Package javax.crypto

Class ExemptionMechanism

  • public class ExemptionMechanism
extends Object
    This class implements the functionality of an exemption mechanism such as key recovery, key weakening, or key escrow.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      protected void finalize()
      Invoked when the garbage collector has detected that this instance is no longer reachable.
      byte[] genExemptionBlob()
      Generates the result key blob for this exemption mechanism.
      int genExemptionBlob​(byte[] output)
      Generates the result key blob for this exemption mechanism and stores it into the output buffer.
      int genExemptionBlob​(byte[] output, int outputOffset)
      Generates the result key blob for this exemption mechanism and stores it into the output buffer at offset outputOffset.
      static ExemptionMechanism getInstance​(String algorithm)
      Returns a new ExemptionMechanism instance that provides the specified exemption mechanism algorithm.
      static ExemptionMechanism getInstance​(String algorithm, String provider)
      Returns a new ExemptionMechansm instance that provides the specified exemption mechanism algorithm from the specified provider.
      static ExemptionMechanism getInstance​(String algorithm, Provider provider)
      Returns a new ExemptionMechanism instance that provides the specified exemption mechanism algorithm from the specified provider.
      String getName()
      Returns the name of this ExemptionMechanism.
      int getOutputSize​(int inputLen)
      Returns the size in bytes for the output buffer needed to hold the output of the next genExemptionBlob() call, given the specified inputLen (in bytes).
      Provider getProvider()
      Returns the provider of this ExemptionMechanism instance.
      void init​(Key key)
      Initializes this ExemptionMechanism instance with the specified key.
      void init​(Key key, AlgorithmParameters param)
      Initializes this ExemptionMechanism instance with the specified key and algorithm parameters.
      void init​(Key key, AlgorithmParameterSpec param)
      Initializes this ExemptionMechanism instance with the specified key and algorithm parameters.
      boolean isCryptoAllowed​(Key key)
      Returns whether the result blob for this ExemptionMechanism instance has been generated successfully and that the specified key is the same as the one that was used to initialize and generate.

    • Constructor Detail

      • ExemptionMechanism

        protected ExemptionMechanism​(ExemptionMechanismSpi exmechSpi,
                             Provider provider,
                             String mechanism)
        Creates a ExemptionMechanism instance.
        Parameters:
        exmechSpi - the implementation delegate.
        provider - the associated provider.
        mechanism - the name of the mechanism.

    • Method Detail

      • getName

        public final String getName()
        Returns the name of this ExemptionMechanism.
        Returns:
        the name of this ExemptionMechanism.

      • getInstance

        public static final ExemptionMechanism getInstance​(String algorithm)
                                            throws NoSuchAlgorithmException
        Returns a new ExemptionMechanism instance that provides the specified exemption mechanism algorithm.
        Parameters:
        algorithm - the name of the requested exemption mechanism.
        Returns:
        the new ExemptionMechanism instance.
        Throws:
        NoSuchAlgorithmException - if the specified algorithm is not available by any provider.
        NullPointerException - if the algorithm parameter is null.

      • getInstance

        public static final ExemptionMechanism getInstance​(String algorithm,
                                                   Provider provider)
                                            throws NoSuchAlgorithmException
        Returns a new ExemptionMechanism instance that provides the specified exemption mechanism algorithm from the specified provider. The provider supplied does not have to be registered.
        Parameters:
        algorithm - the name of the requested exemption mechanism.
        provider - the provider that is providing the algorithm.
        Returns:
        the new ExemptionMechanism instance.
        Throws:
        NoSuchAlgorithmException - if the specified algorithm is not provided by the specified provider.
        NullPointerException - if the algorithm parameter is null.
        IllegalArgumentException - if the provider parameter is null.

      • getProvider

        public final Provider getProvider()
        Returns the provider of this ExemptionMechanism instance.
        Returns:
        the provider of this ExemptionMechanism instance.

      • isCryptoAllowed

        public final boolean isCryptoAllowed​(Key key)
                              throws ExemptionMechanismException
        Returns whether the result blob for this ExemptionMechanism instance has been generated successfully and that the specified key is the same as the one that was used to initialize and generate.
        Parameters:
        key - the key to verify.
        Returns:
        whether the result blob for this ExemptionMechanism instance has been generated successfully.
        Throws:
        ExemptionMechanismException - if an error occurs while determining whether the result blob has been generated successfully.

      • getOutputSize

        public final int getOutputSize​(int inputLen)
                        throws IllegalStateException
        Returns the size in bytes for the output buffer needed to hold the output of the next genExemptionBlob() call, given the specified inputLen (in bytes).
        Parameters:
        inputLen - the specified input length (in bytes).
        Returns:
        the size in bytes for the output buffer.
        Throws:
        IllegalStateException - if this ExemptionMechanism instance is not initialized.

      • genExemptionBlob

        public final int genExemptionBlob​(byte[] output,
                                  int outputOffset)
                           throws IllegalStateException,
                                  ShortBufferException,
                                  ExemptionMechanismException
        Generates the result key blob for this exemption mechanism and stores it into the output buffer at offset outputOffset.
        Parameters:
        output - the output buffer for the result key blob.
        outputOffset - the offset in the output buffer to start.
        Returns:
        the number of bytes written to the output buffer.
        Throws:
        IllegalStateException - if this ExemptionMechanism instance is not initialized.
        ShortBufferException - if the provided buffer is too small for the result key blob.
        ExemptionMechanismException - if error(s) occur during generation.

      • finalize

        protected void finalize()
        Description copied from class: Object
        Invoked when the garbage collector has detected that this instance is no longer reachable. The default implementation does nothing, but this method can be overridden to free resources.

        Note that objects that override finalize are significantly more expensive than objects that don't. Finalizers may be run a long time after the object is no longer reachable, depending on memory pressure, so it's a bad idea to rely on them for cleanup. Note also that finalizers are run on a single VM-wide finalizer thread, so doing blocking work in a finalizer is a bad idea. A finalizer is usually only necessary for a class that has a native peer and needs to call a native method to destroy that peer. Even then, it's better to provide an explicit close method (and implement Closeable), and insist that callers manually dispose of instances. This works well for something like files, but less well for something like a BigInteger where typical calling code would have to deal with lots of temporaries. Unfortunately, code that creates lots of temporaries is the worst kind of code from the point of view of the single finalizer thread.

        If you must use finalizers, consider at least providing your own ReferenceQueue and having your own thread process that queue.

        Unlike constructors, finalizers are not automatically chained. You are responsible for calling super.finalize() yourself.

        Uncaught exceptions thrown by finalizers are ignored and do not terminate the finalizer thread. See Effective Java Item 7, "Avoid finalizers" for more.

        Overrides:
        finalize in class Object