Japanese researchers break 41 out of 64 steps of SHA256 with preimage attack.

empoweoqwj

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Quote from: pungopete468 on December 19, 2013, 10:19:10 PM

Quote from: empoweoqwj on December 19, 2013, 09:50:50 PM

Quote from: pungopete468 on December 19, 2013, 03:16:13 PM

Without quantum computing a 51% attack will never work.

After quantum computing becomes mainstream, then even a 51% attack by means of quantum computing will be unrealistic...

I don't think this type of attack is going to happen... Ever.

Bitcoin will probably be replaced by something else by the time "quantum computing goes mainstream".

I don't think BitCoin can be replaced in the common sense of the word. BitCoin may not be the most popular option to trade with at a given time, but unless the internet is wiped out completely it will remain trading on some market somewhere and will always serve some purpose.

It could be replaced by something better, or just wiped out by concerted government action. Who knows. Not saying it will be, but in the time it takes quantum computing to go mainstream, we will probably have other things to worry about, like the planet dying.

pungopete468

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Quote from: empoweoqwj on December 19, 2013, 09:50:50 PM

Quote from: pungopete468 on December 19, 2013, 03:16:13 PM

Without quantum computing a 51% attack will never work.

After quantum computing becomes mainstream, then even a 51% attack by means of quantum computing will be unrealistic...

I don't think this type of attack is going to happen... Ever.

Bitcoin will probably be replaced by something else by the time "quantum computing goes mainstream".

I don't think BitCoin can be replaced in the common sense of the word. BitCoin may not be the most popular option to trade with at a given time, but unless the internet is wiped out completely it will remain trading on some market somewhere and will always serve some purpose.

empoweoqwj

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Quote from: pungopete468 on December 19, 2013, 03:16:13 PM

Without quantum computing a 51% attack will never work.

After quantum computing becomes mainstream, then even a 51% attack by means of quantum computing will be unrealistic...

I don't think this type of attack is going to happen... Ever.

Bitcoin will probably be replaced by something else by the time "quantum computing goes mainstream".

Klestin

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Activity: 493

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Quote from: DeathAndTaxes on December 17, 2013, 08:57:00 PM

You "could" if you made computers out of something other than matter and they occupied something other than space.

You do realize he was intentionally describing bitcoin mining, right?

Kazimir

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Quote from: Gabi on December 17, 2013, 09:26:46 AM

Quote

SHA3

Do you guys trust it?

Yep, I sure do. Especially because of the way it was carefully selected from a range of very well thought through alternatives, and investigated by hundreds of independent cryptography experts worldwide (and even many more after it was annoucned the official SHA3 standard).

pungopete468

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Activity: 1470

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Without quantum computing a 51% attack will never work.

After quantum computing becomes mainstream, then even a 51% attack by means of quantum computing will be unrealistic...

I don't think this type of attack is going to happen... Ever.

kuverty

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Activity: 770

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Quote from: pand70 on December 16, 2013, 09:43:55 PM

Quote from: TheoryOfBitcoin on December 16, 2013, 09:11:47 PM

Quote from: grue on December 16, 2013, 09:08:44 PM

Title: Japanese researchers break 41 out of 64 steps of SHA256 with preimage attack.
Abstract: In this paper, we propose preimage attacks [...]

sensationalist 6/10

Do you not understand all scientific papers use propose?

Propose as in "You can do it this way that we discovered"

Not propose as in "We think"

I think he means that you should evaluate the actual preimage attack that they propose before saying that they broke it.
I mean i can propose an attack: Search for all the possible keys one by one... This is a nice theoretical attack but has no value in the real world...

First time I hear exhaustive search described as a "nice theoretical attack" Grin

prezbo

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Quote from: Tirapon on December 19, 2013, 09:04:26 AM

My bad, turns out its been done already. Some guy called Satoshi already invented it back in 2008.

That idea-stealing bastard!

Tirapon

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Quote from: empoweoqwj on December 19, 2013, 04:23:21 AM

Quote from: Tirapon on December 19, 2013, 04:19:47 AM

Quote from: empoweoqwj on December 17, 2013, 09:16:40 PM

Quote from: Tirapon on December 17, 2013, 07:52:02 PM

Quote from: pand70 on December 16, 2013, 09:43:55 PM

Quote from: TheoryOfBitcoin on December 16, 2013, 09:11:47 PM

Quote from: grue on December 16, 2013, 09:08:44 PM

Title: Japanese researchers break 41 out of 64 steps of SHA256 with preimage attack.
Abstract: In this paper, we propose preimage attacks [...]

sensationalist 6/10

Do you not understand all scientific papers use propose?

