Re: "Small" problem

From: Michael Amling (nospam_at_nospam.com)
Date: 08/16/03

  • Next message: Benjamin Choi: "New stream cipher algorithm, Adaptive Stream Cipher" 
    Date: Sat, 16 Aug 2003 03:32:55 GMT

    Gregory G Rose wrote:
    > [I'm replying to both Alex's and Mike's posts,
    > having never received Mike's.]
    >
    > In article <W7a%a.732212$ro6.15056543@news2.calgary.shaw.ca>,
    > Alex Flanagan <spiffy43@hotmail.com> wrote:
    >
    >>Mike Amling wrote:
    >>>
    >>> You mean if two states for the same date hashed to the same value,
    >>>and the wrong one is found first by the 0..255 loop?
    >
    > Yes, exactly.
    >
    >>> You can avoid this possibility by choosing a k for which it doesn't
    >>>happen. 2**18 messages have to be checked to make sure than no two
    >>>states for a given date produce the same hash. It should take only a few
    >>>seconds on a PC to vet a given k.
    >
    > Not really; that will be true for any given
    > *date*, but you won't be able to choose such a k
    > that will work for arbitrary dates.

       The plan (This not Luby-Rackov. This is the hash plan.) is to send
    the 26 least significant bits of the HMAC_k of (10-bit date concatenated
    with 8-bit state). Dates are allowed to be arbitrary only to the extent
    that they fit into 10 bits. A key can be vetted by comparing all 2**18
    possible different hashes produced for a given k and rejecting k if
    there are any duplicates in the least significant 26 bits. How do you
    arrive at "Not really"?

    --Mike Amling

  • Next message: Benjamin Choi: "New stream cipher algorithm, Adaptive Stream Cipher"

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