Optical boffins cut the cost of quantum cryptography

Time shift dances the light fantastic

The essential guide to IT transformation

Boffins at the National Institute of Standards and Technology are trialling advanced optical techniques aimed at reducing the price of quantum cryptography systems.

The new quantum key distribution approach reduces the required number of single photon detectors, which can cost anything between $5K-$20K and are the most costly component of quantum cryptography systems.

Quantum cryptography allows two users on an optical fibre network to exchange secret keys. Each bit of the key is encoded upon a single light particle (or 'photon'). Intercepting this data randomly changes the polarization of the light, irreversibly altering the data.

Because of this quantum mechanics effect any attempt by an eavesdropper to determine a key corrupts the same key with noise. Quantum cryptography systems discard these corrupt keys and only use codes that are known to be secure. These quantum keys, once exchanged, can be used in a one-time pad.

Conventional cryptography setups involve at least two photon detectors, and more commonly four. By adding an optical component that delays the travel of photons to the detector, NIST researchers have been able to halve the number of detectors needed.

The most common polarization-based protocol, BB84, uses four single-photon detectors. One pair of detectors looks for photons with either vertical or horizontal polarization, which signify either 0 or 1. The other set of detectors record diagonally polarized photons.

NIST researchers have reduced the number of detectors required by using an optical component to make these diagonally polarized photons rotate by a further 45 degrees and arrive at the horizontal/vertical detector, but slightly later than photons that started off with this orientation. As such the approach is a type of time division multiplexing.

The same technique was used to number of detectors needed to implement the B92 protocol from two to one.

The approach cuts transmission rates by half but the advantage of lower costs far outweighs this minor disadvantage. The NIST team, led by researcher Xiao Tang, reckon the approach avoids introducing noise and might actually be more secure than conventional approaches.

NIST researchers intend to explain their detection time bin shift (DTBS) scheme in a paper due to be published by the IEEE Communications Letters next month.

In additional research carried out after the publication of this paper, the NIST team has further developed its approach so that the popular BB84 protocol requires only one detector instead of four.

A summary of the research, including diagrams, can be found on the NIST website. ®

Next gen security for virtualised datacentres

More from The Register

next story
Snowden on NSA's MonsterMind TERROR: It may trigger cyberwar
Plus: Syria's internet going down? That was a US cock-up
Who needs hackers? 'Password1' opens a third of all biz doors
GPU-powered pen test yields more bad news about defences and passwords
e-Borders fiasco: Brits stung for £224m after US IT giant sues UK govt
Defeat to Raytheon branded 'catastrophic result'
Microsoft cries UNINSTALL in the wake of Blue Screens of Death™
Cache crash causes contained choloric calamity
Germany 'accidentally' snooped on John Kerry and Hillary Clinton
Dragnet surveillance picks up EVERYTHING, USA, m'kay?
Linux kernel devs made to finger their dongles before contributing code
Two-factor auth enabled for Kernel.org repositories
prev story


5 things you didn’t know about cloud backup
IT departments are embracing cloud backup, but there’s a lot you need to know before choosing a service provider. Learn all the critical things you need to know.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Build a business case: developing custom apps
Learn how to maximize the value of custom applications by accelerating and simplifying their development.
Rethinking backup and recovery in the modern data center
Combining intelligence, operational analytics, and automation to enable efficient, data-driven IT organizations using the HP ABR approach.
Next gen security for virtualised datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.