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Class java.security.Mode

java.lang.Object
   |
   +----java.security.IJCE_Traceable
           |
           +----java.security.Cipher
                   |
                   +----java.security.Mode

public abstract class Mode
extends Cipher
This class is used to provide the functionality of an encryption mode, such as CBC, CFB, or OFB.

Modes are implemented as Ciphers with an additional engine method, engineSetCipher, that is called once to set the underlying cipher algorithm. The Mode class stores this cipher in the protected field cipher. Subclasses are expected to use this to implement their own engineInitEncrypt, engineInitDecrypt and engineUpdate methods.

This class is not supported in JavaSoft's version of JCE.

Copyright © 1997 Systemics Ltd on behalf of the Cryptix Development Team.
All rights reserved.

$Revision: 1.2 $

Author:
David Hopwood, Raif S. Naffah
See Also:
Cipher

Variable Index

 o cipher
A reference to the cipher currently operating in this mode.

Constructor Index

 o Mode(boolean, boolean, String)
Constructor for a Mode.

Method Index

 o engineGetParameter(String)
SPI: Gets the value of the specified algorithm parameter.
 o engineSetCipher(Cipher)
SPI: Sets the underlying cipher.
 o engineSetParameter(String, Object)
SPI: Sets the specified algorithm parameter to the specified value.
 o getAlgorithms()
Gets the standard names of all Modes implemented by any installed provider.
 o getAlgorithms(Provider)
Gets the standard names of all Modes implemented by a provider.
 o getInstance(String)
Generates a Mode object that implements the algorithm requested, as available in the environment.
 o getInstance(String, String)
Generates a Mode object implementing the specified algorithm, as supplied from the specified provider, if such an algorithm is available from the provider.
 o toString()

Variables

 o cipher
 protected Cipher cipher
A reference to the cipher currently operating in this mode.

Constructors

 o Mode
 protected Mode(boolean implBuffering,
                boolean implPadding,
                String provider)
Constructor for a Mode. This constructor is only for use by subclasses, which should pass the correct arguments to convey their behaviour to the superclass. Applications typically do not use Mode classes directly; they should call one of the Cipher.getInstance factory methods instead.

Parameters:
implBuffering - if true, this argument indicates that data will be passed from update/crypt to engineUpdate/engineCrypt without modification.
implPadding - if true, this argument indicates that the implementation can perform padding, and that the engineCrypt method will be called when padding is required.
provider - the name of the provider of the underlying cryptographic engine.
Throws: NullPointerException
if provider == null

Methods

 o getInstance
 public static Cipher getInstance(String algorithm) throws NoSuchAlgorithmException
Generates a Mode object that implements the algorithm requested, as available in the environment.

See International JCE Standard Algorithm Names for a list of Mode algorithm names.

Parameters:
algorithm - the standard name or an alias for the algorithm.
Returns:
the new Mode object.
Throws: NoSuchAlgorithmException
if the algorithm is not available in the environment.
 o getInstance
 public static Cipher getInstance(String algorithm,
                                  String provider) throws NoSuchAlgorithmException, NoSuchProviderException
Generates a Mode object implementing the specified algorithm, as supplied from the specified provider, if such an algorithm is available from the provider.

See International JCE Standard Algorithm Names for a list of Mode algorithm names.

Parameters:
algorithm - the standard name or an alias for the algorithm.
provider - the string name of the provider.
Returns:
the new KeyGenerator object.
Throws: NoSuchAlgorithmException
if the algorithm is not available from the provider.
Throws: NoSuchProviderException
if the provider is not available in the environment.
 o getAlgorithms
 public static String[] getAlgorithms(Provider provider)
Gets the standard names of all Modes implemented by a provider.

 o getAlgorithms
 public static String[] getAlgorithms()
Gets the standard names of all Modes implemented by any installed provider. Algorithm names are not duplicated if they are supported by more than one provider. The built-in mode "ECB" is included.

 o toString
 public String toString()
Overrides:
toString in class Cipher
 o engineSetCipher
 protected void engineSetCipher(Cipher cipher)
SPI: Sets the underlying cipher.

For example, to create an IDEA cipher in CBC mode, the cipher for "IDEA" would be passed to the mode for "CBC" using this method. It is called once, immediately after the mode object is constructed.

Subclasses that override this method (to do initialization that depends on the cipher being set) should call super.engineSetCipher(cipher) first.

Parameters:
cipher - the underlying cipher object
Throws: NullPointerException
if cipher == null
 o engineSetParameter
 protected void engineSetParameter(String param,
                                   Object value) throws NoSuchParameterException, InvalidParameterException, InvalidParameterTypeException
SPI: Sets the specified algorithm parameter to the specified value.

This method supplies a general-purpose mechanism through which it is possible to set the various parameters of this object. The mode implementation should first check whether it recognizes the parameter name, and if not, call super.engineSetParameter(param, value).

A parameter may be any settable parameter for the algorithm, such as block size, a source of random bits for IV generation (if appropriate), or an indication of whether or not to perform a specific but optional computation. A uniform algorithm-specific naming scheme for each parameter is desirable but left unspecified at this time.

The default implementation forwards the call to the underlying cipher.

Parameters:
param - the string name of the parameter.
value - the parameter value.
Throws: NoSuchParameterException
if there is no parameter with name param for this cipher implementation.
Throws: InvalidParameterException
if the parameter exists but cannot be set (for example because the cipher is in the wrong state).
Throws: InvalidParameterTypeException
if value is the wrong type for this parameter.
Overrides:
engineSetParameter in class Cipher
 o engineGetParameter
 protected Object engineGetParameter(String param) throws NoSuchParameterException, InvalidParameterException
SPI: Gets the value of the specified algorithm parameter.

This method supplies a general-purpose mechanism through which it is possible to get the various parameters of this object. The mode implementation should first check whether it recognizes the parameter name, and if not, return super.engineGetParameter(param).

A parameter may be any settable parameter for the algorithm, such as block size, a source of random bits for IV generation (if appropriate), or an indication of whether or not to perform a specific but optional computation. A uniform algorithm-specific naming scheme for each parameter is desirable but left unspecified at this time.

The default implementation forwards the call to the underlying cipher.

Parameters:
param - the string name of the parameter.
Returns:
the object that represents the parameter value.
Throws: NoSuchParameterException
if there is no parameter with name param for this cipher implementation.
Throws: InvalidParameterException
if the parameter exists but cannot be read.
Overrides:
engineGetParameter in class Cipher

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