xjava.security

Class Mode

Implemented Interfaces:
Parameterized
Known Direct Subclasses:
FeedbackMode

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: 1.3 $

Authors:
David Hopwood
Raif S. Naffah

Since:
IJCE 1.0.1

See Also:
java.security.Cipher

Field Summary

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

Fields inherited from class xjava.security.Cipher

DECRYPT, ENCRYPT, UNINITIALIZED

Fields inherited from class xjava.security.IJCE_Traceable

tracing

Constructor Summary

Mode(boolean implBuffering, boolean implPadding, String provider)
Constructor for a Mode.

Method Summary

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

Methods inherited from class xjava.security.Cipher

blockSize, clone, crypt, crypt, crypt, doFinal, doFinal, doFinal, doFinal, engineBlockSize, engineCiphertextBlockSize, engineCrypt, engineGetParameter, engineInBufferSize, engineInitDecrypt, engineInitEncrypt, engineOutBufferSize, enginePlaintextBlockSize, engineSetPaddingScheme, engineSetParameter, engineUpdate, getAlgorithm, getAlgorithms, getAlgorithms, getCiphertextBlockSize, getInputBlockSize, getInstance, getInstance, getInstance, getMode, getOutputBlockSize, getPadding, getPaddingScheme, getParameter, getPlaintextBlockSize, getProvider, getState, inBufferSize, inBufferSizeFinal, initDecrypt, initEncrypt, isPaddingBlockCipher, outBufferSize, outBufferSizeFinal, setParameter, toString, update, update, update, update

Methods inherited from class xjava.security.IJCE_Traceable

disableTracing, enableTracing, traceMethod, traceResult, traceResult, traceVoidMethod

Field Details

cipher

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

Constructor Details

Mode

protected Mode(boolean implBuffering,
               boolean implPadding,
               String provider)

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.

Method Details

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.

Overrides:
engineGetParameter in interface 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.


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


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.

Overrides:
engineSetParameter in interface 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.
InvalidParameterTypeException - if value is the wrong type for this parameter.


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.
Overrides:
getAlgorithms in interface Cipher


getAlgorithms

public static String[] getAlgorithms(Provider provider)
Gets the standard names of all Modes implemented by a provider.
Overrides:
getAlgorithms in interface Cipher


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.

Overrides:
getInstance in interface Cipher

Parameters:
algorithm - the standard name or an alias for the algorithm.

Returns:
the new Mode object.


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.

Overrides:
getInstance in interface Cipher

Parameters:
algorithm - the standard name or an alias for the algorithm.
provider - the string name of the provider.

Returns:
the new KeyGenerator object.


toString

public String toString()
Overrides:
toString in interface Cipher