HashAlgorithm Class (System.Security.Cryptography)

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

HashAlgorithm Class

Updated: November 2007

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

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

Syntax

Visual Basic (Declaration)

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

Visual Basic (Usage)

Dim instance As HashAlgorithm

[ComVisibleAttribute(true)]
public abstract class HashAlgorithm : ICryptoTransform, 
    IDisposable

Visual C++

[ComVisibleAttribute(true)]
public ref class HashAlgorithm abstract : ICryptoTransform, 
    IDisposable

/** @attribute ComVisibleAttribute(true) */
public abstract class HashAlgorithm implements ICryptoTransform, 
    IDisposable

JScript

public abstract class HashAlgorithm implements ICryptoTransform, IDisposable

Remarks

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.

Examples

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.

Visual Basic

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

HashAlgorithm sha = new SHA1CryptoServiceProvider();
byte[] result = sha.ComputeHash(dataArray);

Visual C++

HashAlgorithm^ sha = gcnew SHA1CryptoServiceProvider;
array<Byte>^ result = sha->ComputeHash( dataArray );

HashAlgorithm sha = new SHA1CryptoServiceProvider();
ubyte result[] = sha.ComputeHash(dataArray);

Inheritance Hierarchy

System..::.Object
  System.Security.Cryptography..::.HashAlgorithm
    System.Security.Cryptography..::.KeyedHashAlgorithm
    System.Security.Cryptography..::.MD5
    System.Security.Cryptography..::.RIPEMD160
    System.Security.Cryptography..::.SHA1
    System.Security.Cryptography..::.SHA256
    System.Security.Cryptography..::.SHA384
    System.Security.Cryptography..::.SHA512

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.

Platforms

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

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

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