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One-Time Pad reinvented to make electronic copying impossible

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Re: One-Time Pad reinvented to make electronic copying impossible

#21

Post by ReidZB »

mc-lovin wrote: post #19
ReidZB wrote: post #15

Earlier quoted context omitted.

The original paper [1] is much clearer about the actual algorithm. The below is pretty much pulled straight from it, although I simplify it slightly (by assuming one pattern, etc.) First, Alice and Bob decide on a pattern P. Then they each compute a key K(A) and K(B) using the pattern P by shining P through their slab. Then, they publicly publish P and K(A) ⊕ K(B). (Apologies for the lack of good mathematical notatio…

Thanks, that's what I thought but I'm glad you confirmed it and put it in their notation. So here is my issue: Eve knows P, so she can steal the object and hence compute K(B). The difficulty in "copying" the object is only significant when Eve does not know P. But that same difficulty would apply if K(A) and K(B) were random numbers that Alice and Bob generated when they met. Or is the point that Alice and Bob genera…

Interesting point. I'm not sure what prevents Eve from simply computing K(B) from P if she has stolen Bob's slab. Maybe I have misinterpreted something?

The actual paper does describe generating n different patterns and then randomly selecting one of them to encrypt the message, but the index of the one that is randomly selected is sent with the encrypted message so that Bob can use it to look up the appropriate pattern. I took this as just generating more than one key for convenience's sake.

Notably, a requirement for security of the slab is that given temporary access, Eve "must not be able to efficiently copy or model its contents." So, I think the point is that since there are many different P's (and hence K(A)'s and K(B)'s), Eve cannot recreate K(B) for all P's in a reasonable amount of time. Further, she can't actually make a physical copy of the device. Still, it seems that if Eve can steal the device, she can break old messages --- which I guess is, as you said, a property shared by regular OTPs. When she steals the device, though, she can only decrypt so many messages before detection, since there is apparently a key recovery rate of 1.5 seconds per key.

But one of the other requirements set forth in the paper is that if the slab is stolen, Eve must not be able to send or receive messages. I'm not sure how that is fulfilled here.

Re: One-Time Pad reinvented to make electronic copying impossible

#22

Post by ReidZB »

graylights wrote: post #8

What's involved in the handling of this glass? They claim security because heating the glass damages its structure. A fingerprint or scratch would also damage it. Is it secure because it's just so fragile that it is plain unworkable in real world conditions? Also this article doesn't touch on whether the randomness generated is sufficiently random for cryptographic purposes. With enough error correction and an improp…

I'm not sure about the handling of the glass. The paper [1] gives all of the specific materials used in the experiment, but it doesn't say anything about handling them and I don't know enough about the area to be able to intelligently comment...

The paper also mentions that the randomness they are using passes the Diehard and NIST randomness tests, so it appears they are pretty random. Apparently, though, they have to sacrifice some of the bits in order to ensure that! It references "Supplements" E and F, saying they include more details, but they're not included in the arXiv paper. Of course, the original random patterns used to generate the keys are randomly selected too, so let's hope they're using a good random source for that...

[1]: http://arxiv.org/abs/1305.3886

Re: One-Time Pad reinvented to make electronic copying impossible

#23

Post by calhoun137 »

OT: If two people have to send a signal to each other, they should be named Alice and Bob, this goes back to Einstein's paper on the EPR paradox[1], and is based presumably on the fact that Alice starts with A and Bob starts with B.

Sometimes I read articles where Alice sends a signal to Charlie or something like that, and for me that is a huge red flag that indicates the author may not have payed much attention in school and/or may not have a great grasp on what they are talking about.

Fortunately this article is about Alice and Bob, so I am inclined to take it seriously.

[1] https://en.wikipedia.org/wiki/EPR_paradox

Re: One-Time Pad reinvented to make electronic copying impossible

#24

Post by rdtsc »

I don't understand, where is the beef?

How is this qualitatively different than a plain old symmetric encryption. Bob and Alice (or whatever and for whatever reason renamed characters in their example) each have the key, Alice encrypts ( ⊕ ) sends to Bob, he decrypts.

Is it the idea that the key cannot be digitally copied and instead it is two pieces of glass? How is it different than Alice and Bob using a one-time key for each transmission then destroying it (using secure wipe)? What if they use hand written papers to keep their keys and burn the pages when done.

I am probably being dense missing some deeper idea. Anyone care to explain?

Re: One-Time Pad reinvented to make electronic copying impossible

#25

Post by mc-lovin »

ReidZB wrote: post #21
mc-lovin wrote: post #19

Earlier quoted context omitted.

