• proth01 Teaser

    From Richard Outerbridge@21:1/5 to All on Sun May 14 08:03:34 2017
    Basic Instructions

    The seed ("key") is any NULL-terminated string of up to 1009 characters.
    1009 is an arbitrary limit; you have to stop somewhere.

    Only letters and numbers count; everything else just counts against.
    Numbers, wherever they appear in the string, are taken literally.

    Letters are all taken for lower case and then enumerated (mod 10) in
    alphabetic order of appearance, skipping the already enumerated.

    From the resulting string of decimal digits are read-off two 18-digit
    numbers and one bit (the IV?), as the state. This is the best I can
    do with a built-in type; the prospect of support for dec128 arithmetic
    would bump this up from 1e18 (2^60) to 1e34 (2^113).

    Of course, using a multi-precision package such as MPD there would be
    no limit to the size of the key (but things would get even slower).

    I think it comes down to whether you can determine what Mod it's
    currently in. That is, can you distinguish (Mx^n %0x0301) %256 from
    the stream (Mx^n %0x1f01) %256? I don't know. I don't even have a
    proof that the generator will always escape the do { } while( 1 ) loop.

    In other words, is it possible to predict the next, or last, bit of
    output without knowing or guessing its Mod as well? Do you also
    need to know or guess the current Mod? So: if you can't distinguish
    either stream from random on its own, how are you going to tell them
    apart when they're put together?


    Even though this software presents itself as a ready-to-use encryption
    solution (albeit a somewhat primitive one) the pseudo-random number
    generator (PRNG) it embodies is NOT held-out to be otherwise in anyway Cryptographically Secure. This software does NOT embody a CSPRNG by
    any means, shape or form. Your Use for whatever purpose is and will
    entirely be at your own risk.

    IN PARTICULAR, the test results reported DO NOT infer an endorsement
    by their respective authors of the use of this software as or for
    the purposes of a Cryptographically Secure Pseudo Random Number
    Generator (CSPRNG). OK?

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