Re: can we find one-way trapdoor funcation family from the theory of calculus

From: Andrew Swallow (am.swallow_at_btopenworld.com)
Date: 11/21/05

  • Next message: David Wagner: "Re: Provable security of independent encryptions"
    Date: Mon, 21 Nov 2005 20:19:58 +0000 (UTC)
    
    

    Unruh wrote:

    > Andrew Swallow <am.swallow@btopenworld.com> writes:
    >
    >
    >>Unruh wrote:
    >
    >
    >>>Andrew Swallow <am.swallow@btopenworld.com> writes:
    >>>
    >>>
    >>>
    >>>>Unruh wrote:
    >>>>
    >>>>
    >>>>>"Pubkeybreaker" <Robert_silverman@raytheon.com> writes:
    >>>>
    >>>>[snip]
    >>>
    >>>
    >>>>>>Trying to determine, therefore, if it can somehow be made into a
    >>>>>>one-way function
    >>>>>>is just total nonsense.
    >>>>>
    >>>>>
    >>>>>No, but then that was not what they were saying. An integral is a
    >>>>>transformation on a functions. Can such transformations be used to make a
    >>>>>one way function?
    >>>
    >>>
    >>>>You could use something like the sin function. If your number is bigger
    >>>>than 360 then sin(x) cannot be inverted because it is a m:1 function.
    >>>
    >>>
    >>>Unfortunately a trapdoor function is one that can be inverted, just not
    >>>very easily.
    >>>
    >>
    >>Try sin(x + 13N) where N is large
    >>To get from arcsine to x you need to know N.
    >
    >
    > If you know the value for one x (well, actually two x), you know the value for all x. This is a
    > pretty useless trapdoor function. Ie, a single known plaintext/encrypted
    > pair breaks the scheme.
    > Not only do you need unpredictability, you need resistance to known pairs.
    >

    >>In a strong system N would be a function rather than a constant.
    >>Replacement of sin by a binary or integer function would also help.
    >
    >
    >>Andrew Swallow

    That is why N has to be a function.

    Andrew Swallow


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