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RECENT POSTS IN THIS TOPIC

Eckard Blumschein: on 12/30/11 at 19:05pm UTC, wrote Peter, I appreciate you confirming simultaneity. The reason for Poincaré...

Peter Jackson: on 12/30/11 at 13:07pm UTC, wrote Eckard I interpret Poincare as Georgina's thesis. Sure he was groping in...

Eckard Blumschein: on 12/30/11 at 0:02am UTC, wrote Peter, E.g. he wrote in II: "psychologic time is given to us and must...

Peter Jackson: on 12/29/11 at 12:10pm UTC, wrote Eckard I hope you are not attribute the 'many mistakes' to Poincare. I...

Eckard Blumschein: on 12/27/11 at 23:37pm UTC, wrote The link to Einstein synchronization led me to not just what I consider...

Domenico Oricchio: on 12/23/11 at 18:24pm UTC, wrote A secure cryptography can be a numerical entanglement without quantum...

George Musser: on 12/15/11 at 22:08pm UTC, wrote When a speaker brings a tangle of garden hoses, a bottle of water, and a...


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July 17, 2019

CATEGORY: Blog [back]
TOPIC: Proving You Are Where You Say You Are: Position-Based Quantum Cryptography (Part I) [refresh]
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Blogger George Musser wrote on Dec. 15, 2011 @ 22:08 GMT
When a speaker brings a tangle of garden hoses, a bottle of water, and a towel to the podium, you know it’s going to be a fun talk. Computer scientist Harry Buhrman of the Centrum Wiksunde & Informatica in Amsterdam recently visited Singapore to help celebrate the fourth anniversary of the Centre for Quantum Technologies. He and his props gave quantum cryptography a whole new dimension--literally. Instead of encrypting a message or authenticating someone’s identity, Buhrman posed a deceptively simple question: Can someone be sure you are where you say you are?

Figure 1
Figure 2
Position verification isn’t just of interest to spouses who wonder about all those late nights at the office. It would tighten up secure communications channels and make it possible to send Mission Impossible-style messages that could be read only if someone visited a certain location (like geocaching puzzles). For fundamental physicists, the procedure raises an important question about the operational meaning of space. If you cannot confirm, even in principle, whether something is at a given location, does the concept of location have any objective meaning? In fact, the scenario Buhrman laid out bore a spooky resemblance to the holographic principle in quantum gravity.

Imagine trying to confirm your position in one dimension, along a straight line (Figure 1). A verifier can use the procedure of Einstein synchronization: send you a signal, to which you reply, and measure the round-trip time in order to gauge the distance between the two of you. It is the maximum distance; you might be closer, given the delays that could arise in the process. To narrow down your location, a second verifier on the opposite side of you also sends a signal that you must reply to. This technique goes by the name of distance bounding.

It’s easy to game the system, however (Figure 2). Two comrades intercept the signals, wait a short while (to simulate the travel time to your purported position), and reply on your behalf. Now you don’t need to be where you claim to be. With your friends covering for you, you can safely leave the office and have your affair.

(Images courtesy of Harry Buhrman.)

More nefarious scheming in the second part of this post, where things get quantum...

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Domenico Oricchio wrote on Dec. 23, 2011 @ 18:24 GMT
A secure cryptography can be a numerical entanglement without quantum device.

I think that is possible a quantum entanglement simulation without quantum device using a simulation of a wave function, in common between transmitter and receiver.

A wave function can be transformed in a infinite binary code in two computers, then it is possible an equal string generator in the receiver and transmitter (common wave function with some sync emission): it is necessary an infinity of binary string to obtain a secure code (I think that is possible to take the not integer part of the real number like digit-the starting point must be the first one in the string); I think an hypothetical polynomial equation, with integer parameters and real solution (transformed in binary string), with infinite binary string like solution, or some real number obtained like pi using some simple equation, or some fractal generators (random generators).

It is necessary a transmission function (wave function modification) using a binary function (infinite random string common in receiver and transmitter) in receiver and transmission (I think an extension of OR, AND and XOR function) that transform the channel in a bidirectional channel: it is necessary to use the string to exchange the order of all the possible different outputs using the infinite transmission function like exchange function (one output of the function with a single input wave function and a single data transmission, and a measure function that change ever).

It seem that this method is perfect for a bidirectional streaming, and it seem that many cryptographic analytic method are included in this numerical method.

It is only a theoretical method, and I have not evaluated now all the system complexity.

Saluti

Domenico

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Eckard Blumschein wrote on Dec. 27, 2011 @ 23:37 GMT
The link to Einstein synchronization led me to not just what I consider ridiculous efforts to discuss conceptuality of synchrony from the view point of SR instead of questioning the latter. I also found a rather poor but perhaps nonetheless helpful translation of Poincaré's 1898 paper La mesure du temps.

