Quantum EncryptionQuantum Encryption

Cryptography’s Holy GrailCryptography’s Holy Grail

by Samantha Matthewsby Samantha Matthews

Conventional EncryptionConventional Encryption

Data transmission is asynchronous.Data transmission is asynchronous. Data are sent in groups of photons and Data are sent in groups of photons and

translated by the receiving computer.translated by the receiving computer. The encryption key is sent embedded in The encryption key is sent embedded in

the data stream and can be intercepted in the data stream and can be intercepted in transit without either party’s knowledge.transit without either party’s knowledge.

Quantum EncryptionQuantum Encryption

Data transmission is synchronous.Data transmission is synchronous. Data are sent in weak pulses of photons.Data are sent in weak pulses of photons. The physical behavior of the particles The physical behavior of the particles

themselves gives the receiver the encryption themselves gives the receiver the encryption key.key.

If a third party interrupts the data stream, the If a third party interrupts the data stream, the encryption key is rendered useless and both encryption key is rendered useless and both parties are alerted.parties are alerted.

The encryption key isn’t The encryption key isn’t inin the message, it the message, it isis the message.the message.

Why Quantum Encryption WorksWhy Quantum Encryption Works

Subatomic particles can exist in multiple Subatomic particles can exist in multiple states until something interacts with them and states until something interacts with them and changes those states.changes those states.

Heisenberg’s Uncertainty PrincipleHeisenberg’s Uncertainty Principle ppxx1/2*h/21/2*h/2 We can know the location or linear We can know the location or linear

momentum of a particle, but not both.momentum of a particle, but not both. Think of Schrödinger's cat, a quantum Think of Schrödinger's cat, a quantum

mechanical outgrowth of this principle.mechanical outgrowth of this principle.

Why Quantum Encryption Works, Why Quantum Encryption Works, Part 2Part 2

It makes use of quantum entanglement, It makes use of quantum entanglement, the interdependency of the physical the interdependency of the physical states of quantum particles.states of quantum particles.

Changing the state of one particle Changing the state of one particle (through observation) changes the state (through observation) changes the state of other particles around it.of other particles around it.

How Quantum Encryption Works How Quantum Encryption Works on the Sender’s Endon the Sender’s End

A laser separates individual photons and sends them A laser separates individual photons and sends them to an instrument called a modulator.to an instrument called a modulator.

The modulator sends the photons to other network The modulator sends the photons to other network nodes via fiber-optic cable.nodes via fiber-optic cable.

The photons are encoded by sending them at different The photons are encoded by sending them at different time intervals.time intervals.

Chip Elliot, an engineer for BBN Technologies, next to a quantum cryptograph.

How Quantum Encryption Works How Quantum Encryption Works on the Receiver’s Endon the Receiver’s End

The receiver accepts the photons and examines their The receiver accepts the photons and examines their modulation. If it matches the original one, the modulation. If it matches the original one, the encryption key is saved and used to decode data sent encryption key is saved and used to decode data sent over the network through conventional methods, such over the network through conventional methods, such as the Internet.as the Internet.

Martin Jasper of Boston University examines a single photon detector module.

Why Quantum Encryption Is Why Quantum Encryption Is NeededNeeded

Many researchers are currently trying to Many researchers are currently trying to develop quantum computers, which are develop quantum computers, which are believed to be capable of exponentially believed to be capable of exponentially greater computing power than today’s greater computing power than today’s supercomputers.supercomputers.

If quantum computers become a reality If quantum computers become a reality before quantum encryption does, before quantum encryption does, modern encryption methods could modern encryption methods could become obsolete.become obsolete.

Applications of Quantum Applications of Quantum EncryptionEncryption

Governmental and intelligence Governmental and intelligence operationsoperations

Financial and business transactionsFinancial and business transactions Personal encryption (files, e-mail)Personal encryption (files, e-mail) Many things no one’s thought of yetMany things no one’s thought of yet

More InformationMore Information

I found these websites useful.I found these websites useful. http://www.cs.caltech.edu/~westside/quantum-intro.htmlhttp://www.cs.caltech.edu/~westside/quantum-intro.html http://www.qubit.org/library/intros/crypt.htmlhttp://www.qubit.org/library/intros/crypt.html http://www.upscale.utoronto.ca/GeneralInterest/Harrison/Qhttp://www.upscale.utoronto.ca/GeneralInterest/Harrison/Q

uantTeleport/QuantTeleport.htmluantTeleport/QuantTeleport.html I found very useful an article from the Oct. 4, 2004 I found very useful an article from the Oct. 4, 2004 St. St.

Louis Post-DispatchLouis Post-Dispatch; a somewhat earlier version can ; a somewhat earlier version can be found at be found at http://www.nashuatelegraph.com/apps/pbcs.dll/article?AIDhttp://www.nashuatelegraph.com/apps/pbcs.dll/article?AID=/20040926/BUSINESS01/209260303=/20040926/BUSINESS01/209260303