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Author Topic: Could bitcoin eventually crack SHA256?  (Read 10913 times)
gigabytecoin
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May 09, 2011, 11:37:54 PM
 #1

I imagine that once the difficulty gets so high that you're successful hashes start looking like this 000000000000000000000000000000fa that somebody might be able to break SHA256 would they not? Eventually we would find two hash values that were the same but had different inputs. That or Bitcoin would cease to work, right?

At what level of difficulty will we have to change our cryptographic hash function? (When will we have to re-inforce our security?)
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eMansipater
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May 09, 2011, 11:50:51 PM
 #2

I imagine that once the difficulty gets so high that you're successful hashes start looking like this 000000000000000000000000000000fa that somebody might be able to break SHA256 would they not? Eventually we would find two hash values that were the same but had different inputs. That or Bitcoin would cease to work, right?

At what level of difficulty will we have to change our cryptographic hash function? (When will we have to re-inforce our security?)
To get difficulty high enough that successful hashes need to start with that many zeroes would take more computing power than you can conceivably imagine.  Which is the understatement of the century.   Reaching maximum difficulty would require a sustained rate of approximately 7*2^224 Mhash.

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May 09, 2011, 11:57:11 PM
 #3

The difficulty ever getting that high is very unlikely.

Difficulty does not necessarily constantly increase without an increase in total hash rate to cause it.

Even if you gave everyone in the world hashing power equal to the current network total, the difficulty would "only" be 1,800,000,000,000.

if i am doing my numbers right, that corresponds to a target of roughly 6,582,018,229,284,824,168,619,876,730,229,402,019,930,943,462,534,319,453,394,436,096

not sure what that is in hex, as i cannot find a decimal to hex converter that will handle that many digits, but it is still waaaay above a target that is likely to result in the finding of collisions.
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May 10, 2011, 12:13:45 AM
 #4

Thank you for putting my mind at ease both of you!
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May 10, 2011, 01:13:30 AM
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The difficulty ever getting that high is very unlikely.

Difficulty does not necessarily constantly increase without an increase in total hash rate to cause it.

Even if you gave everyone in the world hashing power equal to the current network total, the difficulty would "only" be 1,800,000,000,000.

if i am doing my numbers right, that corresponds to a target of roughly 6,582,018,229,284,824,168,619,876,730,229,402,019,930,943,462,534,319,453,394,436,096

not sure what that is in hex, as i cannot find a decimal to hex converter that will handle that many digits, but it is still waaaay above a target that is likely to result in the finding of collisions.

6582018229284824168619876730229402019930943462534319453394436096 dec = 100000000000000000000000000000000000000000000000000000 hex Smiley

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May 10, 2011, 07:08:01 AM
 #6

Thank you for putting my mind at ease both of you!
You're more than welcome!

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May 10, 2011, 07:41:06 AM
 #7

i cannot find a decimal to hex converter that will handle that many digits

Code:
$ python3
>>> hex(6582018229284824168619876730229402019930943462534319453394436096)
'0x100000000000000000000000000000000000000000000000000000'
>>>
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May 10, 2011, 08:47:25 AM
 #8

We should be safe... unless somebody has a secret quantum computer!  Shocked

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July 05, 2012, 03:50:33 PM
 #9

No the concern is still valid.

Computer power will continue to double every year or two. The exponential effect will catch up with almost any algorithm much sooner than we expect.

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July 05, 2012, 03:53:37 PM
 #10

No the concern is still valid.

Computer power will continue to double every year or two. The exponential effect will catch up with almost any algorithm much sooner than we expect.
Not valid, if you only consider Moore's law. Even with an exponential increase in hashing speeds, it is still unbreakable for many centuries and beyond. The worry is whether a protocol flaw can be found to reduce the amount of calculations needed to accelerate hashing speeds.

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July 05, 2012, 04:06:17 PM
 #11

No the concern is still valid.

Not really.  Imagine you built a perfect computer; forget about GHash and Megaherts.  You built a computer which used the absolute minimum amount of energy theoretically possible to record a change in a single bit (1 to 0 or 0 to 1).  We are talking about the limits of thermodynamics; nothing more efficient is even possible.  Now imagine you used most of the natural resources in our star system to construct a dyson sphere and covered the entire surface of this sphere with a single star system sized super computer.  Now imagine you could keep this supercomputer cooled at roughly absolute zero and could do so without expending any additional energy.

If you had that and captured (with no inefficiency or loss) the entire energy output of our star (not just in a day or week but continually until it burned out) you couldn't COUNT to 2^256 before you ran out of energy.   Keep in mind this is simply counting.  Just counting, not hashing, not comparing, not performing lookups just counting 1 .. 2 .. 3 .. .... 2^256-1.

This program couldn't finish even using all the energy in our star system
Code:
Int256 i = 0;

while (i < Int256.Max)
{
    i++
}
Print("Congrats we counted to 2^256")


Or put another way:

Quote
These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space.

http://www.schneier.com/blog/archives/2009/09/the_doghouse_cr.html
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July 05, 2012, 04:18:18 PM
 #12

Or put another way:

Quote
These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space.

http://www.schneier.com/blog/archives/2009/09/the_doghouse_cr.html

Quote
until computers are built from something other than matter and occupy something other than space

Quote
until computers are built from something other than matter and occupy something other than space

foggyb
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July 06, 2012, 12:46:31 AM
 #13


Computer power will continue to double every year or two.

You know what they say about laws...........
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July 06, 2012, 03:16:39 AM
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Today I will fuck mess with them Bitcoiners.
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August 21, 2012, 04:03:52 AM
 #15

So brute-forcing pirate's wallet would take a really long time?  Wink

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August 21, 2012, 04:05:50 AM
 #16

It couldn't crack SHA256, that would take precious cycles away from mining.

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August 21, 2012, 04:44:30 AM
 #17

Or put another way:

Quote
These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space.

http://www.schneier.com/blog/archives/2009/09/the_doghouse_cr.html

Quote
until computers are built from something other than matter and occupy something other than space

Quote
until computers are built from something other than matter and occupy something other than space



well, if you believe him then you should become a bull like your avatar.  Cheesy
markm
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August 21, 2012, 06:52:50 AM
 #18

Of course its inevitable, eventually...

Have you never heard that old saying, how does it go, "eventually say eventually", or something along those lines?

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August 21, 2012, 12:41:52 PM
 #19

Or put another way:

Quote
These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space.

http://www.schneier.com/blog/archives/2009/09/the_doghouse_cr.html

Quote
until computers are built from something other than matter and occupy something other than space

Quote
until computers are built from something other than matter and occupy something other than space



well, if you believe him then you should become a bull like your avatar.  Cheesy

I am a bull.  Wink
mimarob
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August 21, 2012, 12:49:20 PM
 #20

I believe there might be an analytical crack before that happened, remember MD5 was broken by a clever algorithm in 2006 but is still unavailable for brute-force attacks.


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