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First Bank Transfer via Quantum Cryptography
An anonymous reader writes with today's announcement that "the Austrian project for Quantum Cryptography made the world's first Bank Transfer via Quantum Cryptography Based on Entangled Photons; see also Einstein-Podolski-Rosen Paradoxon." (For more background, see the recent Slashdot post "Quantum Cryptography Leaving the Lab.")
Yes, but... what will I now need to decode my bank statements?
Wouldn't checking if the transfer went through alter your balance? :-P
...I can't observe my checking account balance without lowering it.
So the transaction slip presumably says:
Your transaction number has a 90% probability of being between 8765432 and 8765478.
Have a 75% nice day.
Craig Steffen
http://www.craigsteffen.net
Due to Insufficient Cat.
When in doubt, mod +1 funny and pray
... there has been a bank error in your favour. Collect $200. :)
..but why do we need this?
The biggest hole in security is usually the people operating technology. Ever want something, call up and ask for it.
What does the ability to have uncrackable encryption do to thwart social engineering tactics?
SIGERR: laziness exceeds quota
I'll give you my entangled photons in exchange for chocolate.
"If you think you have things under control, you're not going fast enough." --Mario Andretti
I'm asking this question again because it came a bit to late to the last discussion I posted it in
.1 photon to reduce the probability of generating a two-photon pulse that could be split and eavesdropped undetectably."
Is quantum crypto provably flawed?
I've seen tons of blurbs stating the the link is "absolutely" secure, but it seems that isn't really the case. (see the bottom of the page.)
What strikes me about all this is the following section:
"each pulse should be attenuated to an average of about
What that says to me is that there is not way to 100% know you're transmitting just one photon.
It sounds like there's no device that is capable of transmitting one and only one photon with 100% reliability. If this is the case, a lot of the arguments about how secure this is are vastly overstated.
In the end QC would be vulnerable to a man-in-the-middle attack by watching for multi-photon emissions.
If this is the case, a lot of the noise surrounding QC could turn out to be hype. (The big plus for quantum crypto is that it's supposedly immune to this.) Is there a quantum physicist in the house?
Life is too short to proofread.
Nah, back to those good ol' electrons.
"I may know how to program with code, but damned if i know how futons work!"
Simple: fold the futon up when you want to use it as a couch and then fold it back down when you want to use it as a bed.
Bruce Schneier covered why quantum cryptography doesn't solve any security/secrecy problems in his December 15, 2003 Crypto-Gram.
"It's like defending yourself against an approaching attacker by putting a huge stake in the ground. It's useless to argue about whether the stake should be fifty feet tall or a hundred feet tall, because the attacker is going to go around it. Even quantum cryptography doesn't "solve" all of cryptography: the keys are exchanged with photons, but a conventional mathematical algorithm takes over for the actual encryption."
The reason that the man-in-the-middle attack doesn't work is that by doing so, you introduce two sets of attenuation rather than one. If the message is intercepted and then re-transmitted, the message has now been sent through the attenuation cycle twice. This means that instead of the signal being modified by the original attenuation function, it's modified by the attenuation function squared, which is easy to distinguish.
Craig Steffen
http://www.craigsteffen.net
because you wouldn't know which photons contain the data. as soon as you touch it, the other end knows it's datastream has been tampered with.
This is a good overview.
I post links to stuff here
Yeah, but filling out the slip for "1/sqrt(2) |deposit> - i/sqrt(2) |withdrawal>" is a pain, and thanks to the epoch of inflation my balance is now much smaller than the rest of the universe... luckily, even in an income vacuum my balance randomly jumps up, but only for REEEEAAALLLLYY short lengths of time. I've been hawking radiation for a while but everyone says it's just a two slit operation.
Okay, I'm done now.
[TMB]
Yes and no. (Well, we *are* talking quantum stuff here, aren't we?) Do a google for "bell inequality" and see if you can get anything from the results. Basically, the answer is , yes, it is instantaneous. And no, it doesn't violate the speed-of-light limitation because you cannot get any useful information transmitted that way. You see, there are two photons which are interlocked. The first photn came at the speed of light and it contains the information you are looking for. The second photon, which serves to validate the quantum key is redundant from the information point of view, it doesn't carry the bank account balance, it only serves to detect tampering in the system.