Propose as in "You can do it this way that we discovered"

Not propose as in "We think"

I think he means that you should evaluate the actual preimage attack that they propose before saying that they broke it.
I mean i can propose an attack: Search for all the possible keys one by one... This is a nice theoretical attack but has no value in the real world...

You could make a start on this attack by convincing people to pool their resources, perhaps by offering a financial incentive (maybe some bitcoins for contributing computing power)? People could even work on creating some sort of application specific hardware to efficiently search for SHA-256 hash values. You could structure it so that rewards are payed out proportionally to each persons contribution.

You make this stuff up as you type right?

Pretty much, yeah. In fact this last discussion has just given me an idea for a new type of P2P payment system - One which works without the need for a central authority to keep track of the ledger...

Are you sure its new? Lots of P2P payment systems have been proposed, and then promptly disappeared .................

My bad, turns out its been done already. Some guy called Satoshi already invented it back in 2008.

empoweoqwj

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Activity: 518

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Quote from: pungopete468 on December 19, 2013, 04:51:15 AM

Quote from: empoweoqwj on December 19, 2013, 04:25:39 AM

Quote from: pungopete468 on December 19, 2013, 04:24:27 AM

BitCoin can be hacked... I saw it in the movie Transformers.

Another random post ..... this thread is increasingly full of them. That's what happens when you talk about something complicated Wink

It was intended to be comical. It's a quarter to 5 in the morning where I'm at so I really can't help myself...

The hackers will all be like "I wonder... It looks like there's some sort of message embedded within the signal..." lol

Understood. Quarter to 5 in the morning jokes are normally best kept till morning

pungopete468

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Activity: 1470

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Quote from: empoweoqwj on December 19, 2013, 04:25:39 AM

Quote from: pungopete468 on December 19, 2013, 04:24:27 AM

BitCoin can be hacked... I saw it in the movie Transformers.

Another random post ..... this thread is increasingly full of them. That's what happens when you talk about something complicated Wink

It was intended to be comical. It's a quarter to 5 in the morning where I'm at so I really can't help myself...

The hackers will all be like "I wonder... It looks like there's some sort of message embedded within the signal..." lol

empoweoqwj

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Activity: 518

Merit: 500

Quote from: pungopete468 on December 19, 2013, 04:24:27 AM

BitCoin can be hacked... I saw it in the movie Transformers.

Another random post ..... this thread is increasingly full of them. That's what happens when you talk about something complicated Wink

pungopete468

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Activity: 1470

Merit: 504

BitCoin can be hacked... I saw it in the movie Transformers.

empoweoqwj

hero member

Activity: 518

Merit: 500

Quote from: Tirapon on December 19, 2013, 04:19:47 AM

Quote from: empoweoqwj on December 17, 2013, 09:16:40 PM

Quote from: Tirapon on December 17, 2013, 07:52:02 PM

Quote from: pand70 on December 16, 2013, 09:43:55 PM

Quote from: TheoryOfBitcoin on December 16, 2013, 09:11:47 PM

Quote from: grue on December 16, 2013, 09:08:44 PM

Title: Japanese researchers break 41 out of 64 steps of SHA256 with preimage attack.
Abstract: In this paper, we propose preimage attacks [...]

sensationalist 6/10

Do you not understand all scientific papers use propose?

Propose as in "You can do it this way that we discovered"

Not propose as in "We think"

I think he means that you should evaluate the actual preimage attack that they propose before saying that they broke it.
I mean i can propose an attack: Search for all the possible keys one by one... This is a nice theoretical attack but has no value in the real world...

You could make a start on this attack by convincing people to pool their resources, perhaps by offering a financial incentive (maybe some bitcoins for contributing computing power)? People could even work on creating some sort of application specific hardware to efficiently search for SHA-256 hash values. You could structure it so that rewards are payed out proportionally to each persons contribution.

You make this stuff up as you type right?

Pretty much, yeah. In fact this last discussion has just given me an idea for a new type of P2P payment system - One which works without the need for a central authority to keep track of the ledger...

Are you sure its new? Lots of P2P payment systems have been proposed, and then promptly disappeared .................

