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IS THIS TRUE RANDOM ?

Discussion in 'Electronic Design' started by BarNash, Aug 24, 2009.

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  1. BarNash

    BarNash Guest

    Hi all

    I need to implement a true random number generator within a FPGA chip .
    I prefere NOT to rely on an external analog noise source .
    I ask your opnion on the following design idea I have in mind for this .

    The basic idea is to sample a group of 16 bit vectors from a ring
    oscilator and to send out the
    vector that is most far from the last vector sent out before this one .

    The algorythm might look like this :

    1> Sample 10 vectors of 16 bit each from the ring oscilator
    2> send out the most far vector from the last one sent
    3> Sample again 10 vectors of 16 bit each from the ring oscilator
    4> send out the most far vector from the last one sent
    5... so on

    Please express you opinion on this , is this a true random number generator
    ?

    Thanks
    BarNash
     
  2. krw

    krw Guest

    In addition to the good points raised by others here, it's difficult
    to get truly random operation from two seemingly random oscillators.
    They tend to influence each other so don't give the randomness one
    would expect. Testing for randomness is required and non-trivial. To
    give a good distribution of results it's common to pass the outputs of
    the oscillators through an encryption box with a constant key.
     

  3. IDQuantique specialise in quantum encryption using single photons.
    Whilst I wouldn't take their marketing material as gospel, I would assume
    that their products actually work.

    That said, I am happy to use appropriately applied avalanche diodes or
    ring oscillators as entropy sources in my products.


    Disclaimer: I sometimes work for a company that sometimes partners with
    IDQuantique.

    Regards,
    Allan
     
  4. BarNash

    BarNash Guest

    "One CANNOT compute random numbers.
    What is a noisy oscilator ? how do I design one ?
     
  5. krw

    krw Guest

    Certainly not. The encryption box adds no entropy, but "good"
    distributions are usually required to make useful gadgets.
     
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