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Class java.security.PaddingScheme

java.lang.Object
   |
   +----java.security.IJCE_Traceable
           |
           +----java.security.PaddingScheme

public abstract class PaddingScheme
extends IJCE_Traceable
implements Parameterized, Padding
This class is extended by classes that provide a general-purpose padding scheme, such as the ones described in PKCS #5 or in RFC 1423 (PEM).

For simplicity, an assumption is made that padding schemes always extend the plaintext to the next block boundary. That is, the input to the padding algorithm always has a length between 0 and blockSize-1, and the output always has length blockSize.

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: 1.7 $

Author:
David Hopwood, Raif S. Naffah

Variable Index

 o blockSize

Constructor Index

 o PaddingScheme(String)
Constructor for a PaddingScheme.

Method Index

 o clone()
Returns a clone of this cipher.
 o engineGetParameter(String)
SPI: Gets the value of the specified algorithm parameter.
 o engineIsValidBlockSize(int)
SPI: Returns true if size is a valid block size (in bytes) for this scheme.
 o enginePad(byte[], int, int)
SPI: Pads a single incomplete block.
 o engineSetBlockSize(int)
Sets the blockSize variable for this instance.
 o engineSetParameter(String, Object)
SPI: Sets the specified algorithm parameter to the specified value.
 o engineUnpad(byte[], int, int)
SPI: Given the specified subarray of bytes that includes padding bytes, returns the index indicating where padding starts.
 o getAlgorithm()
Returns the standard name of the padding scheme implemented.
 o getAlgorithms()
Gets the standard names of all PaddingSchemes implemented by any installed provider.
 o getAlgorithms(Provider)
Gets the standard names of all PaddingSchemes implemented by a provider.
 o getBlockSize()
Returns the block size for this padding scheme.
 o getInstance(String)
Generates a PaddingScheme object that implements the algorithm requested, as available in the environment.
 o getInstance(String, String)
Generates a PaddingScheme object implementing the specified algorithm, as supplied from the specified provider, if such an algorithm is available from the provider.
 o getParameter(String)
Gets the value of the specified algorithm parameter.
 o pad(byte[], int, int)
Pads a given array of bytes.
 o paddingScheme()
Returns the standard name of the padding scheme implemented. Deprecated.
 o padLength(int)
Returns the increase in size that a padding operation would cause on input data of a given length.
 o setParameter(String, Object)
Sets the specified algorithm parameter to the specified value.
 o toString()
 o unpad(byte[], int, int)
Given the specified subarray of bytes that includes padding bytes, returns the index indicating where padding starts.

Variables

 o blockSize
 protected int blockSize

Constructors

 o PaddingScheme
 protected PaddingScheme(String algorithm)
Constructor for a PaddingScheme. This constructor is only for use by subclasses; applications cannot call it directly.

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

Parameters:
algorithm - the standard string name of the algorithm.
Throws: NullPointerException
if algorithm == null

Methods

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

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

Parameters:
algorithm - the standard name or an alias for the algorithm.
Returns:
the new PaddingScheme object.
Throws: NoSuchAlgorithmException
if the algorithm is not available in the environment.
 o getInstance
 public static PaddingScheme getInstance(String algorithm,
                                         String provider) throws NoSuchAlgorithmException, NoSuchProviderException
Generates a PaddingScheme 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 PaddingScheme 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 PaddingSchemes implemented by a provider.

 o getAlgorithms
 public static String[] getAlgorithms()
Gets the standard names of all PaddingSchemes implemented by any installed provider. Algorithm names are not duplicated if they are supported by more than one provider. The built-in PaddingScheme "NONE" is included.

 o getAlgorithm
 public final String getAlgorithm()
Returns the standard name of the padding scheme implemented.

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

Returns:
the standard name of the padding scheme, such as "PKCS#5".
 o getBlockSize
 public final int getBlockSize()
Returns the block size for this padding scheme.

 o pad
 public final int pad(byte in[],
                      int offset,
                      int length)
Pads a given array of bytes. The padding is written to the same buffer that is used for input (in). When this method returns, the padded output will be stored at in[offset .. offset+length+padLength(length)-1].

The in array should be long enough to accomodate the padding.

The return value is the number of bytes written, not the total length of the padded block.

Parameters:
in - the buffer containing the input.
offset - the offset of the bytes to be padded.
length - the number of bytes from the in buffer, starting at offset, that need to be padded.
Returns:
the number of padding bytes written to out.
Throws: ArrayIndexOutOfBoundsException
if offset < 0 || length < 0 || (long)offset + length + padLength(length) > in.length
 o padLength
 public final int padLength(int length)
Returns the increase in size that a padding operation would cause on input data of a given length. This is always blockSize - (length % blockSize).

