# KeyedHashAlgorithmKeyedHashAlgorithmKeyedHashAlgorithmKeyedHashAlgorithm Class

## Definição

Representa a classe base abstrata da qual todas as implementações de algoritmo de hash inseridas devem derivar.Represents the abstract class from which all implementations of keyed hash algorithms must derive.

``public ref class KeyedHashAlgorithm abstract : System::Security::Cryptography::HashAlgorithm``
``````[System.Runtime.InteropServices.ComVisible(true)]
public abstract class KeyedHashAlgorithm : System.Security.Cryptography.HashAlgorithm``````
``````type KeyedHashAlgorithm = class
inherit HashAlgorithm``````
``````Public MustInherit Class KeyedHashAlgorithm
Inherits HashAlgorithm``````
Herança
KeyedHashAlgorithmKeyedHashAlgorithmKeyedHashAlgorithmKeyedHashAlgorithm
Atributos

## Exemplos

O exemplo de código a seguir demonstra como derivar a KeyedHashAlgorithm classe.The following code example demonstrates how to derive from the KeyedHashAlgorithm class.

``````using System;
using System.Security.Cryptography;

public class TestHMACMD5
{
static private void PrintByteArray(Byte[] arr)
{
int i;
Console.WriteLine("Length: " + arr.Length);
for (i = 0; i < arr.Length; i++)
{
Console.Write("{0:X}", arr[i]);
Console.Write("    ");
if ((i + 9) % 8 == 0) Console.WriteLine();
}
if (i % 8 != 0) Console.WriteLine();
}
public static void Main()
{
// Create a key.
byte[] key1 = { 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b };
// Pass the key to the constructor of the HMACMD5 class.
HMACMD5 hmac1 = new HMACMD5(key1);

// Create another key.
byte[] key2 = System.Text.Encoding.ASCII.GetBytes("KeyString");
// Pass the key to the constructor of the HMACMD5 class.
HMACMD5 hmac2 = new HMACMD5(key2);

// Encode a string into a byte array, create a hash of the array,
// and print the hash to the screen.
byte[] data1 = System.Text.Encoding.ASCII.GetBytes("Hi There");
PrintByteArray(hmac1.ComputeHash(data1));

// Encode a string into a byte array, create a hash of the array,
// and print the hash to the screen.
byte[] data2 = System.Text.Encoding.ASCII.GetBytes("This data will be hashed.");
PrintByteArray(hmac2.ComputeHash(data2));
}
}
public class HMACMD5 : KeyedHashAlgorithm
{
private MD5 hash1;
private MD5 hash2;
private bool bHashing = false;

private byte[] rgbInner = new byte[64];
private byte[] rgbOuter = new byte[64];

public HMACMD5(byte[] rgbKey)
{
HashSizeValue = 128;
// Create the hash algorithms.
hash1 = MD5.Create();
hash2 = MD5.Create();
// Get the key.
if (rgbKey.Length > 64)
{
KeyValue = hash1.ComputeHash(rgbKey);
// No need to call Initialize; ComputeHash does it automatically.
}
else
{
KeyValue = (byte[])rgbKey.Clone();
}
// Compute rgbInner and rgbOuter.
int i = 0;
for (i = 0; i < 64; i++)
{
rgbInner[i] = 0x36;
rgbOuter[i] = 0x5C;
}
for (i = 0; i < KeyValue.Length; i++)
{
rgbInner[i] ^= KeyValue[i];
rgbOuter[i] ^= KeyValue[i];
}
}

public override byte[] Key
{
get { return (byte[])KeyValue.Clone(); }
set
{
if (bHashing)
{
throw new Exception("Cannot change key during hash operation");
}
if (value.Length > 64)
{
KeyValue = hash1.ComputeHash(value);
// No need to call Initialize; ComputeHash does it automatically.
}
else
{
KeyValue = (byte[])value.Clone();
}
// Compute rgbInner and rgbOuter.
int i = 0;
for (i = 0; i < 64; i++)
{
rgbInner[i] = 0x36;
rgbOuter[i] = 0x5C;
}
for (i = 0; i < KeyValue.Length; i++)
{
rgbInner[i] ^= KeyValue[i];
rgbOuter[i] ^= KeyValue[i];
}
}
}
public override void Initialize()
{
hash1.Initialize();
hash2.Initialize();
bHashing = false;
}
protected override void HashCore(byte[] rgb, int ib, int cb)
{
if (bHashing == false)
{
hash1.TransformBlock(rgbInner, 0, 64, rgbInner, 0);
bHashing = true;
}
hash1.TransformBlock(rgb, ib, cb, rgb, ib);
}

