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Author Topic: IOTA  (Read 988323 times)
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tromp
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November 16, 2015, 04:33:59 PM
 #661

Computing a single bit of a hash is almost as much effort as computing the whole hash; you might be saving a percent or two at most.

Could you provide a proof of this statement?

Thus follows directly from how SHA256 is defined.
It is many rounds of confusion and dispersion;
so that each single bits in one round depends on pretty much all bits of previous rounds.

Quote

That is a long document to read. Where exactly does it claim that?
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tromp
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November 16, 2015, 04:37:39 PM
 #662

But Hashcash with large memory requirements will likely not be affected as long as scaling quantum computers up to millions of bits remains elusive.

I didn't find information on time-memory trade-off of quantum computers, but if we assume that the trade-off is not worse than the trade-off of classical computers then we get that memory increase of the hashing function can be counteracted by increasing time we run the computations. So Hashcash with large memory won't save us.

Of course I was talking about hash-functions that don't allow for time-memory trade-offs.
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November 16, 2015, 05:21:04 PM
 #663

Of course I was talking about hash-functions that don't allow for time-memory trade-offs.

Give me the name of one of such functions, please. The trade-off is a pretty universal thing, the best a function can do is to keep time*memory*advice constant, if I'm not mistaken.
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November 16, 2015, 05:27:47 PM
 #664

so that each single bits in one round depends on pretty much all bits of previous rounds.

This means that after some number of rounds SHA256 doesn't give a better mixing, hence it's possible to do a shortcut by finding a polynomial with fewer number of operators.


That is a long document to read. Where exactly does it claim that?

Quote
I introduced a novel algorithm to solve the bitcoin mining problem without using (explicit) brute force. Instead, the nonce search is encoded as a decision problem and solved by a SAT solver in such a way that a satisfiable instance contains a valid nonce. The key ingredients in the algorithm are a non-deterministic nonce and the ability to take advantage of the known structure of a valid hash using assume statements.

A couple of benchmarks demonstrated that already with simple parameter tuning dramatic speed ups can be achieved. Additionally, I explored the contentious claim that the algorithm might get more efficient with increasing bitcoin difficulty. Initial tests showed that block 218430 with considerably higher difficulty is solved more efficiently than the genesis block 0 for a given nonce range.

This means that in average computation of a single bit takes less time than computation of the whole hash.
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November 16, 2015, 06:25:11 PM
 #665

Of course I was talking about hash-functions that don't allow for time-memory trade-offs.

Give me the name of one of such functions, please. The trade-off is a pretty universal thing, the best a function can do is to keep time*memory*advice constant, if I'm not mistaken.

You are quite mistaken. This is a recognized weakness in scypt's design.

Here's one: Argon2, winner of the Password Hashing Competition.

Most of the PHC candidates qualify, since time-memory-trade-off resistance was one of the design goals.
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November 16, 2015, 06:41:47 PM
 #666

This means that in average computation of a single bit takes less time than computation of the whole hash.

Like I said it takes a about a percent less.

All that article does is propose an extremely inefficient way of evaluating SHA256,
as some of the comments there already point out.

You should find more reputable sources to support your questionable claims.
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November 16, 2015, 06:47:36 PM
 #667

Here's one: Argon2, winner of the Password Hashing Competition.

Argon2 whitepaper says that time-memory trade-off still can be used. At some point the trade-off stops working because computational units will occupy more space than the removed memory but this protection won't work for a quantum computer with its perfect parallelism of computations. Looks like Argon2 fails to deliver protection against quantum computers.
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November 16, 2015, 06:55:56 PM
 #668

You should find more reputable sources to support your questionable claims.

There are not that many papers that analyze algebraic attacks on double SHA256. Look at http://link.springer.com/chapter/10.1007%2F978-3-642-21702-9_6#page-1 and https://bitcointalk.org/index.php?topic=265759.msg2851659#msg2851659 to get understanding how single bits can be computed faster than computation of the whole hash. https://en.wikipedia.org/wiki/Algebraic_normal_form may also help.
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November 16, 2015, 07:07:40 PM
 #669

Here's one: Argon2, winner of the Password Hashing Competition.

Argon2 whitepaper says that time-memory trade-off still can be used. At some point the trade-off stops working because computational units will occupy more space than the removed memory but this protection won't work for a quantum computer with its perfect parallelism of computations. Looks like Argon2 fails to deliver protection against quantum computers.

The whitepaper (Table 1) says that reducing memory for Argon2d by a mere factor of 7 requires increasing the amount of computation by 2^18, and it only gets much worse beyond that.

Best of luck with your perfect quantum computer.
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November 16, 2015, 07:14:51 PM
 #670

The whitepaper (Table 1) says that reducing memory for Argon2d by a mere factor of 7 requires increasing the amount of computation by 2^18, and it only gets much worse beyond that.

Best of luck with your perfect quantum computer.

So it requires to add 18 qubits to that perfect quantum computer, it seems?

Have you seen this pic:

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November 16, 2015, 08:51:02 PM
 #671

Two years ago I was the first German blogger that took notice of Nxt. I hope for IOTA I can also play an important role to create attention in the German speaking communities (what includes Switzerland and Austria as well).

