HMACSHA512 Class

Definition

Computes a Hash-based Message Authentication Code (HMAC) using the SHA512 hash function.

public ref class HMACSHA512 : System::Security::Cryptography::HMAC
[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public class HMACSHA512 : System.Security.Cryptography.HMAC
public class HMACSHA512 : System.Security.Cryptography.HMAC
[System.Runtime.InteropServices.ComVisible(true)]
public class HMACSHA512 : System.Security.Cryptography.HMAC
[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
type HMACSHA512 = class
    inherit HMAC
type HMACSHA512 = class
    inherit HMAC
[<System.Runtime.InteropServices.ComVisible(true)>]
type HMACSHA512 = class
    inherit HMAC
Public Class HMACSHA512
Inherits HMAC
Inheritance
Attributes

Examples

The following example shows how to sign a file by using the HMACSHA512 object and then how to verify the file.

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

// Computes a keyed hash for a source file, creates a target file with the keyed hash
// prepended to the contents of the source file, then decrypts the file and compares
// the source and the decrypted files.
void EncodeFile( array<Byte>^key, String^ sourceFile, String^ destFile )
{
   
   // Initialize the keyed hash object.
   HMACSHA512^ myhmacsha512 = gcnew HMACSHA512( key );
   FileStream^ inStream = gcnew FileStream( sourceFile,FileMode::Open );
   FileStream^ outStream = gcnew FileStream( destFile,FileMode::Create );
   
   // Compute the hash of the input file.
   array<Byte>^hashValue = myhmacsha512->ComputeHash( inStream );
   
   // Reset inStream to the beginning of the file.
   inStream->Position = 0;
   
   // Write the computed hash value to the output file.
   outStream->Write( hashValue, 0, hashValue->Length );
   
   // Copy the contents of the sourceFile to the destFile.
   int bytesRead;
   
   // read 1K at a time
   array<Byte>^buffer = gcnew array<Byte>(1024);
   do
   {
      
      // Read from the wrapping CryptoStream.
      bytesRead = inStream->Read( buffer, 0, 1024 );
      outStream->Write( buffer, 0, bytesRead );
   }
   while ( bytesRead > 0 );

   myhmacsha512->Clear();
   
   // Close the streams
   inStream->Close();
   outStream->Close();
   return;
} // end EncodeFile



// Decrypt the encoded file and compare to original file.
bool DecodeFile( array<Byte>^key, String^ sourceFile )
{
   
   // Initialize the keyed hash object. 
   HMACSHA512^ hmacsha512 = gcnew HMACSHA512( key );
   
   // Create an array to hold the keyed hash value read from the file.
   array<Byte>^storedHash = gcnew array<Byte>(hmacsha512->HashSize / 8);
   
   // Create a FileStream for the source file.
   FileStream^ inStream = gcnew FileStream( sourceFile,FileMode::Open );
   
   // Read in the storedHash.
   inStream->Read( storedHash, 0, storedHash->Length );
   
   // Compute the hash of the remaining contents of the file.
   // The stream is properly positioned at the beginning of the content, 
   // immediately after the stored hash value.
   array<Byte>^computedHash = hmacsha512->ComputeHash( inStream );
   
   // compare the computed hash with the stored value
   bool err = false;
   for ( int i = 0; i < storedHash->Length; i++ )
   {
      if ( computedHash[ i ] != storedHash[ i ] )
      {
         err = true;
      }
   }
   if (err)
        {
            Console::WriteLine("Hash values differ! Encoded file has been tampered with!");
            return false;
        }
        else
        {
            Console::WriteLine("Hash values agree -- no tampering occurred.");
            return true;
        }

} //end DecodeFile


int main()
{
   array<String^>^Fileargs = Environment::GetCommandLineArgs();
   String^ usageText = "Usage: HMACSHA512 inputfile.txt encryptedfile.hsh\nYou must specify the two file names. Only the first file must exist.\n";
   
   //If no file names are specified, write usage text.
   if ( Fileargs->Length < 3 )
   {
      Console::WriteLine( usageText );
   }
   else
   {
      try
      {
         
         // Create a random key using a random number generator. This would be the
         //  secret key shared by sender and receiver.
         array<Byte>^secretkey = gcnew array<Byte>(64);
         
         //RNGCryptoServiceProvider is an implementation of a random number generator.
         RNGCryptoServiceProvider^ rng = gcnew RNGCryptoServiceProvider;
         
         // The array is now filled with cryptographically strong random bytes.
         rng->GetBytes( secretkey );
         
