HashAlgorithm Class

Definition

Namespace:

System.Security.Cryptography

Assembly:

System.Security.Cryptography.dll

Source:

HashAlgorithm.cs

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

public ref class HashAlgorithm abstract : IDisposable, System::Security::Cryptography::ICryptoTransform

public abstract class HashAlgorithm : IDisposable, System.Security.Cryptography.ICryptoTransform

type HashAlgorithm = class
    interface IDisposable
    interface ICryptoTransform

Public MustInherit Class HashAlgorithm
Implements ICryptoTransform, IDisposable

Inheritance

Object

HashAlgorithm

Derived

System.Security.Cryptography.KeyedHashAlgorithm

System.Security.Cryptography.MD5

System.Security.Cryptography.RIPEMD160

System.Security.Cryptography.SHA1

System.Security.Cryptography.SHA256

System.Security.Cryptography.SHA3_256

System.Security.Cryptography.SHA3_384

System.Security.Cryptography.SHA3_512

System.Security.Cryptography.SHA384

System.Security.Cryptography.SHA512

Implements

IDisposable ICryptoTransform

Examples

The following code example computes the SHA256 hash for an array. This example assumes that there is a predefined byte array dataArray[]. SHA256 is a derived class of HashAlgorithm.

HashAlgorithm^ sha = SHA256::Create();
array<Byte>^ result = sha->ComputeHash( dataArray );

HashAlgorithm sha = SHA256.Create();
byte[] result = sha.ComputeHash(dataArray);

Dim sha As SHA256 = SHA256.Create()
Dim result As Byte() = sha.ComputeHash(dataArray)

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.

Due to collision problems with SHA1, Microsoft recommends a security model based on SHA256 or better.

Notes to Implementers

When you inherit from the HashAlgorithm class, you must override the following members: HashCore(Byte[], Int32, Int32) and HashFinal().

Constructors

HashAlgorithm()

Initializes a new instance of the HashAlgorithm class.

Fields

HashSizeValue	Represents the size, in bits, of the computed hash code.
HashValue	Represents the value of the computed hash code.
State	Represents the state of the hash computation.

Properties

CanReuseTransform	Gets a value indicating whether the current transform can be reused.
CanTransformMultipleBlocks	When overridden in a derived class, gets a value indicating whether multiple blocks can be transformed.
Hash	Gets the value of the computed hash code.
HashSize	Gets the size, in bits, of the computed hash code.
InputBlockSize	When overridden in a derived class, gets the input block size.
OutputBlockSize	When overridden in a derived class, gets the output block size.

Methods

Clear()	Releases all resources used by the HashAlgorithm class.
ComputeHash(Byte[], Int32, Int32)	Computes the hash value for the specified region of the specified byte array.
ComputeHash(Byte[])	Computes the hash value for the specified byte array.
ComputeHash(Stream)	Computes the hash value for the specified Stream object.
ComputeHashAsync(Stream, CancellationToken)	Asynchronously computes the hash value for the specified Stream object.
Create()	Obsolete. Creates an instance of the default implementation of a hash algorithm.
Create(String)	Obsolete. Creates an instance of the specified implementation of a hash algorithm.
Dispose()	Releases all resources used by the current instance of the HashAlgorithm class.
Dispose(Boolean)	Releases the unmanaged resources used by the HashAlgorithm and optionally releases the managed resources.
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)	When overridden in a derived class, routes data written to the object into the hash algorithm for computing the hash.
HashCore(ReadOnlySpan<Byte>)	Routes data written to the object into the hash algorithm for computing the hash.
HashFinal()	When overridden in a derived class, finalizes the hash computation after the last data is processed by the cryptographic hash algorithm.
Initialize()	Resets the hash algorithm to its initial state.
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.
TransformFinalBlock(Byte[], Int32, Int32)	Computes the hash value for the specified region of the specified byte array.
TryComputeHash(ReadOnlySpan<Byte>, Span<Byte>, Int32)	Attempts to compute the hash value for the specified byte array.
TryHashFinal(Span<Byte>, Int32)	Attempts to finalize the hash computation after the last data is processed by the hash algorithm.

See also

• Cryptographic Services