SHA256 Class (System.Security.Cryptography) (2024)

Definition

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

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

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

type SHA256 = class inherit HashAlgorithm

[<System.Runtime.InteropServices.ComVisible(true)>]type SHA256 = class inherit HashAlgorithm

Public MustInherit Class SHA256Inherits HashAlgorithm

Inheritance

Object

HashAlgorithm

SHA256

Derived

System.Security.Cryptography.SHA256Cng

System.Security.Cryptography.SHA256CryptoServiceProvider

System.Security.Cryptography.SHA256Managed

Attributes

ComVisibleAttribute

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.IOImports System.Security.CryptographyPublic 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

Fields

Properties

Methods

Explicit Interface Implementations

Applies to

See also

• Cryptographic Services