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Topic: A software for combining text files to obtain high quality
pseudo-random sequences in practice

Replies: 1   Last Post: Jul 14, 2017 11:43 AM

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Mok-Kong Shen

Posts: 629
Registered: 12/8/04
A software for combining text files to obtain high quality
pseudo-random sequences in practice

Posted: Jul 11, 2017 5:20 AM
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Shannon did some experiments to determine the entropy in English texts.
A later
work done by Cover and King [1] gave an estimate of 1.34 bits per
letter. This
implies that, if the letters are coded into 5 bits, one needs to
appropriately
combine 4 text files in order to obtain bit sequences of full entropy, since
4*1.34 = 5.36 > 5. The method used in our software is to sum (mod 32)
the coded
values of a-z (mapped to 0-25) as 5 bits of the corresponding letters of
the
text files.

There are plenty of other schemes for obtaining high quality pseudo-random
sequences in practice, e.g. AES in counter mode. However our scheme seems to
be much simpler both in the underlying logic (understandability) and in
implementation and is thus a viable alternative that one could use/need
under
circumstances.

The software, TEXTCOMBINE-SP, is available at http://mok-kong-shen.de

M. K. Shen
-------------------------------------------------------------------------------

[1] T. M. Cover, R. C. King, A Convergent Gambling Estimate of the
Entropy of
English, IEEE Trans. Inf. Theory, vol. 24, 1978, pp. 413-421.



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