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package javax.crypto;

import java.security.Key;
import java.security.AlgorithmParameters;
import java.security.InvalidKeyException;
import java.security.InvalidAlgorithmParameterException;
import java.security.spec.AlgorithmParameterSpec;


This class defines the Service Provider Interface (SPI)
for the ExemptionMechanism class.
All the abstract methods in this class must be implemented by each
cryptographic service provider who wishes to supply the implementation
of a particular exemption mechanism.

Author:Sharon Liu
Since:1.4
/**
 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
 * for the <code>ExemptionMechanism</code> class.
 * All the abstract methods in this class must be implemented by each
 * cryptographic service provider who wishes to supply the implementation
 * of a particular exemption mechanism.
 *
 * @author Sharon Liu
 *
 * @since 1.4
 */

public abstract class ExemptionMechanismSpi {

    
Returns the length in bytes that an output buffer would need to be in order to hold the result of the next engineGenExemptionBlob operation, given the input length inputLen (in bytes).

The actual output length of the next engineGenExemptionBlob call may be smaller than the length returned by this method. 
Params:
  • inputLen – the input length (in bytes)
Returns:the required output buffer size (in bytes)
/**
     * Returns the length in bytes that an output buffer would need to be in
     * order to hold the result of the next
     * {@link #engineGenExemptionBlob(byte[], int) engineGenExemptionBlob}
     * operation, given the input length <code>inputLen</code> (in bytes).
     *
     * <p>The actual output length of the next
     * {@link #engineGenExemptionBlob(byte[], int) engineGenExemptionBlob}
     * call may be smaller than the length returned by this method.
     *
     * @param inputLen the input length (in bytes)
     *
     * @return the required output buffer size (in bytes)
     */
    protected abstract int engineGetOutputSize(int inputLen);

    
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.

Params:
  • key – the key for this exemption mechanism
Throws:
/**
     * Initializes this exemption mechanism with a key.
     *
     * <p>If this exemption mechanism requires any algorithm parameters
     * that cannot be derived from the given <code>key</code>, 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
     * <code>InvalidKeyException</code> is raised.
     *
     * @param key the key for this exemption mechanism
     *
     * @exception InvalidKeyException if the given key is inappropriate for
     * this exemption mechanism.
     * @exception ExemptionMechanismException if problem(s) encountered in the
     * process of initializing.
     */
    protected abstract void engineInit(Key key)
    throws InvalidKeyException, 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.

Params:
  • key – the key for this exemption mechanism
  • params – the algorithm parameters
Throws:
/**
     * Initializes this exemption mechanism with a key and a set of algorithm
     * parameters.
     *
     * <p>If this exemption mechanism requires any algorithm parameters and
     * <code>params</code> 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
     * <code>InvalidAlgorithmParameterException</code> is raised.
     *
     * @param key the key for this exemption mechanism
     * @param params the algorithm parameters
     *
     * @exception InvalidKeyException if the given key is inappropriate for
     * this exemption mechanism.
     * @exception InvalidAlgorithmParameterException if the given algorithm
     * parameters are inappropriate for this exemption mechanism.
     * @exception ExemptionMechanismException if problem(s) encountered in the
     * process of initializing.
     */
    protected abstract void engineInit(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.

Params:
  • key – the key for this exemption mechanism
  • params – the algorithm parameters
Throws:
/**
     * Initializes this exemption mechanism with a key and a set of algorithm
     * parameters.
     *
     * <p>If this exemption mechanism requires any algorithm parameters
     * and <code>params</code> 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
     * <code>InvalidAlgorithmParameterException</code> is raised.
     *
     * @param key the key for this exemption mechanism
     * @param params the algorithm parameters
     *
     * @exception InvalidKeyException if the given key is inappropriate for
     * this exemption mechanism.
     * @exception InvalidAlgorithmParameterException if the given algorithm
     * parameters are inappropriate for this exemption mechanism.
     * @exception ExemptionMechanismException if problem(s) encountered in the
     * process of initializing.
     */
    protected abstract void engineInit(Key key, AlgorithmParameters params)
    throws InvalidKeyException, InvalidAlgorithmParameterException,
    ExemptionMechanismException;

    
Generates the exemption mechanism key blob.

Throws:
Returns:the new buffer with the result key blob.
/**
     * Generates the exemption mechanism key blob.
     *
     * @return the new buffer with the result key blob.
     *
     * @exception ExemptionMechanismException if problem(s) encountered in the
     * process of generating.
     */
    protected abstract byte[] engineGenExemptionBlob()
        throws 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 engineGetOutputSize to determine how big the output buffer should be. 
Params:
  • output – the buffer for the result
  • outputOffset – the offset in output where the result
is stored
Throws:
Returns:the number of bytes stored in output
/**
     * Generates the exemption mechanism key blob, and stores the result in
     * the <code>output</code> buffer, starting at <code>outputOffset</code>
     * inclusive.
     *
     * <p>If the <code>output</code> buffer is too small to hold the result,
     * a <code>ShortBufferException</code> is thrown. In this case, repeat this
     * call with a larger output buffer. Use
     * {@link #engineGetOutputSize(int) engineGetOutputSize} to determine
     * how big the output buffer should be.
     *
     * @param output the buffer for the result
     * @param outputOffset the offset in <code>output</code> where the result
     * is stored
     *
     * @return the number of bytes stored in <code>output</code>
     *
     * @exception ShortBufferException if the given output buffer is too small
     * to hold the result.
     * @exception ExemptionMechanismException if problem(s) encountered in the
     * process of generating.
     */
    protected abstract int engineGenExemptionBlob
    (byte[] output, int outputOffset)
        throws ShortBufferException, ExemptionMechanismException;
}