Module java.base
Package javax.crypto

Class KEM.Encapsulator

java.lang.Object
javax.crypto.KEM.Encapsulator
Enclosing class:
KEM
public static final class KEM.Encapsulator extends Object
An encapsulator, generated by KEM.newEncapsulator(java.security.PublicKey) on the KEM sender side.

This class represents the key encapsulation function of a KEM. Each invocation of the encapsulate method generates a new secret key and key encapsulation message that is returned in an KEM.Encapsulated object.

API Note:
This class is defined in Java SE 17 Maintenance Release 1.
Since:
17

  • Method Details

    • providerName

      public String providerName()
      Returns the name of the provider.
      Returns:
      the name of the provider

    • encapsulate

      public KEM.Encapsulated encapsulate()
      The key encapsulation function.

      This method is equivalent to encapsulate(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.

      Returns:
      a KEM.Encapsulated object containing the shared secret, key encapsulation message, and optional parameters. The shared secret is a SecretKey containing all of the bytes of the secret, and an algorithm name of "Generic".

    • encapsulate

      public KEM.Encapsulated encapsulate(int from, int to, String algorithm)
      The key encapsulation function.

      Each invocation of this method generates a new secret key and key encapsulation message that is returned in an KEM.Encapsulated object.

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

      Parameters:
      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
      Returns:
      a KEM.Encapsulated object containing a portion of the shared secret, key encapsulation message, and optional parameters. The portion of the shared secret is a SecretKey containing the bytes of the secret ranging from from to to, exclusive, and an algorithm name as specified. For example, encapsulate(0, 16, "AES") uses the first 16 bytes of the shared secret as a 128-bit AES key.
      Throws:
      IndexOutOfBoundsException - if from < 0, from > to, or to > secretSize()
      NullPointerException - if algorithm is null
      UnsupportedOperationException - if the combination of from, to, and algorithm is not supported by the encapsulator

    • 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 encapsulate 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 called to find out the length of the encapsulation message before encapsulate is called.

      Returns:
      the size of the key encapsulation message