Post by Sylvia Else Post by Computer Nerd Kev Post by Sylvia Else
Any communications channel should be treated as not being trusted, and
that certainly applies to things like Wifi. If that philosophy is
followed, then the worst that should be possible by hacking it is a
denial of service. In the context of traffic lights, that should only
mean that the phasing cannot be changed by a manned control centre in
response to traffic conditions.
What if hackers were spoofing commands which the traffic lights think
are coming from the control centre (assuming that they have found a
vulnerability in whatever system should be used to authenticate such
commands)? They could configure them to cause maximum disruption even
if they can't stop them working altogether.
Authentication of cryptographically signed commands is, at its core,
very simple. The complexity in the system used for things like TLS
derives from the need to allow multiple algorithms, and the use of
session keys. None of that is necessary for authentication traffic light
commands, and there should be no difficulty implementing such a system
with no vulnerabilities [*].
If the hackers were able to obtain the signing key, then they could get
more control over the system, but still only to the extent of changing
the phasing within preset limits, where those limits themselves depend
on the time of day.
I see what you're getting at, but there are opposing goals in that
approach where it takes away from the degree of flexibility that the
system was designed to implement in the first place. For example what
about when road works or traffic accidents cause traffic to be
rerouted, does it have to be needlessly held up at lights which are
forced to preference flow through the usual traffic routes?
Post by Sylvia Else
[*] As long as the factorisation problem remains unsolved.
I took this as an excuse to look far too deeply into the current
state of attacks on encryption:
I think the current bet is on quantum computers simply becoming
powerful enough to adequately implement one of the solutions that
It's still a long way from the being useful, but going from being
able to factorise 143 in 2012 to having one realise that 659 571s
make 376,289 last year seems a decent rate of advancement to my
uneducated eye. Of course the key thing is that these computers find
the answer in only a few seconds.
-Granted the author of that Stack Exchange answer has a different
This paper estimates the minimum specs for a quantum computer able
to break the factorisation problem for RSA, and also the alternative
Eliptic curve method (which turns out to be easier for quantum
computers to beat):
-Page 21 for results summarised in table 2.
That caims that a quantum computer with at least a few thousand
qbits would be required to effictively attack currently used
encryption systems. The current top-end seems to be 72qb. Though
the metric of qbits is complicated in the case of the "Quantum
annealing" D-Wave computer that found the factors of 376,289,
because this actually has 2048qb. However it works in a different
way (more akin in principle to an old fashioned analogue computer,
but using "quantum magnetism" instead of analogue electrical
signals - at least that's how I'm reading it) compared to "universal"
quantum computers from other manufacturers, and the relationship of
qbits to computing power isn't (at least directly) comparable between
them. Nevertheless in this task it seems that quantum annealing
currently has the edge.
IARPA, the equivalent of DARPA for the American intelligence
agencies, is very involved in the development of quantum
computing research, probably in combination with manufacturers of
commercial quantum computers. So it seems likely that the true state
of the art might be at least one step ahead of what's public.
Maybe to say that a universal quantum computer with thousands of
qbits is currently impossible today is akin to a German saying that
a computer built from 1,600 valves was impossible in 1944, while
Colossus was whirring away decrypting all of their war plans.
In any case, quantum computers are already being bought by companies
looking to use them for improved methods of encryption:
And this new chip designed for "post-quantum encryption" might even
be suited for use in a traffic light controller if it were on the
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