[Cryptography] Questions about crypto that lay people want to understand

John Denker jsd at av8n.com
Tue Dec 22 11:36:00 EST 2015

On 12/21/2015 01:53 PM, Ray Dillinger summarized the contrast
between classical crypto and voting:

> The requirements *are* different, in authentication and
> privacy and in which endpoints are trusted.

The requirements are different yet again for DRM.  In classical
crypto, both endpoints share an interest in keeping the traffic
secret from third parties, but in DRM the endpoints have wildly
different interests.

Like e-voting, some of the goals that you might "want" to achieve
with DRM are simply impossible.


Changing gears:  Another point to be made to the nonspecialists is:

  Metadata is data.
  Stealing metadata is stealing.
  A cryptosystem that leaks metadata is a cryptosystem that leaks.

At the next level of detail:  The whole idea that metadata is somehow
"different" is a legal fiction, arising in the US as a way of getting
around the fourth amendment.  Once upon a time, the kernel of the idea
was:  If you share your data with a third party, it's no longer "your"
data, and it can be seized without a warrant.  This reasoning was applied
to so-called "dialed number recorders".  You lost control at this point,
since you had to give the dialed number to a third party (the telco) to
complete the call.  This was implemented via a "pen register" that was
supposed to be capable of recording the dialed number and nothing else.

IANAL, but despite the foregoing, the plain language of US law, as I
read it, does "generally" require a warrant for pen-register type 

That law makes a certain amount of sense, as a matter of public policy.
It reflects the idea that you "should not" lose all rights to your data
(including metadata!) when it is temporarily entrusted to a third party.

Then a miracle occurred:  legal fiction turned into pharisaical pettifoggery.
By "creative" interpretation of the patriot act, and with the help of
the marsupial FISA court, the NSA decided that they could hoover up
everybody's so-called metadata /without/ a warrant.  In other words, they
gave themselves a "general warrant" which is something the Framers knew
all about.  This is *exactly* what the fourth amendment forbids, and was
intended to forbid.

Furthermore, by additional casuistic chicanery, they gave themselves
a super-expansive definition of "metadata" ... far beyond anything
that was needed for delivery of the message, and far far beyond the
sort of things that could be picked up by a traditional pen register.

This is relevant to crypto because 95% of the world never had fourth
amendment protections to begin with, and in the US none of the three
branches seem interested in upholding the fourth amendment ... so the
only way to obtain even a modicum of privacy is to use encryption.

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