protected override byte[] HashFinal()
{
if (bHashing == false)
{
hash1.TransformBlock(rgbInner, 0, 64, rgbInner, 0);
bHashing = true;
}
// Finalize the original hash.
hash1.TransformFinalBlock(new byte[0], 0, 0);
// Write the outer array.
hash2.TransformBlock(rgbOuter, 0, 64, rgbOuter, 0);
// Write the inner hash and finalize the hash.
hash2.TransformFinalBlock(hash1.Hash, 0, hash1.Hash.Length);
bHashing = false;
return hash2.Hash;
}
}
``````
``````Imports System
Imports System.Security.Cryptography
_

Public Class TestHMACMD5

Private Shared Sub PrintByteArray(ByVal arr() As [Byte])
Dim i As Integer
Console.WriteLine(("Length: " + arr.Length.ToString()))
For i = 0 To arr.Length - 1
Console.Write("{0:X}", arr(i))
Console.Write("    ")
If (i + 9) Mod 8 = 0 Then
Console.WriteLine()
End If
Next i
If i Mod 8 <> 0 Then
Console.WriteLine()
End If
End Sub

Public Shared Sub Main()
' Create a key.
Dim key1 As Byte() = {&HB, &HB, &HB, &HB, &HB, &HB, &HB, &HB, &HB, &HB, &HB, &HB, &HB, &HB, &HB, &HB}
' Pass the key to the constructor of the HMACMD5 class.
Dim hmac1 As New HMACMD5(key1)

' Create another key.
Dim key2 As Byte() = System.Text.Encoding.ASCII.GetBytes("KeyString")
' Pass the key to the constructor of the HMACMD5 class.
Dim hmac2 As New HMACMD5(key2)

' Encode a string into a byte array, create a hash of the array,
' and print the hash to the screen.
Dim data1 As Byte() = System.Text.Encoding.ASCII.GetBytes("Hi There")
PrintByteArray(hmac1.ComputeHash(data1))

' Encode a string into a byte array, create a hash of the array,
' and print the hash to the screen.
Dim data2 As Byte() = System.Text.Encoding.ASCII.GetBytes("This data will be hashed.")
PrintByteArray(hmac2.ComputeHash(data2))
End Sub
End Class
_

Public Class HMACMD5
Inherits KeyedHashAlgorithm
Private hash1 As MD5
Private hash2 As MD5
Private bHashing As Boolean = False

Private rgbInner(64) As Byte
Private rgbOuter(64) As Byte

Public Sub New(ByVal rgbKey() As Byte)
HashSizeValue = 128
' Create the hash algorithms.
hash1 = MD5.Create()
hash2 = MD5.Create()
' Get the key.
If rgbKey.Length > 64 Then
KeyValue = hash1.ComputeHash(rgbKey)
' No need to call Initialize; ComputeHash does it automatically.
Else
KeyValue = CType(rgbKey.Clone(), Byte())
End If
' Compute rgbInner and rgbOuter.
Dim i As Integer = 0
For i = 0 To 63
rgbInner(i) = &H36
rgbOuter(i) = &H5C
Next i
i = 0
For i = 0 To KeyValue.Length - 1
rgbInner(i) = rgbInner(i) Xor KeyValue(i)
rgbOuter(i) = rgbOuter(i) Xor KeyValue(i)
Next i
End Sub

Public Overrides Property Key() As Byte()
Get
Return CType(KeyValue.Clone(), Byte())
End Get
Set(ByVal Value As Byte())
If bHashing Then
Throw New Exception("Cannot change key during hash operation")
End If
If value.Length > 64 Then
KeyValue = hash1.ComputeHash(value)
' No need to call Initialize; ComputeHash does it automatically.
Else
KeyValue = CType(value.Clone(), Byte())
End If
' Compute rgbInner and rgbOuter.
Dim i As Integer = 0
For i = 0 To 63
rgbInner(i) = &H36
rgbOuter(i) = &H5C
Next i
For i = 0 To KeyValue.Length - 1
rgbInner(i) ^= KeyValue(i)
rgbOuter(i) ^= KeyValue(i)
Next i
End Set
End Property

Public Overrides Sub Initialize()
hash1.Initialize()
hash2.Initialize()
bHashing = False
End Sub

