09/05/2008, 15:00 — 16:00 — Room P3.10, Mathematics Building
Geraldo A. Barbosa, Center for Photonic Communication and Computing, Northwestern University, USA
Platform for telecommunications secured by physical noise
Classical: Protection existing in classical cryptographic
systems widely used is based on keys generated by pseudo-random
number generators or computational complexities (e.g., factoring
large numbers into primes). However, pseudo-random sequences have
formation rules and algorithms can be used or discovered to find
the sequences. Also, other than historical difficulties nothing
indicates that an efficient (classical) factoring algorithm cannot
be found.
“One-time pad” encryption is the only classical method
offering unconditional security. It uses secret symmetric keys [G.
S. Vernam, J. Amer. Inst. Elec. Eng. 55, 109 (1926). C. E. Shannon,
Bell Syst. Tech. J. 28, 656 (1949)] shared between two users. The
difficulty to securely renew the shared keys in modern fast
communications is an unsolved challenge that ruled out this
technique for broad use.
Quantum: Quantum protocols, such as the well studied
single-photon protocol BB84 offer outstanding protection in
dedicated networks for short distances and at slow speeds . These
systems do not work in generic Internet channels and networks. Good
signal amplification is not possible with single photon protocols
[Wootters-Zurek theorem: Wooters WK, Zurek WH, Nature, 299 (5886)
1982, 802-803] and the system security reduces to zero if signals
are converted from optical to electrical and vice-versa; these
conversions are necessary in generic Internet channels. Although
systems using continuous variables and other schemes are constantly
being proposed, there is no widely accepted vision on purely
quantum systems being incorporated to the
Internet.
Systems
protected by physical noise: A new class of systems was
recently created based on physical noise that, even not offering
unconditional security, offer security levels compatible or higher
than current protocols. They do not rely on the factoring
difficulty and do not need certificate centers; they are under
strict control of the users, sender and receiver. They mix
classical protocols and quantum noise features. They do not use
single photons in entangled states. These systems were created to
offer high level of security and at the same time work at high
speeds compatible to modern communications. It is practical to have
them classified in data encryption systems and key
distribution systems.
The
data encryption systems are known as alpha eta systems (and
as Y00 in Japan) and were created at Northwestern University
through a DARPA supported project that led to Patent No. US
7,333,611 (Feb. 19, 2008) [Assignee: Northwestern University,
Inventors: H. P. Yuen, P. Kumar, and G. A. Barbosa]. They were
created to operate in fiber channels and use the intrinsic light
noise associate to the signal carrier to blur the signal to the
attacker while giving the legitimate users a clear signal (see
patent). They operate at the physical layer of the communication
networks. This kind of system has already been tested in the United
States (experimental networks in Washington and currently in the
DARPA Quantum Network in Boston) and Japan. It is already
being developed by a new company called NuCrypt, directed by one of
the inventors (P. Kumar).
The
key distribution system (patented by US-2005-0152540-A1,
Inventor: G. A. Barbosa) is the main object of this talk. This
system has two versions, one for fiber channels and another one to
operate on the user layer. Both start with a sequence of truly
random keys shared by the legitimate users. These keys are
generated by a Physical Random Generator (PhRG). There is no
intrinsic physical limitation for the key generation process speed.
This speed may evolve according to the electronic technology
advances and may follow computation and the web’s speed
evolution. This is in contrast with single-photon cryptographic
methods that are inherently slow.
This
starting shared sequence provides the security core onto which an
attacker has to brake in to obtain the fresh key sequences being
constantly generated by the same PhRG and constantly shared by the
users. This difficulty is easily set at a computational difficulty
level well above current capabilities and is also easily adapted to
any computational advances. The sequences of fresh keys shared by
the users are used for fast bit-by-bit or block
encryption.
Security measures have yet to be developed as well as a working
prototype.
Join us
in this effort.
Some
references:
Optical
fiber channel:
- Fast and secure key
distribution using mesoscopic coherent states of light; GA Barbosa,
Phys. Rev. A 68, 052307 (2003).
- Information theory for
key distribution systems secured by mesoscopic coherent states; G.
A. Barbosa, Phys. Rev. A 71, 062333 (2005).
Generic
Internet channel:
- Noise Secured Internet;
G. A. Barbosa, quant/ph0510011 (2005).
- Fundamentals for
immediate implementation of a quantum secured Internet; G. A.
Barbosa, quant-ph/0607093 v2 16 Aug 2006.
- Secure sharing of random
bits over the Internet; G. A. Barbosa, quant-ph/0705.2243 v2 17 17
May 07.