Parameters:
length - the length of the data to be padded.
Returns:
the increase in size that a padding operation would cause on input of the specified length.
 o unpad
 public final int unpad(byte in[],
                        int offset,
                        int length)
Given the specified subarray of bytes that includes padding bytes, returns the index indicating where padding starts.

length must be at least blockSize.

Parameters:
in - the buffer containing the bytes.
offset - the offset into the in buffer of the first byte in the block.
length - the total length in bytes of the blocks to be unpadded.
Returns:
the index into the in buffer indicating where the padding starts.
Throws: ArrayIndexOutOfBoundsException
if offset < 0 || length < 0 || (long)offset + length > in.length
Throws: IllegalBlockSizeException
if length < blockSize
 o paddingScheme
 public final String paddingScheme()
Note: paddingScheme() is deprecated. Use getAlgorithm() instead.

Returns the standard name of the padding scheme implemented.

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

Returns:
the standard name of the padding scheme.
 o setParameter
 public void setParameter(String param,
                          Object value) throws NoSuchParameterException, InvalidParameterException, InvalidParameterTypeException
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. A uniform algorithm-specific naming scheme for each parameter is desirable but left unspecified at this time.

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

Parameters:
param - the string identifier of the parameter.
value - the parameter value.
Throws: NullPointerException
if param == null
Throws: NoSuchParameterException
if there is no parameter with name param for this padding scheme implementation.
Throws: InvalidParameterException
if the parameter exists but cannot be set.
Throws: InvalidParameterTypeException
if value is the wrong type for this parameter.
 o getParameter
 public Object getParameter(String param) throws NoSuchParameterException, InvalidParameterException
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. A uniform algorithm-specific naming scheme for each parameter is desirable but left unspecified at this time.

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

Parameters:
param - the string name of the parameter.
Returns:
the object that represents the parameter value.
Throws: NullPointerException
if param == null
Throws: NoSuchParameterException
if there is no parameter with name param for this padding scheme implementation.
Throws: InvalidParameterException
if the parameter exists but cannot be read.
 o clone
 public Object clone() throws CloneNotSupportedException
Returns a clone of this cipher.

Throws: CloneNotSupportedException
if the cipher is not cloneable.
Overrides:
clone in class Object
 o toString
 public String toString()
Overrides:
toString in class Object
 o engineSetBlockSize
 protected void engineSetBlockSize(int size)
Sets the blockSize variable for this instance.

Subclasses that override this method (to do initialization that depends on blockSize being set) should call super.engineSetBlockSize(size) first.

Throws: IllegalBlockSizeException
if size < 1 || !engineIsValidBlockSize(size)
 o enginePad
 protected abstract int enginePad(byte in[],
                                  int offset,
                                  int length)
SPI: Pads a single incomplete block.

The padding is written to the same buffer that is used for input (in). When this method returns, the padded block should be stored at in[offset .. offset+blockSize-1].

in will be long enough to accomodate the padding. length is guaranteed to be in the range 0 .. blockSize-1.

Parameters:
in - the buffer containing the incomplete block.
offset - the offset into the in buffer of the block.
length - the number of bytes from the in buffer, starting at offset, that need to be unpadded.
Returns:
the number of padding bytes written.
 o engineUnpad
 protected abstract int engineUnpad(byte in[],
                                    int offset,
                                    int length)
SPI: Given the specified subarray of bytes that includes padding bytes, returns the index indicating where padding starts.

length is guaranteed to be a non-negative multiple of blockSize.

Parameters:
in - the buffer containing the bytes.
offset - the offset into the in buffer of the first byte to be unpadded.
length - the total length in bytes of the blocks to be unpadded.
Returns:
the index into the in buffer indicating where the padding starts.
 o engineIsValidBlockSize
 protected boolean engineIsValidBlockSize(int size)
SPI: Returns true if size is a valid block size (in bytes) for this scheme.

The default implementation always returns true.

 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. A uniform algorithm-specific naming scheme for each parameter is desirable but left unspecified at this time.

The default implementation always throws a NoSuchParameterException.

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

Parameters:
param - the string name of the parameter.
value - the parameter value.
Throws: NoSuchParameterException
if there is no parameter with name param for this padding scheme implementation.
Throws: InvalidParameterException
if the parameter exists but cannot be set.
Throws: InvalidParameterTypeException
if value is the wrong type for this parameter.
 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. A uniform algorithm-specific naming scheme for each parameter is desirable but left unspecified at this time.

The default implementation always throws a NoSuchParameterException.

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

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 padding scheme implementation.
Throws: InvalidParameterException
if the parameter exists but cannot be read.

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