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A software for combining text files to obtain high quality pseudorandom sequences in practice
Posted:
Jul 11, 2017 5:20 AM


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 az (mapped to 025) as 5 bits of the corresponding letters of the text files.
There are plenty of other schemes for obtaining high quality pseudorandom 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, TEXTCOMBINESP, is available at http://mokkongshen.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. 413421.



