Class KEM.Decapsulator

java.lang.Object

javax.crypto.KEM.Decapsulator

Enclosing class:

KEM

public static final class KEM.Decapsulator
extends Object

A decapsulator, generated by KEM.newDecapsulator(PrivateKey) on the KEM receiver side.

This class represents the key decapsulation function of a KEM. An invocation of the decapsulate method recovers the secret key from the key encapsulation message.

Since:

21

Method Summary

Modifier and Type	Method	Description
SecretKey	decapsulate(byte[] encapsulation)	The key decapsulation function.
SecretKey	decapsulate(byte[] encapsulation, int from, int to, String algorithm)	The key decapsulation function.
int	encapsulationSize()	Returns the size of the key encapsulation message.
String	providerName()	Returns the name of the provider.
int	secretSize()	Returns the size of the shared secret.

Methods declared in class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Modifier and Type	Method	Description
protected Object	clone()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Method Details

providerName

public String providerName()

Returns the name of the provider.

Returns:

the name of the provider

decapsulate

public SecretKey decapsulate(byte[] encapsulation)
                      throws DecapsulateException

The key decapsulation function.

This method is equivalent to decapsulate(encapsulation, 0, secretSize(), "Generic"). This combination of arguments must be supported by every implementation.

The generated secret key is usually passed to a key derivation function (KDF) as the input keying material.

Parameters:

encapsulation - the key encapsulation message from the sender. The size must be equal to the value returned by encapsulationSize(), or a DecapsulateException will be thrown.

Returns:

the shared secret as a SecretKey with an algorithm name of "Generic"

Throws:

DecapsulateException - if an error occurs during the decapsulation process

NullPointerException - if encapsulation is null

decapsulate

public SecretKey decapsulate(byte[] encapsulation,
 int from,
 int to,
 String algorithm)
                      throws DecapsulateException

The key decapsulation function.

An invocation of this method recovers the secret key from the key encapsulation message.

An implementation may choose to not support arbitrary combinations of from, to, and algorithm.

Parameters:

encapsulation - the key encapsulation message from the sender. The size must be equal to the value returned by encapsulationSize(), or a DecapsulateException will be thrown.

from - the initial index of the shared secret byte array to be returned, inclusive

to - the final index of the shared secret byte array to be returned, exclusive

algorithm - the algorithm name for the secret key that is returned. See the SecretKey Algorithms section in the Java Security Standard Algorithm Names Specification for information about standard secret key algorithm names. Specify "Generic" if the output will be used as the input keying material of a key derivation function (KDF).

Returns:

a portion of the shared secret as a SecretKey containing the bytes of the secret ranging from from to to, exclusive, and an algorithm name as specified. For example, decapsulate(encapsulation, secretSize() - 16, secretSize(), "AES") uses the last 16 bytes of the shared secret as a 128-bit AES key.

Throws:

DecapsulateException - if an error occurs during the decapsulation process

IndexOutOfBoundsException - if from < 0, from > to, or to > secretSize()

NullPointerException - if encapsulation or algorithm is null

UnsupportedOperationException - if the combination of from, to, and algorithm is not supported by the decapsulator

External Specifications

• Java Security Standard Algorithm Names

secretSize

public int secretSize()

Returns the size of the shared secret.

This method can be called to find out the length of the shared secret before decapsulate is called or if the obtained SecretKey is not extractable.

Returns:

the size of the shared secret

encapsulationSize

public int encapsulationSize()

Returns the size of the key encapsulation message.

This method can be used to extract the encapsulation message from a longer byte array if no length information is provided by a higher level protocol.

Returns:

the size of the key encapsulation message