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javax.crypto
Class ExemptionMechanism


java.lang.Object
  extended by javax.crypto.ExemptionMechanism
public class ExemptionMechanism
extends Object

This class provides the functionality of an exemption mechanism, examples of which are key recovery , key weakening , and key escrow .

Applications or applets that use an exemption mechanism may be granted stronger encryption capabilities than those which don't.

Since:
1.4

Constructor Summary
protected ExemptionMechanism ( ExemptionMechanismSpi  exmechSpi, Provider  provider, String  mechanism)
          Creates a ExemptionMechanism object.
 
Method Summary
protected  void finalize ()
          Ensures that the key stored away by this ExemptionMechanism object will be wiped out when there are no more references to it.
 byte[] genExemptionBlob ()
          Generates the exemption mechanism key blob.
 int genExemptionBlob (byte[] output)
          Generates the exemption mechanism key blob, and stores the result in the output buffer.
 int genExemptionBlob (byte[] output, int outputOffset)
          Generates the exemption mechanism key blob, and stores the result in the output buffer, starting at outputOffset inclusive.
static  ExemptionMechanism getInstance ( String
          Generates a ExemptionMechanism object that implements the specified exemption mechanism algorithm. mechanism.
static  ExemptionMechanism getInstance ( String  algorithm,  mechanism, Provider
          Generates a ExemptionMechanism object for the specified exemption mechanism algorithm from the specified provider.
static  ExemptionMechanism getInstance ( String  algorithm,  mechanism, String
          Generates a ExemptionMechanism object for the specified exemption mechanism from the specified provider.
  String getName ()
          Returns the exemption mechanism name of this ExemptionMechanism object.
 int getOutputSize (int inputLen)
          Returns the length in bytes that an output buffer would need to be in order to hold the result of the next genExemptionBlob operation, given the input length inputLen (in bytes).
  Provider getProvider ()
          Returns the provider of this ExemptionMechanism object.
 void init ( Key  key)
          Initializes this exemption mechanism with a key.
 void init ( Key  key, AlgorithmParameters  params)
          Initializes this exemption mechanism with a key and a set of algorithm parameters.
 void init ( Key  key, AlgorithmParameterSpec  params)
          Initializes this exemption mechanism with a key and a set of algorithm parameters.
 boolean isCryptoAllowed ( Key  key)
          Returns whether the result blob has been generated successfully by this exemption mechanism.
 
Methods inherited from class java.lang. Object
clone , equals , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait
 

Constructor Detail

ExemptionMechanism


protected ExemptionMechanism(ExemptionMechanismSpi exmechSpi,
                             Provider provider,
                             String mechanism)
Creates a ExemptionMechanism object.

Parameters:
exmechSpi - the delegate
provider - the provider
mechanism - the exemption mechanism
Method Detail

getName


public final String getName()
Returns the exemption mechanism name of this ExemptionMechanism object.

This is the same name that was specified in one of the getInstance calls that created this ExemptionMechanism object.

Returns:
the exemption mechanism name of this ExemptionMechanism object.

getInstance


public static final ExemptionMechanismgetInstance(String algorithm)
  mechanism)
 throws NoSuchAlgorithmException
Generates a ExemptionMechanism object that implements the specified exemption mechanism algorithm. mechanism. If the default provider package provides an implementation of the requested exemption mechanism algorithm, mechanism, an instance of ExemptionMechanism containing that implementation is returned. If the exemption mechanism is not available in the default provider package, other provider packages are searched.

Parameters:
algorithm mechanism - the standard name of the requested exemption mechanism. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard exemption mechanism names.
Returns:
the new ExemptionMechanism object
Throws:
NullPointerException - if algorithm is null.
NoSuchAlgorithmException - if the specified algorithm exemption mechanism is not available in the default provider package or any of the other provider packages that were searched.

getInstance


public static final ExemptionMechanismgetInstance(String algorithm,
  mechanism,
 String provider)
                                            throws NoSuchAlgorithmException,
                                                   NoSuchProviderException
Generates a ExemptionMechanism object for the specified exemption mechanism from the specified provider.

Parameters:
algorithm mechanism - the standard name of the requested exemption mechanism. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard exemption mechanism names.
provider - the name of the provider
Returns:
the new ExemptionMechanism object
Throws:
NullPointerException - if algorithm is null.
NoSuchAlgorithmException - if the specified algorithm exemption mechanism is not available from the specified provider.
NoSuchProviderException - if the specified provider has not been configured.
IllegalArgumentException - if the provider is null.

getInstance


public static final ExemptionMechanismgetInstance(String algorithm,
  mechanism,
 Provider provider)
                                            throws NoSuchAlgorithmException
Generates a ExemptionMechanism object for the specified exemption mechanism algorithm from the specified provider. Note: the provider doesn't have to be registered.

Parameters:
algorithm mechanism - the standard name of the requested exemption mechanism. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard exemption mechanism names.
provider - the provider
Returns:
the new ExemptionMechanism object
Throws:
NullPointerException - if algorithm is null.
NoSuchAlgorithmException - if the specified algorithm exemption mechanism is not available from the specified provider.
IllegalArgumentException - if the provider is null.

getProvider


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

Returns:
the provider of this ExemptionMechanism object.

isCryptoAllowed


public final boolean isCryptoAllowed(Key key)
                              throws ExemptionMechanismException
Returns whether the result blob has been generated successfully by this exemption mechanism.

