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gnu.javax.crypto.prng
Class ICMGenerator  view ICMGenerator download ICMGenerator.java

java.lang.Object
  extended bygnu.java.security.prng.BasePRNG
      extended bygnu.javax.crypto.prng.ICMGenerator
All Implemented Interfaces:
java.lang.Cloneable, gnu.java.security.prng.IRandom

public class ICMGenerator
extends gnu.java.security.prng.BasePRNG
implements java.lang.Cloneable

Counter Mode is a way to define a pseudorandom keystream generator using a block cipher. The keystream can be used for additive encryption, key derivation, or any other application requiring pseudorandom data.

In ICM, the keystream is logically broken into segments. Each segment is identified with a segment index, and the segments have equal lengths. This segmentation makes ICM especially appropriate for securing packet-based protocols.

This implementation adheres to the definition of the ICM keystream generation function that allows for any symetric key block cipher algorithm (initialisation parameter gnu.crypto.prng.icm.cipher.name taken to be an instance of java.lang.String) to be used. If such a parameter is not defined/included in the initialisation Map, then the "Rijndael" algorithm is used. Furthermore, if the initialisation parameter gnu.crypto.cipher.block.size (taken to be a instance of java.lang.Integer) is missing or undefined in the initialisation Map, then the cipher's default block size is used.

The practical limits and constraints of such generator are:

NOTE: Rijndael is used as the default symmetric key block cipher algorithm because, with its default block and key sizes, it is the AES. Yet being Rijndael, the algorithm offers more versatile block and key sizes which may prove to be useful for generating longer key streams.

References:

  1. Integer Counter Mode, David A. McGrew.


Field Summary
static java.lang.String BLOCK_INDEX_LENGTH
          Property name of ICM's block index length.
private  java.math.BigInteger blockNdx
          The index of the next block for a given keystream segment.
private  int blockNdxLength
          This keystream block index length in bytes.
private  java.math.BigInteger C0
          The initial counter for a given keystream segment.
private  gnu.javax.crypto.cipher.IBlockCipher cipher
          The underlying cipher implementation.
static java.lang.String CIPHER
          Property name of underlying block cipher for this ICM generator.
static java.lang.String OFFSET
          Property name of ICM's offset.
static java.lang.String SEGMENT_INDEX
          Property name of ICM's segment index.
static java.lang.String SEGMENT_INDEX_LENGTH
          Property name of ICM's segment index length.
private  java.math.BigInteger segmentNdx
          The segment index for this keystream.
private  int segmentNdxLength
          This keystream segment index length in bytes.
private static java.math.BigInteger TWO_FIFTY_SIX
          The integer value 256 as a BigInteger.
 
Fields inherited from class gnu.java.security.prng.BasePRNG
buffer, initialised, name, ndx
 
Constructor Summary
ICMGenerator()
          Trivial 0-arguments constructor.
 
Method Summary
 void fillBlock()
           
 void setup(java.util.Map attributes)
           
 
Methods inherited from class gnu.java.security.prng.BasePRNG
addRandomByte, addRandomBytes, addRandomBytes, clone, init, isInitialised, name, nextByte, nextBytes, nextBytes
 
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

CIPHER

public static final java.lang.String CIPHER
Property name of underlying block cipher for this ICM generator.

See Also:
Constant Field Values

BLOCK_INDEX_LENGTH

public static final java.lang.String BLOCK_INDEX_LENGTH
Property name of ICM's block index length.

See Also:
Constant Field Values

SEGMENT_INDEX_LENGTH

public static final java.lang.String SEGMENT_INDEX_LENGTH
Property name of ICM's segment index length.

See Also:
Constant Field Values

OFFSET

public static final java.lang.String OFFSET
Property name of ICM's offset.

See Also:
Constant Field Values

SEGMENT_INDEX

public static final java.lang.String SEGMENT_INDEX
Property name of ICM's segment index.

See Also:
Constant Field Values

TWO_FIFTY_SIX

private static final java.math.BigInteger TWO_FIFTY_SIX
The integer value 256 as a BigInteger.


cipher

private gnu.javax.crypto.cipher.IBlockCipher cipher
The underlying cipher implementation.


blockNdxLength

private int blockNdxLength
This keystream block index length in bytes.


segmentNdxLength

private int segmentNdxLength
This keystream segment index length in bytes.


blockNdx

private java.math.BigInteger blockNdx
The index of the next block for a given keystream segment.


segmentNdx

private java.math.BigInteger segmentNdx
The segment index for this keystream.


C0

private java.math.BigInteger C0
The initial counter for a given keystream segment.

Constructor Detail

ICMGenerator

public ICMGenerator()
Trivial 0-arguments constructor.

Method Detail

setup

public void setup(java.util.Map attributes)

fillBlock

public void fillBlock()
               throws gnu.java.security.prng.LimitReachedException