         // Use the secret key to encode the message file.
         EncodeFile( secretkey, Fileargs[ 1 ], Fileargs[ 2 ] );
         
         // Take the encoded file and decode
         DecodeFile( secretkey, Fileargs[ 2 ] );
      }
      catch ( IOException^ e ) 
      {
         Console::WriteLine( "Error: File not found", e );
      }

   }
} //end main
using System;
using System.IO;
using System.Security.Cryptography;

public class HMACSHA512example
{

    public static void Main(string[] Fileargs)
    {
        string dataFile;
        string signedFile;
        //If no file names are specified, create them.
        if (Fileargs.Length < 2)
        {
            dataFile = @"text.txt";
            signedFile = "signedFile.enc";

            if (!File.Exists(dataFile))
            {
                // Create a file to write to.
                using (StreamWriter sw = File.CreateText(dataFile))
                {
                    sw.WriteLine("Here is a message to sign");
                }
            }
        }
        else
        {
            dataFile = Fileargs[0];
            signedFile = Fileargs[1];
        }
        try
        {
            // Create a random key using a random number generator. This would be the
            //  secret key shared by sender and receiver.
            byte[] secretkey = new Byte[64];
            //RNGCryptoServiceProvider is an implementation of a random number generator.
            using (RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider())
            {
                // The array is now filled with cryptographically strong random bytes.
                rng.GetBytes(secretkey);

                // Use the secret key to sign the message file.
                SignFile(secretkey, dataFile, signedFile);

                // Verify the signed file
                VerifyFile(secretkey, signedFile);
            }
        }
        catch (IOException e)
        {
            Console.WriteLine("Error: File not found", e);
        }
    }  //end main
    // Computes a keyed hash for a source file and creates a target file with the keyed hash
    // prepended to the contents of the source file.
    public static void SignFile(byte[] key, String sourceFile, String destFile)
    {
        // Initialize the keyed hash object.
        using (HMACSHA512 hmac = new HMACSHA512(key))
        {
            using (FileStream inStream = new FileStream(sourceFile, FileMode.Open))
            {
                using (FileStream outStream = new FileStream(destFile, FileMode.Create))
                {
                    // Compute the hash of the input file.
                    byte[] hashValue = hmac.ComputeHash(inStream);
                    // Reset inStream to the beginning of the file.
                    inStream.Position = 0;
                    // Write the computed hash value to the output file.
                    outStream.Write(hashValue, 0, hashValue.Length);
                    // Copy the contents of the sourceFile to the destFile.
                    int bytesRead;
                    // read 1K at a time
                    byte[] buffer = new byte[1024];
                    do
                    {
                        // Read from the wrapping CryptoStream.
                        bytesRead = inStream.Read(buffer, 0, 1024);
                        outStream.Write(buffer, 0, bytesRead);
                    } while (bytesRead > 0);
                }
            }
        }
        return;
    } // end SignFile

    // Compares the key in the source file with a new key created for the data portion of the file. If the keys
    // compare the data has not been tampered with.
    public static bool VerifyFile(byte[] key, String sourceFile)
    {
        bool err = false;
        // Initialize the keyed hash object.
        using (HMACSHA512 hmac = new HMACSHA512(key))
        {
            // Create an array to hold the keyed hash value read from the file.
            byte[] storedHash = new byte[hmac.HashSize / 8];
            // Create a FileStream for the source file.
            using (FileStream inStream = new FileStream(sourceFile, FileMode.Open))
            {
                // Read in the storedHash.
                inStream.Read(storedHash, 0, storedHash.Length);
                // Compute the hash of the remaining contents of the file.
                // The stream is properly positioned at the beginning of the content,
                // immediately after the stored hash value.
                byte[] computedHash = hmac.ComputeHash(inStream);
                // compare the computed hash with the stored value

                for (int i = 0; i < storedHash.Length; i++)
                {
                    if (computedHash[i] != storedHash[i])
                    {
                        err = true;
                    }
                }
            }
        }
        if (err)
        {
            Console.WriteLine("Hash values differ! Signed file has been tampered with!");
            return false;
        }
        else
        {
            Console.WriteLine("Hash values agree -- no tampering occurred.");
            return true;
        }
    } //end VerifyFile
} //end class
Imports System.IO
Imports System.Security.Cryptography

Public Class HMACSHA5126example

    Public Shared Sub Main(ByVal Fileargs() As String)
        Dim dataFile As String
        Dim signedFile As String
        'If no file names are specified, create them.
        If Fileargs.Length < 2 Then
            dataFile = "text.txt"
            signedFile = "signedFile.enc"

