HMACSHA256 Class

 

Computes a Hash-based Message Authentication Code (HMAC) by using the SHA256 hash function.

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


[<ComVisibleAttribute(true)>]
type HMACSHA256 = 
    class
        inherit HMAC
    end

NameDescription
System_CAPS_pubmethodHMACSHA256()

Initializes a new instance of the HMACSHA256 class with a randomly generated key.

System_CAPS_pubmethodHMACSHA256(Byte[])

Initializes a new instance of the HMACSHA256 class with the specified key data.

NameDescription
System_CAPS_protpropertyBlockSizeValue

Gets or sets the block size to use in the hash value.(Inherited from HMAC.)

System_CAPS_pubpropertyCanReuseTransform

Gets a value indicating whether the current transform can be reused.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyCanTransformMultipleBlocks

When overridden in a derived class, gets a value indicating whether multiple blocks can be transformed.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyHash

Gets the value of the computed hash code.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyHashName

Gets or sets the name of the hash algorithm to use for hashing.(Inherited from HMAC.)

System_CAPS_pubpropertyHashSize

Gets the size, in bits, of the computed hash code.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyInputBlockSize

When overridden in a derived class, gets the input block size.(Inherited from HashAlgorithm.)

System_CAPS_pubpropertyKey

Gets or sets the key to use in the hash algorithm.(Inherited from HMAC.)

System_CAPS_pubpropertyOutputBlockSize

When overridden in a derived class, gets the output block size.(Inherited from HashAlgorithm.)

NameDescription
System_CAPS_pubmethodClear()

Releases all resources used by the HashAlgorithm class.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodComputeHash(Byte[])

Computes the hash value for the specified byte array.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodComputeHash(Byte[], Int32, Int32)

Computes the hash value for the specified region of the specified byte array.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodComputeHash(Stream)

Computes the hash value for the specified Stream object.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodDispose()

Releases all resources used by the current instance of the HashAlgorithm class.(Inherited from HashAlgorithm.)

System_CAPS_protmethodDispose(Boolean)

Releases the unmanaged resources used by the HMAC class when a key change is legitimate and optionally releases the managed resources.(Inherited from HMAC.)

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_protmethodHashCore(Byte[], Int32, Int32)

When overridden in a derived class, routes data written to the object into the default HMAC hash algorithm for computing the hash value.(Inherited from HMAC.)

System_CAPS_protmethodHashFinal()

When overridden in a derived class, finalizes the hash computation after the last data is processed by the cryptographic stream object.(Inherited from HMAC.)

System_CAPS_pubmethodInitialize()

Initializes an instance of the default implementation of HMAC.(Inherited from HMAC.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

System_CAPS_pubmethodTransformBlock(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.(Inherited from HashAlgorithm.)

System_CAPS_pubmethodTransformFinalBlock(Byte[], Int32, Int32)

Computes the hash value for the specified region of the specified byte array.(Inherited from HashAlgorithm.)

NameDescription
System_CAPS_protfieldHashSizeValue

Represents the size, in bits, of the computed hash code.(Inherited from HashAlgorithm.)

System_CAPS_protfieldHashValue

Represents the value of the computed hash code.(Inherited from HashAlgorithm.)

System_CAPS_protfieldKeyValue

The key to use in the hash algorithm.(Inherited from KeyedHashAlgorithm.)

System_CAPS_protfieldState

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

HMACSHA256 is a type of keyed hash algorithm that is constructed from the SHA-256 hash function and used as a Hash-based Message Authentication Code (HMAC). The HMAC process mixes a secret key with the message data, hashes the result with the hash function, mixes that hash value with the secret key again, and then applies the hash function a second time. The output hash is 256 bits in length.

An HMAC can be used to determine whether a message sent over an insecure channel has been tampered with, provided that the sender and receiver share a secret key. The sender computes the hash value for the original data and sends both the original data and hash value as a single message. The receiver recalculates the hash value on the received message and checks that the computed HMAC matches the transmitted HMAC.

Any change to the data or the hash value results in a mismatch, because knowledge of the secret key is required to change the message and reproduce the correct hash value. Therefore, if the original and computed hash values match, the message is authenticated.

HMACSHA256 accepts keys of any size, and produces a hash sequence 256 bits in length.

The following example shows how to sign a file by using the HMACSHA256 object and then how to verify the file.

No code example is currently available or this language may not be supported.

.NET Framework
Available since 2.0
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0

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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