On 05/01/2018 20:29, Lawrence D'Oliveiro wrote:
Looks like the repercussions may not be over yet... _______________________________________________ wlug mailing list | wlug(a)list.waikato.ac.nz Unsubscribe: https://list.waikato.ac.nz/mailman/listinfo/wlug
Let me illustrate here one such repercussion: *Computers can lie - same way as humans can* Why? I presume you have read by now that Spectre and Meltdown to succeed rely on speculative execution of commands, a feature introduced into computing to increase overall program execution speed. Speculative execution, in turn, enables side-channel attacks, e.g. a timing attack <https://en.wikipedia.org/wiki/Side-channel_attack>. If you add to this soup what in mathematical logic is known as the Decidability Theorem <https://en.wikipedia.org/wiki/Decidability_%28logic%29>, to quote "Logical systems <https://en.wikipedia.org/wiki/Formal_system> such as propositional logic <https://en.wikipedia.org/wiki/Propositional_calculus> are decidable if membership in their set of logically valid <https://en.wikipedia.org/wiki/Validity> formulas (or theorems) can be effectively determined" you have the facts to construct lies that can be upheld in court (I think so, as I am unable to construct a counter-proof, and I would love to hear what a lawyer has to say). You will find more to the (mathematics) side of what I state here when you google for "decidability theorem". Have a look e.g. at Trakhtenbrot's theorem. The rub is that in order to exclude membership from a set that set has to be finite. If the set is made infinite by allowing recursion, membership can no longer be ascertained, as proven by e.g. Gödel's incompleteness theorems. Now consider this in reverse, and try to construct the set from statements that have been made. That is what a side-channel attack does, re-construct e.g. a password from the time it takes the operating system to dance around the memory location that contains the password. And in the same way a witness can present a lie to court, a journalist to his audience, a politician to her electorate: fail to make a statement that, if made, would have resulted in a different action. Think of George Bush starting the Gulf War, just because his security establishment presumed Saddam Hussein possessed Weapons of Mass Destruction, or, closer to home, think of the Teina Pora case. The defense is always "I didn't (know that, do that, say that)". The human who made the statement did not lie - the lie took effect only because his/her audience interpreted the absence of knowledge as a fact to the contrary, i.e. the audience constructed the set in such a way that it did contain what it actually did not - speculative data processing took place, leading to an interpretation of facts that was decidably false. It became a lie. Such is the link between Mathematical Logic and human behaviour - understand the human mind as a computer capable of speculative processing. Only we call it INITIATIVE, and suppress the ugly word 'speculative'. Wolf