Article
11/17/2011

KeyedHashAlgorithm Class

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Represents the abstract class from which all implementations of keyed hash algorithms must derive.

Inheritance Hierarchy

System.Object
  System.Security.Cryptography.HashAlgorithm
    System.Security.Cryptography.KeyedHashAlgorithm
      System.Security.Cryptography.HMAC

Namespace: System.Security.Cryptography
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
<ComVisibleAttribute(True)> _
Public MustInherit Class KeyedHashAlgorithm _
    Inherits HashAlgorithm

[ComVisibleAttribute(true)]
public abstract class KeyedHashAlgorithm : HashAlgorithm

The KeyedHashAlgorithm type exposes the following members.

Constructors

	Name	Description
	KeyedHashAlgorithm	Initializes a new instance of the KeyedHashAlgorithm class.

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Properties

	Name	Description
	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.)
	Key	Gets or sets the key to use in the hash algorithm.
	OutputBlockSize	When overridden in a derived class, gets the output block size. (Inherited from HashAlgorithm.)

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Methods

	Name	Description
	Clear	Releases all resources used by the HashAlgorithm class. (Inherited from HashAlgorithm.)
	ComputeHash(array<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.)
	ComputeHash(array<Byte[], Int32, Int32)	Computes the hash value for the specified region of the specified byte array. (Inherited from HashAlgorithm.)
	Dispose	Releases the unmanaged resources used by the KeyedHashAlgorithm and optionally releases the managed resources. (Overrides HashAlgorithm.Dispose(Boolean).)
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	HashCore	When overridden in a derived class, routes data written to the object into the hash algorithm for computing the hash. (Inherited from HashAlgorithm.)
	HashFinal	When overridden in a derived class, finalizes the hash computation after the last data is processed by the cryptographic stream object. (Inherited from HashAlgorithm.)
	Initialize	Initializes an implementation of the HashAlgorithm class. (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	Computes the hash value for the specified region of the input byte array and copies the resulting hash value to the specified region of the output byte array. (Inherited from HashAlgorithm.)
	TransformFinalBlock	Computes the hash value for the specified region of the specified byte array. (Inherited from HashAlgorithm.)

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Fields

	Name	Description
	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.
	State	Represents the state of the hash computation. (Inherited from HashAlgorithm.)

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Explicit Interface Implementations

	Name	Description
	IDisposable.Dispose	Releases the unmanaged resources used by the HashAlgorithm and optionally releases the managed resources. (Inherited from HashAlgorithm.)

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Remarks

Hash functions map binary strings of an arbitrary length to small binary strings of a fixed length. A feature of a cryptographic hash function is that it is computationally infeasible to find two distinct inputs that hash to the same value. Small changes to the data result in large, unpredictable changes in the hash.

A keyed hash algorithm is a key-dependent, one-way hash function used as a message authentication code. Only someone who knows the key can verify the hash. Keyed hash algorithms provide authenticity without secrecy.

Hash functions are commonly used with digital signatures and for data integrity. The HMACSHA1 class is an example of a keyed hash algorithm.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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