03-07-2012, 03:06 PM
QUANTUM CRYPTOGRAPHY
QUANTUM CRYPTOGRAPHY.pptx (Size: 1.17 MB / Downloads: 32)
This presentation
Quantum mechanics
Introduction
Notation
Polarized photons
Experiment
Quantum cryptology
Key distribution
Eavesdropping
Detecting eavesdropping
Noise
Error correction
Privacy Amplification
Encryption
Cryptography.
Transmitting information with access restricted to the intended recipient even if the message is intercepted by others.
Cryptography is of increasing importance in our technological age using broadcast, network communications, Internet ,e-mail,cell phones which may transmit sensitive information related to finances, politics,business and private confidential matters.
What is Quantum cryptography ?
Quantum
an indivisible elementary particle, usually a photon
+
Cryptography
the practice and study of hiding information
=
Quantum Cryptography
the use of quantum mechanics to guarantee secure communication.
Quantum Key Distribution
BB84 protocol
Charles H. Bennett and Gilles Brassard (1984)
Step 1: Alice sends Bob a string of encoded photons.
Step 2 : Bob measures the string of encoded photons using random bases (rectilinear or diagonal).
Step 3 : Alice and Bob publically compare the bases they encoded and measured in, and discard all results where they do not match.
The result is the Shared Secret Key.
Example
Here is the process Alice and Bob went through to generate their Shared secret key:
Both Alice and Bob have two polarizers each.
One with the 0-90 degree basis (+) and one with 45-135 degree basis (x)
(a) Alice uses her polarizers to send randomly photons to Bob in one of the four possible polarizations 0,45,90,135 degree.
Pros of Public Key Cryptography
High efficiency
Better key distribution and management
No danger that public key is compromised
Certificate authorities
New protocols
Digital signature
State of the QC technology.
Key transmissions can be achieved for about 80 km distance ( Univ of Geneva 2001).
(2)For longer distances we can use repeaters. But practical repeaters are a long way in the future.
Another option is using satellites.
Richard Hughes at LOS ALAMOS NAT LAB (USA) works in this direction.
The satellites distance from earth is in hundreds of kilometers.
Advantages
Nearly Impossible to steal
Detect if someone is listening
“Secure”
Distance Limitations
Availability
vulnerable to DOS
keys can’t keep up with plaintext
What to come
Theory for quantum cryptography already well developed
Problems:
quantum cryptography machine vulnerable to noise
photons cannot travel long distances without being absorbed
Summary
The ability to detect eavesdropping ensures secure exchange of the key
The use of one-time-pads ensures security
Equipment can only be used over short distances
Equipment is complex and expensive
Industrial Prospectsand Tech Transfer
Selling points
Protect secrets long-term/forever $
Distribute large volumes of key efficiently $$
Currently two (count 'em!) commercial implementations of quantum crypto
Potential markets?
Financial services (large key volume)
Government/military (long term secrecy, key dist.)
Ultra-high bandwidth networks, media/content distribution?
Welcome to the Real World
2004 - World's first bank transfer using quantum cryptography in Vienna, Austria.
2004 - DARPA Quantum Cryptographic Network in Massachusetts, USA.
Mar 2007 - BB84 implementation along 148.7 km fibre optic cable in Canary Islands.
Oct 2007 - Quantum Cryptography used in Geneva for Swiss elections.
Oct 2008 - World's first computer network protected by quantum cryptography implemented in Vienna.
Commercial QC providers
id Quantique, Geneva Switzerland
Optical fiber based system
Tens of kilometers distances
MagiQ Technologies, NY City
Optical fiber-glass
Up to 100 kilometers distances
NEC Tokyo 150 kilometers
QinetiQ Farnborough, England
Through the air 10 kilometers.
Supplied system to BBN in Cambridge Mass.