Relativity Used to Devise New Form of Crypt

Cebert writes "CNN.com posted an article about using relativity to create a new form of encryption. The new encryption allows an individual to make a prediction with a guaranteed date stamp that only they can reveal. " Hmmm...quantum predictions. Yeah, I guess that's hard to crack.

Here are a few more details

[VanL]

The article is a little short on facts. Here are a few more details:

ABSTRACT:
Unconditionally Secure Bit Commitment

Adrian Kent
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW, United Kingdom

(Received 13 July 1998)

We describe a new classical bit commitment protocol based on cryptographic constraints imposed by special relativity. The protocol is unconditionally secure against classical or quantum attacks. It evades the no-go results of Mayers, Lo, and Chau by requiring from Alice a sequence of communications, including a postrevelation verification, each of which is guaranteed to be independent of its predecessor. ©1999 The American Physical Society
Here are copies of his article in pdf [aip.org] and in gzipped PS [aip.org].

I

Is this for real?

[Taco Cowboy]

Or is it yet another ploy to get us all excited for nothing?

I've read too many of the pie-in-the-sky things that I think I am becoming more and more cynical by the day.

Try this instead

[bholzm1]

Here's the preprint in ps [lanl.gov] from LANL, instead; only institutional subscribers have access to the PRL online article.

Protocol to secure REAL TIME communication only

[yabHuj]

I read from the article (e.g. the Postscript version [lanl.gov] of the original article on LANL), that this protocol can only be used to secure real time communications only.

The protocol cannot be used for email or file encryption. With this protocol one can only make sure, that the line you are currently using is secure.

As timing is a critical of the security mechanism, standard internet with nondeterministic transmission times does not qualify for this protocol.

Nonetheless an interesting article (and as "smooth" to read as any other scientific article).

#define rant_mode
A classic case of hearsay (=RTFM failure) and media hype.
#undef rant_mode

Re:Excuse me,

[conform]

dude! imagine quake3arena on a beowulf cluster running einsteinian-crypto-based 1GHz Athlons!

how many fps do you think it would get!?!!

Re:Is this for real?

[PD]

The Physicist who made the announcement was named Kent. If this is the same Dr. Kent that I've heard of before, he is a real researcher, and he's somewhat famous.

It is a logical fallacy to believe that just because the announcement was made by Dr. Kent that it must be true. Dr. Kent could possibly be releasing a bogus announcement to have a joke on the rest of us.

But, knowing the stature of Dr. Kent I can reasonably presume that Dr. Kent is most likely NOT having a joke on us, so any suggestions that this is bogus science should be withheld for now.

Watch out for those wormholes

[foobarbazquux]

Admittedly, I was a tad sceptical about all this but it does seem to be right. For real-time communications only, of course.

A caveat: If there exists a wormhole between A and B such that the time taken from A to B is 'subverted' to be smaller than expected, the whole system breaks down.

So in effect, you have to check that the local space between A and B is Minkowski-like before communicating. Or just trust!

Exponentiality problem

[Randym]

As its implementation requires channel capacity that, for a fixed separation [of users' locations], increases exponentially with the commitment time, it is not a practical solution to the problem of long-term bit commitment.

Well -- yeah. It works because nothing is revealed until everything is revealed, as it were. It collapses to the concepts: 1)that you can't decrypt a message until you receive all the bits of it + 2)one-time pad. It introduces the additional complication of communication between users (that's where relativity comes in -- the light cone limits transmission speed, but the authors very gracefully fold in the idea of quantum communication and classical communication being identically undecryptable under this protocol.) Clever, but [currently] useless.

----------

This is *not* a form of encryption

[Paul Crowley]

Contrary to the report, this doesn't encrypt anything: it's a "bit commitment" protocol, allowing me to irrevocably choose one of two choices without revealing what I chose later. One application of this is fair coin tosses: you and I both choose a bit at random, then reveal them once they're chosen, and if they're the same I win otherwise you win. The commitment protocol stops me waiting until you've revealed your choice and then announcing that mine is the same.

As another poster said, in practice SHA message digests can be used to do the same job more practically, but this offers "unconditional security"; no amount of computing power could be sufficient to break the protocol.
--

Re:Is this for real?

[MindStalker]

Umm, maby its just me, but I didn't think we figured out faster than light messaging yet between planets, but then again, maby I'm wrong.

Great for patents and prior art

[petdr]

This should have implications for patents and prior art, as now you can reliably date stamp a piece of code as to when it was created.

Pete.

Login difficulty

[The Wookie]

Unfortunately, this scheme presents a problem, because when using quantum encryption, it is not possible to know both your user name and password at the same time.

Not to mention the fact that someone keeps killing /bin/cat.

Re:Don't look!

[SkipRosebaugh]

If, however, you look and find that it is dead, simply get enough other people to look until one of them sees it alive, then the whole problem is solved. At least, according to this one sci-fi story I read, it is, I think. Or, you could go the Dirk Gently route, instead.

Re:Is this for real?

[Bloater]

You don't have to be faster than light. Lets say you are sending a message to mars when it is just coming into view on the other side of the sun. You start sending your message at the speed of light (a radio signal), and you must finish within 20 minutes (the time it takes for the start to reach the destination at light speed).

--

Re:Login difficulty

[CynicX32]

> Not to mention the fact that someone keeps killing /bin/cat.

Actually, I'm not sure whether mine's dead or alive. I'd better go check...

ryan

air

[RoLlEr_CoAsTeR]

It is strange how oftentimes the air speaks. We are sane as long as we hear voices where there are none. We are insane when we hear nothing, and worse, we are
Indeed.... a most interesting observation.

Of course, hearing nothing when we are "hearing" something could be attributed to deafness...

Re:Is this for real?

[Hard_Code]

"It requres the ability to send meaningfully large messages in less than the propogation time of light between two parties."

Um...wouldn't being able to send messages in less than the propigation time of light mean that the messages would have to be going faster than light?? Sure...the impossible is uncrackable...

Re:Is this for real?

[Neil Rubin]

I'm sure that the requirement is that the end of the message be sent before the beginning could arrive traveling at the speed of light.

This is easy to achieve when communicating between planets, for example, but 100 Mps Ethernet between adjacent buildings would only manage messages a few bits long.

Don't look!

[Kaa]

> Not to mention the fact that someone keeps killing /bin/cat.

Actually, I'm not sure whether mine's dead or alive. I'd better go check...

Don't go and check! Until you look your /bin/cat is in superimposition of states and so works OK. As soon as you check, the wave function collapses and you have a chance of getting a dead /bin/cat!

Disclaimer: this assumes a Copenhagen interpretation. If you like multiple universes better, you can check your /bin/cat without any problems -- nothing more serious than forking of the whole universe is likely to occur.

Kaa