This first post includes a lot of information from this thread also some parts of the cointelegraph interview and other sources from the web.
In addition I brought attention to Jinn and how IOTA is related to this semiconductor start up:
https://altcoinspekulant.wordpress.com/2015/11/15/iota-kryptowaehrungsrevolution-zum-internet-of-things/

Have a good start in the week!


Thanks a lot !

Of course David. It would be great if I could contact you as well for an interview, not right now but begin of December, when we get closer to the ICO date. Just 4-5 questions.
Many thanks in advance!

Altcoinspekulant: Deutscher Altcoinblog.
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November 16, 2015, 09:01:57 PM
 #672

The whitepaper (Table 1) says that reducing memory for Argon2d by a mere factor of 7 requires increasing the amount of computation by 2^18, and it only gets much worse beyond that.

Best of luck with your perfect quantum computer.

So it requires to add 18 qubits to that perfect quantum computer, it seems?

You are rather confused about the abilities of quantum computers.
A 2^18 increase in sequential computation is also a 2^18 increase in quantum runtime.
Please read http://www.cs.virginia.edu/~robins/The_Limits_of_Quantum_Computers.pdf
to understand what quantum computers can and cannot do.

Scott also writes regularly about DWave and their snake-oil version of quantum computer that your pictures alludes to. See http://www.scottaaronson.com/blog/?p=2448
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November 16, 2015, 09:11:47 PM
 #673

You are rather confused about the abilities of quantum computers.
A 2^18 increase in sequential computation is also a 2^18 increase in quantum runtime.
Please read http://www.cs.virginia.edu/~robins/The_Limits_of_Quantum_Computers.pdf
to understand what quantum computers can and cannot do.

Scott also writes regularly about DWave and their snake-oil version of quantum computer that your pictures alludes to. See http://www.scottaaronson.com/blog/?p=2448

DWave is not a quantum computer, that's true.

Regarding that 2^18 issue, your paper says:
Quote
A small number of particles in superposition
states can carry an enormous amount of information:
a mere 1,000 particles can be in a superposition
that represents every number from 1 to
2^1,000 (about 10^300), and a quantum computer
would manipulate all those numbers in
parallel, for instance, by hitting the particles
with laser pulses.
While it's obvious that 1 number is not enough for Argon2 computation, if we assume that 10 numbers is enough then 18*10 extra qubits should solve the problem. Right?
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November 16, 2015, 09:36:40 PM
 #674


Scott also writes regularly about DWave and their snake-oil version of quantum computer that your pictures alludes to. See http://www.scottaaronson.com/blog/?p=2448


Scott Aaronson is a champion of scalable quantum computers: http://spectrum.ieee.org/tech-talk/computing/hardware/why-im-wagering-100000-on-quantum-computing

No sure why you bring up D-Wave, everyone knows that they are doing quantum annealing, not proper quantum computations. None of this suggests we should not take a physical theory seriously. That's what this really boils down to, engineering challenges, the theory of quantum mechanics is crystal clear on this topic.

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November 16, 2015, 09:42:05 PM
 #675

An idea has come to my mind. We could use a quantum computer to check SHA256 digests for different patterns by using Kuperberg's quantum sieve algorithm, this would let us to assess how secure SHA256 is. No patterns = hash function is close to random oracle. We could do the same for any algorithm even if it requires petabytes of RAM, we need only digests.
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November 17, 2015, 04:20:16 AM
 #676

What algorithm will IOTA use, can I mine it?

INVALID BBCODE: close of unopened tag in table (1)
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November 17, 2015, 08:29:52 AM
 #677

What algorithm will IOTA use, can I mine it?

Iota is not mineable.
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November 17, 2015, 01:38:46 PM
 #678

I wrote a comprehensive article about IOTA usage and how it fits into the IoT ecosystem:

https://medium.com/@DavidSonstebo/iota-97592581f985

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November 17, 2015, 02:02:28 PM
 #679

I've been wondering when this would be addressed. Applicable QC is alot closer than people realize.

Sergue, have you ever worked on engineering bio-weapons?

Also I don't quite see the rational for the need to create a completely different method as opposed to changing to a QC resistant algorithm such as polynomial.

https://en.wikipedia.org/wiki/Post-quantum_cryptography
http://csrc.nist.gov/groups/SMA/ispab/documents/minutes/2015-06/ispab_june-11_quantum_lchen.pdf
https://www.cs.elte.hu/blobs/diplomamunkak/msc_mat/2012/nemes_antal.pdf

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November 17, 2015, 02:31:14 PM
 #680

I've been wondering when this would be addressed. Applicable QC is alot closer than people realize.

Sergue, have you ever worked on engineering bio-weapons?

Also I don't quite see the rational for the need to create a completely different method as opposed to changing to a QC resistant algorithm such as polynomial.

https://en.wikipedia.org/wiki/Post-quantum_cryptography
http://csrc.nist.gov/groups/SMA/ispab/documents/minutes/2015-06/ispab_june-11_quantum_lchen.pdf
https://www.cs.elte.hu/blobs/diplomamunkak/msc_mat/2012/nemes_antal.pdf

Could you rephrase the question?

Are you wondering why we did the Tangle instead of Blockchain?

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