Thanks, that's what I thought but I'm glad you confirmed it and put it in their notation. So here is my issue: Eve knows P, so she can steal the object and hence compute K(B). The difficulty in "copying" the object is only significant when Eve does not know P. But that same difficulty would apply if K(A) and K(B) were random numbers that Alice and Bob generated when they met. Or is the point that Alice and Bob genera…

Interesting point. I'm not sure what prevents Eve from simply computing K(B) from P if she has stolen Bob's slab. Maybe I have misinterpreted something? The actual paper does describe generating n different patterns and then randomly selecting one of them to encrypt the message, but the index of the one that is randomly selected is sent with the encrypted message so that Bob can use it to look up the appropriate patt…

>But one of the other requirements set forth in the paper is that if the slab is stolen, Eve must not be able to send or receive messages. I'm not sure how that is fulfilled here.

If a "full" message involved both sides randomly picking a P, then this could still be satisfied.

But it doesn't seem to live up to my hopes for security: all it really guarantees is that the probability of Eve decrypting an intercepted message (assuming she steals the slab for time t and knows all the P's) is t/T where T is the time Bob and Alice spend generating K(B) + K(A) for different P's.

Re: One-Time Pad reinvented to make electronic copying impossible

#26

Post by duaneb »

calhoun137 wrote: post #23

OT: If two people have to send a signal to each other, they should be named Alice and Bob, this goes back to Einstein's paper on the EPR paradox[1], and is based presumably on the fact that Alice starts with A and Bob starts with B. Sometimes I read articles where Alice sends a signal to Charlie or something like that, and for me that is a huge red flag that indicates the author may not have payed much attention in s…

If only our scientific journals kept such rigorous academic standards.

Re: One-Time Pad reinvented to make electronic copying impossible

#27

Post by btilly »

rdtsc wrote: post #24

I don't understand, where is the beef? How is this qualitatively different than a plain old symmetric encryption. Bob and Alice (or whatever and for whatever reason renamed characters in their example) each have the key, Alice encrypts ( ⊕ ) sends to Bob, he decrypts. Is it the idea that the key cannot be digitally copied and instead it is two pieces of glass? How is it different than Alice and Bob using a one-time k…

The point is physical security and information density.

If you use an electronic one-time key and then secure wipe, you're not protected from someone who unbeknownst to you already read the contents of your hard drive.

If you use handwritten papers then you cannot store large amounts of data, nor is your data transmission rate anything feasible.

This allows an uncopyable object the size of a grain of sand to hold about a terabit of private shared data, and to process that at the speed that we can send/receive/react to light. (Considering that the basic technology is also used to send signals down fiber-optics cables, speed should be pretty good.)

Re: One-Time Pad reinvented to make electronic copying impossible

#28

Post by duaneb »

_void_star_ wrote: post #10
oofabz wrote: post #6

This is not a one-time pad. It uses a key that contains less information than the message. It is still possible to brute-force the key if you have enough data. It is a great way to make the key hard to copy, which is how encryption is usually circumvented in practice.

I'm not sure you right on this. The way I'm reading it they generate the keys by sending the same random signals through each set of glass. If they send N signals through the glass and N is >= the message length then it certainly is a one-time pad. The two keys end up being as long as (or likely longer than) the message, so you can't brute force it.

You're assuming that the structure of the glass can't be 'compressed' with assumptions about the structure of the glass.... At least the key space could be reduced well below the naïve entropy estimate.

Re: One-Time Pad reinvented to make electronic copying impossible

#29

Post by duaneb »

ovoxo wrote: post #20
ReidZB wrote: post #18

Earlier quoted context omitted.

The two slabs are actually different. See my explanation of the algorithm downthread: https://news.ycombinator.com/item?id=5741793

Ahh ok - great explanation btw. I'm still curious how this glass is produced. It seems to me that you would be introducing many more potential intrusion points by using physical encryptors since many more parties (people, databases, and systems) will be aware of the details in order to produce the appropriate slab. Having said that, the same thing would apply for any other physical encryptor that would have to be man…

I'm also interested in how they introduce quality entropy into the glass. It's well-researched algorithmically, but are material researches up to it? Even subtle patterns could lead to within brute-force distance.

Re: One-Time Pad reinvented to make electronic copying impossible

#30

Post by cynwoody »

calhoun137 wrote: post #23

OT: If two people have to send a signal to each other, they should be named Alice and Bob, this goes back to Einstein's paper on the EPR paradox[1], and is based presumably on the fact that Alice starts with A and Bob starts with B. Sometimes I read articles where Alice sends a signal to Charlie or something like that, and for me that is a huge red flag that indicates the author may not have payed much attention in s…

And then there's Eve, the evil one, the eavesdropper, the susceptible one in Genesis.
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