            If Not File.Exists(dataFile) Then
                ' Create a file to write to.
                Using sw As StreamWriter = File.CreateText(dataFile)
                    sw.WriteLine("Here is a message to sign")
                End Using
            End If

        Else
            dataFile = Fileargs(0)
            signedFile = Fileargs(1)
        End If
        Try
            ' Create a random key using a random number generator. This would be the
            '  secret key shared by sender and receiver.
            Dim secretkey() As Byte = New [Byte](63) {}
            'RNGCryptoServiceProvider is an implementation of a random number generator.
            Using rng As New RNGCryptoServiceProvider()
                ' The array is now filled with cryptographically strong random bytes.
                rng.GetBytes(secretkey)

                ' Use the secret key to encode the message file.
                SignFile(secretkey, dataFile, signedFile)

                ' Take the encoded file and decode
                VerifyFile(secretkey, signedFile)
            End Using
        Catch e As IOException
            Console.WriteLine("Error: File not found", e)
        End Try

    End Sub

    ' Computes a keyed hash for a source file and creates a target file with the keyed hash
    ' prepended to the contents of the source file. 
    Public Shared Sub SignFile(ByVal key() As Byte, ByVal sourceFile As String, ByVal destFile As String)
        ' Initialize the keyed hash object.
        Using myhmac As New HMACSHA512(key)
            Using inStream As New FileStream(sourceFile, FileMode.Open)
                Using outStream As New FileStream(destFile, FileMode.Create)
                    ' Compute the hash of the input file.
                    Dim hashValue As Byte() = myhmac.ComputeHash(inStream)
                    ' Reset inStream to the beginning of the file.
                    inStream.Position = 0
                    ' Write the computed hash value to the output file.
                    outStream.Write(hashValue, 0, hashValue.Length)
                    ' Copy the contents of the sourceFile to the destFile.
                    Dim bytesRead As Integer
                    ' read 1K at a time
                    Dim buffer(1023) As Byte
                    Do
                        ' Read from the wrapping CryptoStream.
                        bytesRead = inStream.Read(buffer, 0, 1024)
                        outStream.Write(buffer, 0, bytesRead)
                    Loop While bytesRead > 0
                End Using
            End Using
        End Using
        Return

    End Sub
    ' end SignFile

    ' Compares the key in the source file with a new key created for the data portion of the file. If the keys 
    ' compare the data has not been tampered with.
    Public Shared Function VerifyFile(ByVal key() As Byte, ByVal sourceFile As String) As Boolean
        Dim err As Boolean = False
        ' Initialize the keyed hash object. 
        Using hmac As New HMACSHA512(key)
            ' Create an array to hold the keyed hash value read from the file.
            Dim storedHash(hmac.HashSize / 8 - 1) As Byte
            ' Create a FileStream for the source file.
            Using inStream As New FileStream(sourceFile, FileMode.Open)
                ' Read in the storedHash.
                inStream.Read(storedHash, 0, storedHash.Length - 1)
                ' Compute the hash of the remaining contents of the file.
                ' The stream is properly positioned at the beginning of the content, 
                ' immediately after the stored hash value.
                Dim computedHash As Byte() = hmac.ComputeHash(inStream)
                ' compare the computed hash with the stored value
                Dim i As Integer
                For i = 0 To storedHash.Length - 2
                    If computedHash(i) <> storedHash(i) Then
                        err = True
                    End If
                Next i
            End Using
        End Using
        If err Then
            Console.WriteLine("Hash values differ! Signed file has been tampered with!")
            Return False
        Else
            Console.WriteLine("Hash values agree -- no tampering occurred.")
            Return True
        End If

    End Function 'VerifyFile 
End Class
'end class

Remarks

HMACSHA512 is a type of keyed hash algorithm that is constructed from the SHA-512 hash function and used as a Hash-based Message Authentication Code (HMAC). The HMAC process mixes a secret key with the message data and hashes the result. The hash value is mixed with the secret key again, and then hashed a second time. The output hash is 512 bits in length.

An HMAC can be used to determine whether a message sent over a nonsecure channel has been tampered with, provided that the sender and receiver share a secret key. The sender computes the hash value for the original data and sends both the original data and hash value as a single message. The receiver recalculates the hash value on the received message and checks that the computed HMAC matches the transmitted HMAC.

If the original and computed hash values match, the message is authenticated. If they do not match, either the data or the hash value has been changed. HMACs provide security against tampering because knowledge of the secret key is required to change the message and reproduce the correct hash value.

HMACSHA512 accepts keys of any size, and produces a hash sequence of length 512 bits.

