Class ExemptionMechanism
- java.lang.Object
-
- 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
Modifier | Constructor | Description |
---|---|---|
protected | ExemptionMechanism(ExemptionMechanismSpi exmechSpi,
Provider provider,
String mechanism) | Creates a ExemptionMechanism object. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
byte[] | genExemptionBlob() | Generates the exemption mechanism key blob. |
int | genExemptionBlob(byte[] output) | Generates the exemption mechanism key blob, and stores the result in the |
int | genExemptionBlob(byte[] output,
int outputOffset) | Generates the exemption mechanism key blob, and stores the result in the |
static ExemptionMechanism | getInstance(String algorithm) | Returns an |
static ExemptionMechanism | getInstance(String algorithm,
String provider) | Returns an |
static ExemptionMechanism | getInstance(String algorithm,
Provider provider) | Returns an |
String | getName() | Returns the exemption mechanism name of this |
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 |
Provider | getProvider() | Returns the provider of this |
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 declared in class java.lang.Object
clone, equals, finalize, 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 ExemptionMechanism getInstance(String algorithm) throws NoSuchAlgorithmException
Returns an ExemptionMechanism
object that implements the specified exemption mechanism algorithm.
This method traverses the list of registered security Providers, starting with the most preferred Provider. A new ExemptionMechanism object encapsulating the ExemptionMechanismSpi implementation from the first Provider that supports the specified algorithm is returned.
Note that the list of registered providers may be retrieved via the Security.getProviders()
method.
- Implementation Note:
- The JDK Reference Implementation additionally uses the
jdk.security.provider.preferred
Security
property to determine the preferred provider order for the specified algorithm. This may be different than the order of providers returned bySecurity.getProviders()
. - Parameters:
-
algorithm
- the standard name of the requested exemption mechanism. See the ExemptionMechanism section in the Java Security Standard Algorithm Names Specification for information about standard exemption mechanism names. - Returns:
- the new
ExemptionMechanism
object - Throws:
-
NoSuchAlgorithmException
- if noProvider
supports anExemptionMechanismSpi
implementation for the specified algorithm -
NullPointerException
- ifalgorithm
isnull
- See Also:
Provider
getInstance
public static final ExemptionMechanism getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException
Returns an ExemptionMechanism
object that implements the specified exemption mechanism algorithm.
A new ExemptionMechanism object encapsulating the ExemptionMechanismSpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.
Note that the list of registered providers may be retrieved via the Security.getProviders()
method.
- Parameters:
-
algorithm
- the standard name of the requested exemption mechanism. See the ExemptionMechanism section in the Java Security Standard Algorithm Names Specification for information about standard exemption mechanism names. -
provider
- the name of the provider. - Returns:
- the new
ExemptionMechanism
object - Throws:
-
IllegalArgumentException
- if theprovider
isnull
or empty -
NoSuchAlgorithmException
- if anExemptionMechanismSpi
implementation for the specified algorithm is not available from the specified provider -
NoSuchProviderException
- if the specified provider is not registered in the security provider list -
NullPointerException
- ifalgorithm
isnull
- See Also:
Provider
getInstance
public static final ExemptionMechanism getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException
Returns an ExemptionMechanism
object that implements the specified exemption mechanism algorithm.
A new ExemptionMechanism object encapsulating the ExemptionMechanismSpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.
- Parameters:
-
algorithm
- the standard name of the requested exemption mechanism. See the ExemptionMechanism section in the Java Security Standard Algorithm Names Specification for information about standard exemption mechanism names. -
provider
- the provider. - Returns:
- the new
ExemptionMechanism
object - Throws:
-
IllegalArgumentException
- if theprovider
is null -
NoSuchAlgorithmException
- if anExemptionMechanismSpi
implementation for the specified algorithm is not available from the specifiedProvider object
-
NullPointerException
- ifalgorithm
isnull
- See Also:
Provider
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. - 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 inoutput
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.