Tirapon

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Activity: 898

Merit: 1000

Quote from: empoweoqwj on December 17, 2013, 09:16:40 PM

Quote from: Tirapon on December 17, 2013, 07:52:02 PM

Quote from: pand70 on December 16, 2013, 09:43:55 PM

Quote from: TheoryOfBitcoin on December 16, 2013, 09:11:47 PM

Quote from: grue on December 16, 2013, 09:08:44 PM

Title: Japanese researchers break 41 out of 64 steps of SHA256 with preimage attack.
Abstract: In this paper, we propose preimage attacks [...]

sensationalist 6/10

Do you not understand all scientific papers use propose?

Propose as in "You can do it this way that we discovered"

Not propose as in "We think"

I think he means that you should evaluate the actual preimage attack that they propose before saying that they broke it.
I mean i can propose an attack: Search for all the possible keys one by one... This is a nice theoretical attack but has no value in the real world...

You could make a start on this attack by convincing people to pool their resources, perhaps by offering a financial incentive (maybe some bitcoins for contributing computing power)? People could even work on creating some sort of application specific hardware to efficiently search for SHA-256 hash values. You could structure it so that rewards are payed out proportionally to each persons contribution.

You make this stuff up as you type right?

Pretty much, yeah. In fact this last discussion has just given me an idea for a new type of P2P payment system - One which works without the need for a central authority to keep track of the ledger...

empoweoqwj

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Activity: 518

Merit: 500

So many people on a single thread with so little knowledge of what is being talked about. Classic Wink

BitThink

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As far as I know, preimage attack is just to find a collision (given h(x) and x, find a y !=x and h(y) = h(x) ) more efficiently than brute force. However, to change block history you have to find a way to only alter a part of inputs and still maintain the same hash, that's not something preimage attack does.

greenlion

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Activity: 667

Merit: 500

Quote from: BitThink on December 18, 2013, 11:38:41 PM

Quote from: justusranvier on December 18, 2013, 11:59:34 AM

Quote from: greenlion on December 18, 2013, 05:10:38 AM

A pre-image attack that does not encompass all 64 steps just results in something indistinguishable from the empirical effect of everyone in the world being able to hash faster.

I think the second preimage attack is the one that where we should panic because that means an attacker might be able to rewrite the transaction history.

A first preimage attack just means mining got easier as you said.

No, the attacker cannot rewrite the transaction history because the following reason

support the blockchain is ..., A, B, C, ...

B includes the hash of A, and C includes the hash of B. The preimage attach you mean is to find a B' having a same hash value included in C. However, remember that B' has in the same time to satisfy a lot of constrains: it has to include hash(A), it has to have correct format, and it has to include some transactions beneficial to the attacker

Therefore, to be a successful attack, it is not enough to find a hash(B') == hash(B). You can only modify a small part of B to get a hash(B') == hash(B), that will be much much more difficult than ordinary preimage attack.

That's not what a preimage attack is.

What you're talking about is pre-mining blocks. A preimage attack has nothing to do with the relationship of blocks to each other.

A preimage attack is when something about the nature of the hash allows you to systematically reduce the search space of original pre-hashed inputs. I.e. the hash is "weak" because it tells you something about what value produced the hash.

BitThink

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Quote from: justusranvier on December 18, 2013, 11:59:34 AM

Quote from: greenlion on December 18, 2013, 05:10:38 AM

A pre-image attack that does not encompass all 64 steps just results in something indistinguishable from the empirical effect of everyone in the world being able to hash faster.

I think the second preimage attack is the one that where we should panic because that means an attacker might be able to rewrite the transaction history.

A first preimage attack just means mining got easier as you said.

No, the attacker cannot rewrite the transaction history because the following reason

support the blockchain is ..., A, B, C, ...

B includes the hash of A, and C includes the hash of B. The preimage attach you mean is to find a B' having a same hash value included in C. However, remember that B' has in the same time to satisfy a lot of constrains: it has to include hash(A), it has to have correct format, and it has to include some transactions beneficial to the attacker

Therefore, to be a successful attack, it is not enough to find a hash(B') == hash(B). You can only modify a small part of B to get a hash(B') == hash(B), that will be much much more difficult than ordinary preimage attack.

justusranvier

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Quote from: greenlion on December 18, 2013, 05:10:38 AM

A pre-image attack that does not encompass all 64 steps just results in something indistinguishable from the empirical effect of everyone in the world being able to hash faster.

I think the second preimage attack is the one that where we should panic because that means an attacker might be able to rewrite the transaction history.

A first preimage attack just means mining got easier as you said.

Topic: Japanese researchers break 41 out of 64 steps of SHA256 with preimage attack. (Read 8602 times)