The method also makes sure that the key passed in is the same as the one this exemption mechanism used in initializing and generating phases.

Parameters:
key - the key the crypto is going to use.
Returns:
whether the result blob of the same key has been generated successfully by this exemption mechanism; false if key is null. mechanism.
Throws:
ExemptionMechanismException - if problem(s) encountered while determining whether the result blob has been generated successfully by this exemption mechanism object.

getOutputSize


public final int getOutputSize(int inputLen)
                        throws IllegalStateException
Returns the length in bytes that an output buffer would need to be in order to hold the result of the next genExemptionBlob operation, given the input length inputLen (in bytes).

The actual output length of the next genExemptionBlob call may be smaller than the length returned by this method.

Parameters:
inputLen - the input length (in bytes)
Returns:
the required output buffer size (in bytes)
Throws:
IllegalStateException - if this exemption mechanism is in a wrong state (e.g., has not yet been initialized)

init


public final void init(Key key)
                throws InvalidKeyException,
                       ExemptionMechanismException
Initializes this exemption mechanism with a key.

If this exemption mechanism requires any algorithm parameters that cannot be derived from the given key, the underlying exemption mechanism implementation is supposed to generate the required parameters itself (using provider-specific default values); in the case that algorithm parameters must be specified by the caller, an InvalidKeyException is raised.

Parameters:
key - the key for this exemption mechanism
Throws:
InvalidKeyException - if the given key is inappropriate for this exemption mechanism.
ExemptionMechanismException - if problem(s) encountered in the process of initializing.

init


public final void init(Key key,
                       AlgorithmParameterSpec params)
                throws InvalidKeyException,
                       InvalidAlgorithmParameterException,
                       ExemptionMechanismException
Initializes this exemption mechanism with a key and a set of algorithm parameters.

If this exemption mechanism requires any algorithm parameters and params is null, the underlying exemption mechanism implementation is supposed to generate the required parameters itself (using provider-specific default values); in the case that algorithm parameters must be specified by the caller, an InvalidAlgorithmParameterException is raised.

Parameters:
key - the key for this exemption mechanism
params - the algorithm parameters
Throws:
InvalidKeyException - if the given key is inappropriate for this exemption mechanism.
InvalidAlgorithmParameterException - if the given algorithm parameters are inappropriate for this exemption mechanism.
ExemptionMechanismException - if problem(s) encountered in the process of initializing.

init


public final void init(Key key,
                       AlgorithmParameters params)
                throws InvalidKeyException,
                       InvalidAlgorithmParameterException,
                       ExemptionMechanismException
Initializes this exemption mechanism with a key and a set of algorithm parameters.

If this exemption mechanism requires any algorithm parameters and params is null, the underlying exemption mechanism implementation is supposed to generate the required parameters itself (using provider-specific default values); in the case that algorithm parameters must be specified by the caller, an InvalidAlgorithmParameterException is raised.

Parameters:
key - the key for this exemption mechanism
params - the algorithm parameters
Throws:
InvalidKeyException - if the given key is inappropriate for this exemption mechanism.
InvalidAlgorithmParameterException - if the given algorithm parameters are inappropriate for this exemption mechanism.
ExemptionMechanismException - if problem(s) encountered in the process of initializing.

genExemptionBlob


public final byte[] genExemptionBlob()
                              throws IllegalStateException,
                                     ExemptionMechanismException
Generates the exemption mechanism key blob.

Returns:
the new buffer with the result key blob.
Throws:
IllegalStateException - if this exemption mechanism is in a wrong state (e.g., has not been initialized).
ExemptionMechanismException - if problem(s) encountered in the process of generating.

genExemptionBlob


public final int genExemptionBlob(byte[] output)
                           throws IllegalStateException,
                                  ShortBufferException,
                                  ExemptionMechanismException
Generates the exemption mechanism key blob, and stores the result in the output buffer.

If the output buffer is too small to hold the result, a ShortBufferException is thrown. In this case, repeat this call with a larger output buffer. Use getOutputSize to determine how big the output buffer should be.

Parameters:
output - the buffer for the result
Returns:
the number of bytes stored in output
Throws:
IllegalStateException - if this exemption mechanism is in a wrong state (e.g., has not been initialized).
ShortBufferException - if the given output buffer is too small to hold the result.
ExemptionMechanismException - if problem(s) encountered in the process of generating.

genExemptionBlob


public final int genExemptionBlob(byte[] output,
                                  int outputOffset)
                           throws IllegalStateException,
                                  ShortBufferException,
                                  ExemptionMechanismException
Generates the exemption mechanism key blob, and stores the result in the output buffer, starting at outputOffset inclusive.

If the output buffer is too small to hold the result, a ShortBufferException is thrown. In this case, repeat this call with a larger output buffer. Use getOutputSize to determine how big the output buffer should be.

Parameters:
output - the buffer for the result
outputOffset - the offset in output where the result is stored
Returns:
the number of bytes stored in output
Throws:
IllegalStateException - if this exemption mechanism is in a wrong state (e.g., has not been initialized).
ShortBufferException - if the given output buffer is too small to hold the result.
ExemptionMechanismException - if problem(s) encountered in the process of generating.

finalize


protected void finalize()
Ensures that the key stored away by this ExemptionMechanism object will be wiped out when there are no more references to it.

Overrides:
finalize in class Object