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Re: bike locks and encryption

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On 2014-10-07, RichD <r_delaney2001@yahoo.com> wrote:
> Something occurred to me recntly - bicycle locks 
> as examples of one way functions, so useful in 
> encryption.

What type of bike locks?

All the bicycle locks with which I am familiar are not one-way functions in any
sense. To open the lock, you must show that you either know a secret (the
combination) or that you posess a secret object (the key whose pattern has the
imprint of a combination). The lock itself also contains a representation of
the secret (the configuartion of tumblers, wheels or whatever) in such a way
that this is not externally visible. The secret is not functionally derived
from something else.

Locks do, however, as you suspect, compute a function. Namely, they compute the
boolean function "matches?(lock, key)" or "matches?(lock, combination)": in
other words, they evaluate the predicate whether the secret matches the lock.

Mechanical locks evaluate this function mechanically, powered by the user. For
instance, you rotate some dials to bring them to some configuration, and then
have the lock evaluate the matches? predicate by trying to pull the lock open.
The lock either says "True" by separating or "No" by refusing to separate.

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bike locks and encryption RichD <r_delaney2001@yahoo.com> - 2014-10-06 23:28 -0700
  Re: bike locks and encryption Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-10-07 11:39 +0100
    Re: bike locks and encryption Richard Heathfield <invalid@see.sig.invalid> - 2014-10-07 11:53 +0100
      Re: bike locks and encryption Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-10-07 16:24 +0100
        Re: bike locks and encryption Richard Heathfield <invalid@see.sig.invalid> - 2014-10-07 21:26 +0100
          Re: bike locks and encryption Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-10-08 01:34 +0100
          Re: bike locks and encryption RichD <r_delaney2001@yahoo.com> - 2014-10-07 23:16 -0700
      Re: bike locks and encryption RichD <r_delaney2001@yahoo.com> - 2014-10-07 23:27 -0700
  Re: bike locks and encryption RichD <r_delaney2001@yahoo.com> - 2014-10-07 13:57 -0700
    Re: bike locks and encryption Kaz Kylheku <kaz@kylheku.com> - 2014-10-07 21:21 +0000
      Re: bike locks and encryption "BartC" <bc@freeuk.com> - 2014-10-07 22:33 +0100
        Re: bike locks and encryption Jongware <jongware@no-spam.plz> - 2014-10-08 15:51 +0200
  Re: bike locks and encryption Kaz Kylheku <kaz@kylheku.com> - 2014-10-07 21:10 +0000
    Re: bike locks and encryption RichD <r_delaney2001@yahoo.com> - 2014-10-07 23:34 -0700
      Re: bike locks and encryption Kaz Kylheku <kaz@kylheku.com> - 2014-10-08 14:10 +0000
        Re: bike locks and encryption RichD <r_delaney2001@yahoo.com> - 2014-10-10 18:33 -0700

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