[Cryptography] combining lots of lousy RNGs ... or not
jsd at av8n.com
Tue Nov 22 23:52:52 EST 2016
On 11/22/2016 08:55 PM, Theodore Ts'o wrote:
> So the question is what do you get if calculate
> H(squish_NSA | squish_KGB | squish_MSS)
> Well, it's certainly not "random", in the formal information
> theoretical sense. But from a _practical_ sense, if you assume that
> the NSA, KGB, and MSS will never collude and/or admit to each other
> that they introduced a NOBUS vulernabiliy into DUAL_EC, RDRAND, and a
> TPM module, it might be _practically_ random.
I disagree. It's an invalid argument leading to an unsound
Among other flaws, the argument depends on the unstated assumption
that a backdoor installed by this-or-that agency cannot possibly
be exploited by anybody else (without the installer's consent).
All evidence indicates that this is not a safe assumption.
-- The Clipper Chip story is widely known.
-- The Snowden documents indicate that many of NSA's favorite
entry points are backdoors installed by *somebody else*.
-- Do you really think that opening the "TSA-Approved" lock on
your suitcase would require "collusion" by a TSA agent?
-- etc. etc. etc.
This is a very serious public-policy issue. Cryptographers (e.g.
Matt Blaze) have been called to testify before Congress. The
point is, when this-or-that agency says something is NOBUS, you
really, really must not assume it is actually NOBUS.
Please do not assume any such thing. It's bad engineering and
bad public policy.
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