Subquantum Crypto Attack

[John Young]

Has subquantum crypto attack been substantiated?

arXiv:quant-ph/0203049v2 12 Apr 2002

Subquantum Information and Computation

Antony Valentini

It is argued that immense physical resources – for nonlocal communication,
espionage, and exponentially-fast computation – are hidden from us by quantum
noise, and that this noise is not fundamental but merely a property of an
equilibrium state in which the universe happens to be at the present time. It
is suggested that ‘non-quantum’ or nonequilibrium matter might exist today in
the form of relic particles from the early 
universe. We describe how such matter
could be detected and put to practical use. Nonequilibrium matter could be
used to send instantaneous signals, to violate 
the uncertainty principle, to distinguish
non-orthogonal quantum states without disturbing them, to eavesdrop
on quantum key distribution, and to outpace quantum computation (solving
NP-complete problems in polynomial time). ...

6 Eavesdropping on Quantum Key Distribution

Alice and Bob want to share a secret sequence of bits that will be used as a
key for cryptography. During distribution of the key between them, they must
be able to detect any eavesdropping by Eve. Three protocols for quantum key
distribution – BB84 [20], B92 [21], and E91 (or EPR) [22] – are known to be
secure against classical or quantum attacks (that 
is, against eavesdropping based
on classical or quantum physics) [23]. But these 
protocols are not secure against
a ‘subquantum’ attack [7]. ...

E91 is particularly interesting for it relies on the completeness of quantum
theory – that is, on the assumption that there 
are no hidden ‘elements of reality’.
Pairs of spin-1/2 particles in the singlet state 
are shared by Alice and Bob, who
perform spin measurements along random axes. For coincident axes the same bit
sequence is generated at each wing, by apparently random quantum outcomes.
‘The eavesdropper cannot elicit any information from the particles while in
transit ..... because there is no information 
encoded there’ [22]. But our Eve has
access to information outside the domain of quantum theory. She can measure
the particle positions while in transit, without 
disturbing the wavefunction, and
so predict the outcomes of spin measurements at the two wings (for the publicly
announced axes).12 Thus Eve is able to predict the key shared by Alice and
Bob.