SHA256 Class

Definition

Computes the SHA256 hash for the input data.

public abstract class SHA256 : System.Security.Cryptography.HashAlgorithm
[System.Runtime.InteropServices.ComVisible(true)]
public abstract class SHA256 : System.Security.Cryptography.HashAlgorithm
Inheritance
Derived
Attributes

Examples

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

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();
    }
}

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)

Explicit Interface Implementations

IDisposable.Dispose()

Releases the unmanaged resources used by the HashAlgorithm and optionally releases the managed resources.

(Inherited from HashAlgorithm)

Applies to

Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.3, 1.4, 1.6, 2.0, 2.1

See also