Constructors

HMACSHA512()

Initializes a new instance of the HMACSHA512 class with a randomly generated key.

HMACSHA512(Byte[])

Initializes a new instance of the HMACSHA512 class with the specified key data.

Fields

HashSizeInBits

The hash size produced by the HMAC SHA512 algorithm, in bits.

HashSizeInBytes

The hash size produced by the HMAC SHA512 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)
KeyValue

The key to use in the hash algorithm.

(Inherited from KeyedHashAlgorithm)
State

Represents the state of the hash computation.

(Inherited from HashAlgorithm)

Properties

BlockSizeValue

Gets or sets the block size to use in the hash value.

(Inherited from HMAC)
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)
HashName

Gets or sets the name of the hash algorithm to use for hashing.

(Inherited from HMAC)
HashSize

Gets the size, in bits, of the computed HMAC.

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)
Key

Gets or sets the key to use in the HMAC calculation.

Key

Gets or sets the key to use in the HMAC calculation.

(Inherited from HMAC)
OutputBlockSize

When overridden in a derived class, gets the output block size.

(Inherited from HashAlgorithm)
ProduceLegacyHmacValues
Obsolete.

Provides a workaround for the .NET Framework 2.0 implementation of the HMACSHA512 algorithm, which is inconsistent with the .NET Framework 2.0 Service Pack 1 implementation.

Methods

Clear()

Releases all resources used by the HashAlgorithm class.

(Inherited from HashAlgorithm)
ComputeHash(Byte[])

Computes the hash value for the specified byte array.

(Inherited from HashAlgorithm)
ComputeHash(Byte[], Int32, Int32)

Computes the hash value for the specified region of 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)
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 HMACSHA512 and optionally releases the managed resources.

Dispose(Boolean)

Releases the unmanaged resources used by the HMAC class when a key change is legitimate and optionally releases the managed resources.

(Inherited from HMAC)
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)

Routes data written to the object into the HMAC algorithm for computing the HMAC.

HashCore(Byte[], Int32, Int32)

When overridden in a derived class, routes data written to the object into the HMAC algorithm for computing the HMAC value.

(Inherited from HMAC)
HashCore(ReadOnlySpan<Byte>)

Routes data written to the object into the HMAC algorithm for computing the HMAC.

HashCore(ReadOnlySpan<Byte>)

Routes data written to the object into the HMAC algorithm for computing the HMAC.

(Inherited from HMAC)
HashData(Byte[], Byte[])

Computes the HMAC of data using the SHA512 algorithm.

HashData(Byte[], Stream)

Computes the HMAC of a stream using the SHA512 algorithm.

HashData(ReadOnlySpan<Byte>, ReadOnlySpan<Byte>)

Computes the HMAC of data using the SHA512 algorithm.

HashData(ReadOnlySpan<Byte>, ReadOnlySpan<Byte>, Span<Byte>)

Computes the HMAC of data using the SHA512 algorithm.

HashData(ReadOnlySpan<Byte>, Stream)

Computes the HMAC of a stream using the SHA512 algorithm.

HashData(ReadOnlySpan<Byte>, Stream, Span<Byte>)

Computes the HMAC of a stream using the SHA512 algorithm.

HashDataAsync(Byte[], Stream, CancellationToken)

Asynchronously computes the HMAC of a stream using the SHA512 algorithm.

HashDataAsync(ReadOnlyMemory<Byte>, Stream, CancellationToken)

Asynchronously computes the HMAC of a stream using the SHA512 algorithm.

HashDataAsync(ReadOnlyMemory<Byte>, Stream, Memory<Byte>, CancellationToken)

Asynchronously computes the HMAC of a stream using the SHA512 algorithm.

HashFinal()

Finalizes the HMAC computation after the last data is processed by the algorithm.

HashFinal()

When overridden in a derived class, finalizes the HMAC computation after the last data is processed by the algorithm.

(Inherited from HMAC)
Initialize()

Resets the hash algorithm to its initial state.

Initialize()

Initializes an instance of the default implementation of HMAC.

(Inherited from HMAC)
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>, ReadOnlySpan<Byte>, Span<Byte>, Int32)

Attempts to compute the HMAC of data using the SHA512 algorithm.

TryHashFinal(Span<Byte>, Int32)

Attempts to finalize the HMAC computation after the last data is processed by the HMAC algorithm.

TryHashFinal(Span<Byte>, Int32)

Attempts to finalize the HMAC computation after the last data is processed by the HMAC algorithm.

(Inherited from HMAC)

Explicit Interface Implementations

IDisposable.Dispose()

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

(Inherited from HashAlgorithm)

Applies to

See also