An Extended Version of My Encryption Algorithm WEAK3

[Mok-Kong Shen <mok-kong.shen@stud.uni-muenchen.de>]

I have done a trial implementation of a number of suggestions received
for improving my encryption algorithm WEAK3 and have decided to
integrate a subset of these into WEAK3 to form an extended version of
it designated WEAK3-E. The added features are the following:

   1. Text block chaining. Two options are provided. These are similar 
      though not identical to the block chaining methods PBC and CBCC
      as described in B. Schneier's book.

   2. Another block chaining method that is specific to our scheme. It
      consists in modifying, depending on the text being processed, the
      pointers that are used to access the various pseudo-randomly
      generated tables of the algorithm.

   3. All pseudo-randomly generated tables used in the algorithm can now
      be refreshed at user specified periods.

   4. Checksums of the chaining values in (1) and (2) above are output
      to provide integrity checking.

An implementation in Fortran 90 is available in:

     http://www.stud.uni-muenchen.de/~mok-kong.shen/#paper12

The rationales of design of the base version, WEAK3, are given in

     http://www.stud.uni-muenchen.de/~mok-kong.shen/#paper11

The implemented new features largely follow the suggestions of CWL.
I like also to thank GR and CK for construcive critiques and TPS for
validating the program code. All eventual remaining deficiencies and
errors are however exclusively mine.

A binary executable file for PC may be downloaded through:

     http://www.stud.uni-muenchen.de/~mok-kong.shen/#software

Critiques comments and suggestions for improvements are sincerely
solicited.

M. K. Shen