Protected Overrides Sub HashCore(ByVal rgb() As Byte, ByVal ib As Integer, ByVal cb As Integer)
If bHashing = False Then
hash1.TransformBlock(rgbInner, 0, 64, rgbInner, 0)
bHashing = True
End If
hash1.TransformBlock(rgb, ib, cb, rgb, ib)
End Sub

Protected Overrides Function HashFinal() As Byte()
If bHashing = False Then
hash1.TransformBlock(rgbInner, 0, 64, rgbInner, 0)
bHashing = True
End If
' Finalize the original hash.
hash1.TransformFinalBlock(New Byte(0) {}, 0, 0)
' Write the outer array.
hash2.TransformBlock(rgbOuter, 0, 64, rgbOuter, 0)
' Write the inner hash and finalize the hash.
hash2.TransformFinalBlock(hash1.Hash, 0, hash1.Hash.Length)
bHashing = False
Return hash2.Hash
End Function
End Class
``````

## Comentários

Hash funções mapa cadeias de caracteres binárias de um comprimento arbitrário para pequenas cadeias de caracteres binárias de comprimento fixo.Hash functions map binary strings of an arbitrary length to small binary strings of a fixed length. Uma função de hash criptográfico tem a propriedade que é impraticável para encontrar duas entradas distintas esse hash com o mesmo valor.A cryptographic hash function has the property that it is computationally infeasible to find two distinct inputs that hash to the same value. Pequenas alterações aos dados resultar em grandes, imprevisíveis alterações no hash.Small changes to the data result in large, unpredictable changes in the hash.

Um algoritmo de hash com chave é uma função de hash unidirecional dependente de chave usada como um código de autenticação de mensagem.A keyed hash algorithm is a key-dependent, one-way hash function used as a message authentication code. Somente alguém que sabe que a chave pode verificar o hash.Only someone who knows the key can verify the hash. Algoritmos de hash com chave fornecem autenticidade sem sigilo.Keyed hash algorithms provide authenticity without secrecy.

Funções de hash são usadas com assinaturas digitais e integridade dos dados.Hash functions are commonly used with digital signatures and for data integrity. O HMACSHA1 classe é um exemplo de um algoritmo de hash com chave.The HMACSHA1 class is an example of a keyed hash algorithm.

## Construtores

 KeyedHashAlgorithm() KeyedHashAlgorithm() KeyedHashAlgorithm() KeyedHashAlgorithm() Inicializa uma nova instância da classe KeyedHashAlgorithm.Initializes a new instance of the KeyedHashAlgorithm class.

## Campos

 HashSizeValue HashSizeValue HashSizeValue HashSizeValue Representa o tamanho, em bits, do código hash calculado.Represents the size, in bits, of the computed hash code. (Inherited from HashAlgorithm) HashValue HashValue HashValue HashValue Representa o valor do código hash computado.Represents the value of the computed hash code. (Inherited from HashAlgorithm) KeyValue KeyValue KeyValue KeyValue A chave a ser usada no algoritmo de hash.The key to use in the hash algorithm. State State State State Representa o estado do cálculo de hash.Represents the state of the hash computation. (Inherited from HashAlgorithm)

 CanReuseTransform CanReuseTransform CanReuseTransform CanReuseTransform Obtém um valor que indica se a transformação atual pode ser reutilizada.Gets a value indicating whether the current transform can be reused. (Inherited from HashAlgorithm) CanTransformMultipleBlocks CanTransformMultipleBlocks CanTransformMultipleBlocks CanTransformMultipleBlocks Quando substituído em uma classe derivada, obtém um valor que indica se vários blocos podem ser transformados.When overridden in a derived class, gets a value indicating whether multiple blocks can be transformed. (Inherited from HashAlgorithm) Hash Hash Hash Hash Obtém o valor do código hash computado.Gets the value of the computed hash code. (Inherited from HashAlgorithm) HashSize HashSize HashSize HashSize Obtém o tamanho, em bits, do código hash computado.Gets the size, in bits, of the computed hash code. (Inherited from HashAlgorithm) InputBlockSize InputBlockSize InputBlockSize InputBlockSize Quando substituído em uma classe derivada, obtém o tamanho do bloco de entrada.When overridden in a derived class, gets the input block size. (Inherited from HashAlgorithm) Key Key Key Key Obtém ou define a chave a ser usada no algoritmo de hash.Gets or sets the key to use in the hash algorithm. OutputBlockSize OutputBlockSize OutputBlockSize OutputBlockSize Quando substituído em uma classe derivada, obtém o tamanho do bloco de saída.When overridden in a derived class, gets the output block size. (Inherited from HashAlgorithm)