It can be considered as a guide to many mistakes that are still affecting physics.

Eckard

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Peter Jackson wrote on Dec. 29, 2011 @ 12:10 GMT
Eckard

I hope you are not attribute the 'many mistakes' to Poincare. I agree ha made as many as anybody, but his logic seems so far not to have been falsified;

1897; "Whoever speaks of absolute space uses a word devoid of meaning." and; 1898 'Mesure du Temps'; “We do not have a direct intuition for simultaneity, just as little as for the equality of two periods. If we believe to have this intuition, it is an illusion. We helped ourselves with certain rules, which we usually use without giving us account over it [...] We choose these rules therefore, not because they are true, but because they are the most convenient."

1905; Academy of Sciences Paris 5 June; "...the space revealed to us by our senses is absolutely different from the space of geometry." and;

"what one may call the local time... as demanded by the relativity principle the observer cannot know whether he is at rest or in absolute motion."

Surely light also cannot 'know' of any state of motion of any local field with respect to any other when not interacting. Is any other logic possible?

It may seem that this can both prove the SR postulates AND allow 'Local Reality', consistent with Stokes and Shtyrkov. Light simply changes speed to local c on arrival and interaction with matter, as found in Chandrasekhara Raman's 1930 Noble winning paper. Is there any evidence inconsistent with this?

Best wishes

Peter

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Eckard Blumschein replied on Dec. 30, 2011 @ 00:02 GMT
Peter,

E.g. he wrote in II: "psychologic time is given to us and must needs create scientific and physical time". In my understanding, the quantity elapsed time is objectively measurable, and we must not at all relate it to psychology, consciousness, intuition, "great consciousness which should see all", "imperfect god", etc. Why dealt Poincaré with such subjective and speculative aspects?

Obviously he did not quite understand the role of abstract notions. He was a brilliant and prolific writer (about 30 textbooks and more than 500 papers) rather than really in position to prove Cantor wrong. I read, he called Cantor a charlatan and uttered: Future generations will consider set theory an illness from which they were cured.

He always used the expression "in time" because he ignored the distinction between measurable in principle time and the construct of a timescale without beginning and without an end.

He argued in VIII: "Is not my present nearer my past of yesterday than the present of Sirius? It has also been said that two facts should be regarded as simultaneous when the order of their succession may be inverted at will. It is evident that this definition would not suit two physical facts which happen far from one another".

To me it is almost unbelievable: This ridiculous mistake of Poincaré seems to be the basis for the claimed denial of simultaneity.

I will break here for today.

Best,

Eckard

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Peter Jackson wrote on Dec. 30, 2011 @ 13:07 GMT
Eckard

I interpret Poincare as Georgina's thesis. Sure he was groping in the dark, as they all were then including Lorentz, and I don't understand the quotes you give, but consider this scenario, which demonstrates the point that apparent (as all we can see is the apparent) elapsed time is not directly objectively measurable except in very unique and almost impossible circumstances;

Take a lightship emitting flashes at three second intervals. These are observed by three people. They will all measure different time intervals!

This is because one is on a ship receding, one on a plane approaching and one at rest on the shore. Yes it is simple, although the one on the shore may confuse, but not only may the lightship be adrift, but a strong wind will either reduce or dilate the period as n=1.0003 for air is a constant.

The point, and one of which Poincare was considering, is that also in a vacuum in space, any relative motion between emitter and observer changes the observed (i.e. measured) interval.

In the end it was Einstein who copied much but ignored some important parts of Poincare's hypothesese in 'painting himself round the room and into the corner' with SR.

I suggest simultaneity is however apparently always simply calculable with the correct data, including distance, relative motion in any medium and the n of the medium, by using c. Spectroscopy assists.

Peter

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Eckard Blumschein replied on Dec. 30, 2011 @ 19:05 GMT
Peter,

I appreciate you confirming simultaneity. The reason for Poincaré to leave the path of sound thinking seems to be obvious: He admired Lorentz, and like Lorentz and all other physicists he was unable to reasonably explain the result by Michelson and Morley. It does not matter whether e.g. Einstein, Georgina, and many others got aware of this, they all felt forced to arrange with a interpretation of the result by M&M which has been erroneously believed compelling while actually the result of M&M does neither disprove nor prove an ether. It is simply wrongly designed.

Incidentally, Poincaré uttered the same ultrafinitist anti-Cantor attitude as nowadays does Prof. Wolfgang Mueckenheim, who is blamed a crackpot for the same: There is no perfect infinity. Already Aristotle meant: Infinitum actu non datur. I consider this position in physics acceptable while, of course, the actually infinite sum 1/2 + 1/4 + 1/8 +... = 1 is correct mathematics.

Eckard

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