                    using (FileStream fileStream = fInfo.Open(FileMode.Open))
                    {
                        try
                        {
                            // Create a fileStream for the file.
                            // Be sure it's positioned to the beginning of the stream.
                            fileStream.Position = 0;
                            // Compute the hash of the fileStream.
                            byte[] hashValue = mySHA256.ComputeHash(fileStream);
                            // Write the name and hash value of the file to the console.
                            Console.Write($"{fInfo.Name}: ");
                            PrintByteArray(hashValue);
                        }
                        catch (IOException e)
                        {
                            Console.WriteLine($"I/O Exception: {e.Message}");
                        }
                        catch (UnauthorizedAccessException e)
                        {
                            Console.WriteLine($"Access Exception: {e.Message}");
                        }
                    }
                }
            }
        }
        else
        {
            Console.WriteLine("The directory specified could not be found.");
        }
    }

    // Display the byte array in a readable format.
    public static void PrintByteArray(byte[] array)
    {
        for (int i = 0; i < array.Length; i++)
        {
            Console.Write($"{array[i]:X2}");
            if ((i % 4) == 3) Console.Write(" ");
        }
        Console.WriteLine();
    }
}

Imports System.IO
Imports System.Security.Cryptography

Public Module HashDirectory

    Public Sub Main(ByVal args() As String)
        If args.Length < 1 Then
            Console.WriteLine("No directory selected")
            Return
        End If

        Dim targetDirectory As String = args(0)
        If Directory.Exists(targetDirectory) Then
            ' Create a DirectoryInfo object representing the specified directory.
            Dim dir As New DirectoryInfo(targetDirectory)
            ' Get the FileInfo objects for every file in the directory.
            Dim files As FileInfo() = dir.GetFiles()
            ' Initialize a SHA256 hash object.
            Using mySHA256 As SHA256 = SHA256.Create()
                ' Compute and print the hash values for each file in directory.
                For Each fInfo  As FileInfo In files
                    Try
                        ' Create a fileStream for the file.
                        Dim 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.
                        Dim hashValue() As Byte = 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()
                    Catch e As IOException
                        Console.WriteLine($"I/O Exception: {e.Message}")
                    Catch e As UnauthorizedAccessException 
                        Console.WriteLine($"Access Exception: {e.Message}")
                    End Try    
                Next 
            End Using
        Else
           Console.WriteLine("The directory specified could not be found.")
        End If
    End Sub

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

    End Sub 
End Module

Remarks

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.

Constructors

SHA256()

Initializes a new instance of SHA256.

Fields

HashSizeInBits	The hash size produced by the SHA256 algorithm, in bits.
HashSizeInBytes	The hash size produced by the SHA256 algorithm, in bytes.
HashSizeValue	Represents the size, in bits, of the computed hash code. (Inherited from HashAlgorithm)
HashValue	Represents the value of the computed hash code. (Inherited from HashAlgorithm)
State	Represents the state of the hash computation. (Inherited from HashAlgorithm)

Properties

CanReuseTransform	Gets a value indicating whether the current transform can be reused. (Inherited from HashAlgorithm)
CanTransformMultipleBlocks	When overridden in a derived class, gets a value indicating whether multiple blocks can be transformed. (Inherited from HashAlgorithm)
Hash	Gets the value of the computed hash code. (Inherited from HashAlgorithm)
HashSize	Gets the size, in bits, of the computed hash code. (Inherited from HashAlgorithm)
InputBlockSize	When overridden in a derived class, gets the input block size. (Inherited from HashAlgorithm)
OutputBlockSize	When overridden in a derived class, gets the output block size. (Inherited from HashAlgorithm)

Methods

Clear()	Releases all resources used by the HashAlgorithm class. (Inherited from HashAlgorithm)
ComputeHash(Byte[], Int32, Int32)	Computes the hash value for the specified region of the specified byte array. (Inherited from HashAlgorithm)
ComputeHash(Byte[])	Computes the hash value for the specified byte array. (Inherited from HashAlgorithm)
ComputeHash(Stream)	Computes the hash value for the specified Stream object. (Inherited from HashAlgorithm)
ComputeHashAsync(Stream, CancellationToken)	Asynchronously computes the hash value for the specified Stream object. (Inherited from HashAlgorithm)
Create()	Creates an instance of the default implementation of SHA256.
Create(String)	Obsolete. Creates an instance of a specified implementation of SHA256.
Dispose()	Releases all resources used by the current instance of the HashAlgorithm class. (Inherited from HashAlgorithm)
Dispose(Boolean)	Releases the unmanaged resources used by the HashAlgorithm and optionally releases the managed resources. (Inherited from HashAlgorithm)
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
HashCore(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)
HashCore(ReadOnlySpan<Byte>)	Routes data written to the object into the hash algorithm for computing the hash. (Inherited from HashAlgorithm)
HashData(Byte[])	Computes the hash of data using the SHA256 algorithm.
HashData(ReadOnlySpan<Byte>, Span<Byte>)	Computes the hash of data using the SHA256 algorithm.
HashData(ReadOnlySpan<Byte>)	Computes the hash of data using the SHA256 algorithm.
HashData(Stream, Span<Byte>)	Computes the hash of a stream using the SHA256 algorithm.
HashData(Stream)	Computes the hash of a stream using the SHA256 algorithm.
HashDataAsync(Stream, CancellationToken)	Asynchronously computes the hash of a stream using the SHA256 algorithm.
HashDataAsync(Stream, Memory<Byte>, CancellationToken)	Asynchronously computes the hash of a stream using the SHA256 algorithm.
HashFinal()	When overridden in a derived class, finalizes the hash computation after the last data is processed by the cryptographic hash algorithm. (Inherited from HashAlgorithm)
Initialize()	Resets the hash algorithm to its initial state. (Inherited from HashAlgorithm)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)
TransformBlock(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)
TransformFinalBlock(Byte[], Int32, Int32)	Computes the hash value for the specified region of the specified byte array. (Inherited from HashAlgorithm)
TryComputeHash(ReadOnlySpan<Byte>, Span<Byte>, Int32)	Attempts to compute the hash value for the specified byte array. (Inherited from HashAlgorithm)
TryHashData(ReadOnlySpan<Byte>, Span<Byte>, Int32)	Attempts to compute the hash of data using the SHA256 algorithm.
TryHashFinal(Span<Byte>, Int32)	Attempts to finalize the hash computation after the last data is processed by the hash algorithm. (Inherited from HashAlgorithm)

See also

• Cryptographic Services