I know this is pretty obscure, but here we go...

BBC: Quantum Cryptography Breakthrough

If measuring an actual polarised light particle changes its state - how can you route it through a network without accidentally measuring it?

The Italians were using a private network I believe that was directly connected.

Discuss.

# Quantum Cryptography

Page 1 of 1## 11 Replies - 2145 Views - Last Post: 24 October 2008 - 01:07 PM

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**Replies To:** Quantum Cryptography

### #2

## Re: Quantum Cryptography

Posted 11 October 2008 - 04:28 PM

if somebody got the key(say the timing of the photons) couldn't they make their attack and then adjust their broadcast accordingly and send to the next node without them detecting the breach?

### #3

## Re: Quantum Cryptography

Posted 11 October 2008 - 06:10 PM

It really doesn't sound like cryptography. Cryptography generally functions on the premise that the message will be intercepted, and then figures out how hard it is for outside party to decode the message without some vital bit of information.

Here, you're talking about obscurity through quantum entanglement. Basically, if I have a pair of telepathic twins. Each twin knows what the other is thinking, regardless of distance of separation. It's an absolutely private communication, no one else can tune in. It's very secure. It's hard to call it encrypted.

Here, you're talking about obscurity through quantum entanglement. Basically, if I have a pair of telepathic twins. Each twin knows what the other is thinking, regardless of distance of separation. It's an absolutely private communication, no one else can tune in. It's very secure. It's hard to call it encrypted.

### #4

## Re: Quantum Cryptography

Posted 11 October 2008 - 08:50 PM

but doesn't it become encryption because a "key" is need to translate the light signal into a message? Just asking, not sure if I'm talking rubbish or not

### #5

## Re: Quantum Cryptography

Posted 12 October 2008 - 01:31 AM

The point is, is that it functions in a similar way to public-key encryption which derives its major weakness from the problem of key distribution. This method is called cryptography as the text is encrypted using the information from the entangled photons - which would yield the public key; therefore the encryption is strong because it is so difficult to intercept.

As for the MITM attack, the entagled photon(s) are impossible to copy, the actual public key is never transmitted, it travels faster than the speed of light (for some unknown reason) - so similar to the telepathic twins. It is impossible to influence the state of the two entagled photons from an outsiders perspective.

Plus the message can actually be standard TCP/IP communications while two people have the entangled photons as they can still calculate the public key.

As for the MITM attack, the entagled photon(s) are impossible to copy, the actual public key is never transmitted, it travels faster than the speed of light (for some unknown reason) - so similar to the telepathic twins. It is impossible to influence the state of the two entagled photons from an outsiders perspective.

Plus the message can actually be standard TCP/IP communications while two people have the entangled photons as they can still calculate the public key.

This post has been edited by **homemade-jam**: 12 October 2008 - 01:32 AM

### #6

## Re: Quantum Cryptography

Posted 12 October 2008 - 07:31 AM

I thought if anything traveled faster than the speed of light it went backwards in time. Curse you futurama for lying to me!

### #8

## Re: Quantum Cryptography

Posted 13 October 2008 - 12:30 PM

It only slows time down, doesn't allow you to travel backwards. It appears as though to get somewhere faster than the speed of light, somehow, it must pass through dimensional space that's at least 1 more dimension than we live inside. Only real theoretical physicists can explain if any of these are correct, but it looks like "folding space" is the way.

Using a 1-dimensional model, curving a line so that it intersects creating a single point so that objects can jump the distance in an instant. In 2-dimensional space, the gate is a line and in 3-dimensional space, it would be some 2D plane... This has to have been thought about before, and it would be pretty convenient for a theoretical physicist to explain this idea (whether they agree or not) much better.

Using a 1-dimensional model, curving a line so that it intersects creating a single point so that objects can jump the distance in an instant. In 2-dimensional space, the gate is a line and in 3-dimensional space, it would be some 2D plane... This has to have been thought about before, and it would be pretty convenient for a theoretical physicist to explain this idea (whether they agree or not) much better.

This post has been edited by **WolfCoder**: 13 October 2008 - 12:35 PM

### #9

## Re: Quantum Cryptography

Posted 16 October 2008 - 10:43 AM

Quantum Cryptography can be cracked, but it isn't easy.

Emergent Chaos

'Unbreakable' quantum cryptography hacked without detection using lasers

Emergent Chaos

'Unbreakable' quantum cryptography hacked without detection using lasers

### #10

## Re: Quantum Cryptography

Posted 17 October 2008 - 10:49 AM

For those hanging on every thread of this err thread..

Quantum Cryptography is Pointless

Ready this article has just managed to really pee me off - it would be some guy from BT to piss on the bonfire of some scientists that managed to enact only what he could dream. He just manage to get his plug in for his outdated book and is really bitter that he didn't get a mention on the bbc website. He works at BT - the most boring of all telephony companies who can barely support a UK broadband service let alone work with any sort of research type project.

[/rant]

Quantum Cryptography is Pointless

Ready this article has just managed to really pee me off - it would be some guy from BT to piss on the bonfire of some scientists that managed to enact only what he could dream. He just manage to get his plug in for his outdated book and is really bitter that he didn't get a mention on the bbc website. He works at BT - the most boring of all telephony companies who can barely support a UK broadband service let alone work with any sort of research type project.

[/rant]

This post has been edited by **homemade-jam**: 17 October 2008 - 10:54 AM

### #11

## Re: Quantum Cryptography

Posted 19 October 2008 - 12:32 AM

I agree with baavgai that this is not cryptography so much as a secure communications channel.

BTW there is a well know "unbreakable" cryptography scheme out there for many years. Here unbreakable really just means that the security is 100% in the key. As long as the key is only known by the sender and the receiver than no one else can read the message.

A true one time pad can ONLY be decrypted with the key. However it has two problems. #1 the key must be truly random (pseudo random is not good enough). #2 the key must be securely transferred from the encryption station to the receiving station.

It looks like this "quantum cryptography" is really just a secure channel. It would not be of use for digital storage.

BTW there is a well know "unbreakable" cryptography scheme out there for many years. Here unbreakable really just means that the security is 100% in the key. As long as the key is only known by the sender and the receiver than no one else can read the message.

A true one time pad can ONLY be decrypted with the key. However it has two problems. #1 the key must be truly random (pseudo random is not good enough). #2 the key must be securely transferred from the encryption station to the receiving station.

It looks like this "quantum cryptography" is really just a secure channel. It would not be of use for digital storage.

### #12

## Re: Quantum Cryptography

Posted 24 October 2008 - 01:07 PM

Another interesting breakthrough, this time in Storage of Qubits - finally there is the prospect of some sort of useful memory for the storage of Qubits, inside nuclei!

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