[langsec-discuss] Is computation half the story?

Scott Guthery sbg at acw.com
Fri Mar 27 14:31:52 UTC 2015

>>> The idea here is that if you can combine even the simplest type of 
>>> machine in sufficient quantity, you can do just about anything you like.

Yes, indeed.  But a specific assembly of gates doesn’t do anything or 
everything.  It does a particular thing.  You can make and prove assertions 
about what the assembly does and does not do.  "This assembly of gates 
produces the sum of any two 12-bit integers."  "This assembly of gates will 
loop forever if given an input of 'ABC'."

We don't seek assertions of any possible assembly of gates, only a 
particular assembly --- the one we're going to put in the ATM machine or the 
implanted medical device.

All security is local, to adapt a phrase.

Cheers, Scott

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