In order to "read" the photon, you will need to measure the polarization of that photon. But, due to quantum mechanics, as soon as you measure the polarization (for example, with a filter), you will in effect have changed its polarization, and thus its original, actual polarization will be unknown to you. And that's the trick. In essence, the message is "read once." Even if you happen to use the exact same filter as the sender, and read the original photon (and message) for yourself, you can not retransmit the photon with its original, actual polarization -- and thus your "clean one" will arrive at the destination as garbage (thus notifying the receiver that the message has been compromised).
For more info read this primer.
First, Schneier really loves his stake-in-the-ground idea. He used it to describe cryptography in general in his "Secrets and Lies" book (which, IMHO, doesn't hold a candle to the quality of his applied crypto books. In fact, it feels more like a book-long commercial for his managed security business)
Anyway, sure. QC alone ain't gonna help you. But if it's a stake in a ground that's part of a fence, it damn well matters if it's 100 ft tall vs 1 ft tall, or even 10 ft tall.
Does it 'solve' security problems? No, of course not, because as many many many people have already said, in this post and in many other places, the way to defeat the best crypto in the world is to look under a keyboard and copy down the relevant password/phrase that the user wrote on a sticky-note there. (or other social engineering tricks)
It does make security easier, as it prevents MITM attacks, requires (for now) specialized hardware, and provides really-tough-to-decode crypto. So, if you have the rest of your process working, yes, QC can help by being a more secure technology.
But think of the inverse. OK, so, crypto is like a stake in the ground, it doesn't matter what size or where it is. So, let's all use DES, because it's an established standard!
You are only as secure as your weakest link, obviously. You'd be stupid if crypto turns out to be your weakest link, as even not counting QC, there's lots of good, secure crypto processes available.
Returned Peace Corps IT Volunteer
Don't look to closely at your account balances, lest they become more uncertain.
Yes, Quantum Cryptographic Communications (QCC) can help with the requirement that the one-time pad must be transmitted in private. However the one-time pad cannot be reused so your key must be the same size as your text. Thus far, Quantum Cryptographic Communications is not a speedy high bandwidth form of communication. It might be OK to transmit a small key but to date it is not OK for sending, in a reasonable period of time, huge one-time pad keys that are as big as your original message.
Another thing people sometimes gloss over about Vernam one-time pads is that your cipher is only as good as your random number generator! If you generate your one-time pad using the v7 libc rand(3) function your one-time pad is next to useless.
Another important aspect of Quantum Cryptography (Quantum Cryptography is not simply limited to communications) is random number generation. Quantum Cryptographic Random Number Generation (QCRNG) is a useful tool in generating keys (one-time pads, block cypher keys, public/private key pairs, etc.).
The importance of QCRNG goes beyond Vernam one-time pads. You want a cryptographically strong RNG such as a QCRNG when you generate your session keys. Sending predictable keys over a QCC protected link is next to useless!
Now IF you have:
then you will begin to approach the ''unbreakable cypher level'' that some people think you get with Vernam One-Time Pad Ciphers.
chongo (was here)
OK, I am not a believer in quantum cryptography for one big reason -- fiber loss. Someone please enlighten me if I'm wrong.
The loss of standard single-mode fiber is about 0.1-0.2 dB/km. Therefore, unless the distance is short (as in this demonstration), the transmitter must send multiple photons to ensure a decent probability of providing the receiver with one photon.
For example, if the span is 100 km long (20 dB loss), then on average only 1 out of every 100 transmitted photons will reach the receiver.
The situation is worse for autocompensating quantum-crypto systems (e.g., polarization-based encoding), because the photons must survive a round trip through the fiber.
Therefore, the relatively high power at the transmitter implies that an attacker can tap into the fiber near the transmitter, subtract (on average) only 1 photon, and remain undetected by the receiver.
Furthermore, typical optical amplifiers add noise (3 dB noise figure for your standard erbium-doped amplifier). The added noise photons would screw up the link, so amplifiers are out.
In the end, it seems to me that quantum crypto is good for table-top demos, and maybe for short jaunts across a metro area. But it is NOT absolutely perfect, at which point computationally difficult encryption is more attractive.