Quantum Cryptography Leaving the Lab

Theodore Logan writes "More than a year ago, MagiQ announced the world's first commercial quantum cryptography system (pdf), with ID Quantique following closely in their footsteps. Currently, the technology is limited to offering point-to-point connections up to a maximum distance of around 50 km, but this is likely to be greatly improved on in coming years. The systems available today are prohibitely expensive for the average Joe (MagiQ's are priced at more than $50,000 per unit), but one could envision a future in which they are built into the infrastructure by non-end user actors. Does this spell the end of the field of cryptography? Will systems like this ever become commonplace, or will they be reserved for sensitive financial transactions and military applications? What impact will quantum cryptography have on society? Good articles available from International Herald Tribune, EE Times and CNET."

Comments

How easy is it to implement ?

[SloWave]

I've seen that regular geeks can build things such as quantum force microscopes in their own homes, how hard would it be for someone to build a quantum crypto system?

Uh Oh

[nate1138]

said Bob Gelfond, founder and CEO of MagiQ Technologies. "No
matter what advances occur in digital computing, quantum encryption can never
be deciphered, read or copied.

These kinds of statements always amuse me. It may be the toughest thing yet, but there's no saying that our understanding of some of the properties of quantum physics aren't flawed. Science may yet prove him wrong.

Wrong

[antientropic]

Reading datas alter them. So the man in the middle will be detected.

This is true for a passive attack, i.e., one were the attacker can only eavesdrop on a connection. However, in a man-in-the-middle attack, the attacker can also arbitrarily modify data. In particular you can have the following situation:

Alice <----> Eve <----> Bob

Here Alice thinks she is talking to Bob, but in fact she's talking to Eve, who decodes her packets, re-encodes them, and sends them to Bob. Unless Alice and Bob have some authentication mechanism (say, a shared secret key, or the other's public key), they have absolutely no way to tell that this is going on. The ability to detect eavesdropping on the quantum channel doesn't help at all, since Eve isn't eavesdropping - she's tunneling between two physically separate channels. Quantum cryptography does not differ in this respect from conventional cryptography: it's a basic fact of communication - how do you establish that the bits you are receiving come from the person/system from who you think they come?

Anecdote

[mark-t]

In the CS department at my school last year, all the students were encouraged to attend a particular lecture on quantum computing that was being given one day, and after the lecture one of my classmates was rather disturbed about some of the possibilities that quantum computing would enable, specifically quantum cryptography.

What I found rather peculiar about his view was that the reason he didn't like quantum cryptography was because it enabled organizations, such as a corrupt government perhaps, to be able to use this effectively unbreakable communication technique in order to avoid accountability to anyone else, while as long as encryption technologies remain crackable, there would always be some risk of being accountable to others for what they are communicating about.

It didn't even seem to matter to him that his own communications would be secure with this technology... he just didn't like the idea of technology introducing a break in a chain of accountability.