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Class cryptix.provider.rpk.Generator

java.lang.Object
   |
   +----cryptix.util.math.BigRegister
           |
           +----cryptix.util.math.TrinomialLFSR
                   |
                   +----cryptix.provider.rpk.Generator

public class Generator

extends TrinomialLFSR

implements RPKParams, Cloneable, Serializable

When such a generator is clocked, and its state bits matching a specified mask are all zeroes, the next stutter bits are discarded. This effectively provides a non-linear output bit stream.

References:

1. William M. Raike, The RPK Public-Key Cryptographic System - Technical Summary (available at http://crypto.swdev.co.nz).

2. William M. Raike, Detailed Supplemental Technical Description of the RPK Public-Key Cryptographic System (available at http://crypto.swdev.co.nz).

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

$Revision: 1.6 $

Author:

Raif S. Naffah

Generator(int, int)

Instantiate a Generator object using default values for stuttering and stutter mask.

Generator(int, int, int, int)

Instantiate a Generator object given all its characteristics.

clone()

Return a reference to a duplicate of this.

engineClock(int)

Clock this generator with stutter if applicable.

getEncoded()

Return a byte representation of this object.

next(int)

Return the value of the leftmost count bits of this LFSR and clock it by as many ticks.

 public Generator(int l,
                  int k,
                  int m,
                  int s)

Instantiate a Generator object given all its characteristics.

Parameters:

l - Number of stages/delay elements of the LFSR.

k - Value of the mid-tap element completing the trinomial definition.

m - Mask value to govern the frequency of stuttering, ie. non-linearity, of this generator. No checks are done on this value. If it is zero, then this generator will stutter every time it is clocked.

s - Number of bits to discard if the generator's output, at the masked positions, is all zeroes.

Throws: InvalidParameterException

If the (l, k) value pair is not supported by this class.

See Also:

TrinomialLFSR

 public Generator(int l,
                  int k)

Instantiate a Generator object using default values for stuttering and stutter mask.

Parameters:

l - Number of stages/delay elements of the LFSR.

k - Value of the mid-tap element completing the trinomial definition.

See Also:

TrinomialLFSR, DEFAULT_STUTTER_MASK, DEFAULT_STUTTER

 public Object clone()

Return a reference to a duplicate of this.

Overrides:

clone in class TrinomialLFSR

 protected void engineClock(int ticks)

Clock this generator with stutter if applicable.

The bits tested against the mask are the 32 leftmost ones in the FSR.

Parameters:

ticks - number of steps to clock the FSR by. The condition that this value never exceeds the FSR's slice is guaranteed by:

• choosing appropriately the value of stutter at instantiation time, and
• calling the superclass method in 2 steps rather than combining ticks and stutter together.

Overrides:

engineClock in class TrinomialLFSR

 public long next(int count)

Return the value of the leftmost count bits of this LFSR and clock it by as many ticks.

Overrides:

next in class TrinomialLFSR

 public byte[] getEncoded()

Return a byte representation of this object. The semantics of the return byte sequence is as follows:

 Byte    Length
 offset  (bytes)  Meaning
 0       2        The value of the Generator's size, MSB first;
 2       2        The value of the Generator's mid-tap, MSB first;
 4       2        The length of the byte array containing this
                  Generator's register/state, MSB first;
 6       ??       The Generator's register contents.
 

Returns:

An encoding of this object as a byte array or null if an error occured.

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