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HashAlgorithm Class

Represents the base class from which all implementations of cryptographic hash algorithms must derive.

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

'Declaration
<ComVisibleAttribute(True)> _
Public MustInherit Class HashAlgorithm _
	Implements ICryptoTransform, IDisposable

The HashAlgorithm type exposes the following members.

  NameDescription
Protected methodHashAlgorithmInitializes a new instance of the HashAlgorithm class.
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  NameDescription
Public propertyCanReuseTransformGets a value indicating whether the current transform can be reused.
Public propertyCanTransformMultipleBlocksWhen overridden in a derived class, gets a value indicating whether multiple blocks can be transformed.
Public propertyHashGets the value of the computed hash code.
Public propertyHashSizeGets the size, in bits, of the computed hash code.
Public propertyInputBlockSizeWhen overridden in a derived class, gets the input block size.
Public propertyOutputBlockSizeWhen overridden in a derived class, gets the output block size.
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  NameDescription
Public methodClearReleases all resources used by the HashAlgorithm class.
Public methodComputeHash(Byte())Computes the hash value for the specified byte array.
Public methodComputeHash(Stream)Computes the hash value for the specified Stream object.
Public methodComputeHash(Byte(), Int32, Int32)Computes the hash value for the specified region of the specified byte array.
Public methodStatic memberCreateCreates an instance of the default implementation of a hash algorithm.
Public methodStatic memberCreate(String)Creates an instance of the specified implementation of a hash algorithm.
Public methodDisposeReleases all resources used by the current instance of the HashAlgorithm class.
Protected methodDispose(Boolean)Releases the unmanaged resources used by the HashAlgorithm and optionally releases the managed resources.
Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodHashCoreWhen overridden in a derived class, routes data written to the object into the hash algorithm for computing the hash.
Protected methodHashFinalWhen overridden in a derived class, finalizes the hash computation after the last data is processed by the cryptographic stream object.
Public methodInitializeInitializes an implementation of the HashAlgorithm class.
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Public methodTransformBlockComputes 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.
Public methodTransformFinalBlockComputes the hash value for the specified region of the specified byte array.
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  NameDescription
Protected fieldHashSizeValueRepresents the size, in bits, of the computed hash code.
Protected fieldHashValueRepresents the value of the computed hash code.
Protected fieldStateRepresents the state of the hash computation.
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Hash functions are fundamental to modern cryptography. These functions map binary strings of an arbitrary length to small binary strings of a fixed length, known as hash values. A cryptographic hash function has the property that it is computationally infeasible to find two distinct inputs that hash to the same value. Hash functions are commonly used with digital signatures and for data integrity.

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 the corresponding data also matches. Small changes to the data result in large unpredictable changes in the hash.

Notes to Inheritors

When you inherit from the HashAlgorithm class, you must override the following members: HashCore and HashFinal.

The following code example computes the SHA1CryptoServiceProvider hash for an array. This example assumes that there is a predefined byte array dataArray[]. SHA1CryptoServiceProvider is a derived class of HashAlgorithm.


Dim sha As New SHA1CryptoServiceProvider()
Dim result As Byte() = sha.ComputeHash(dataArray)


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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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