Bitcoin Forum

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.

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.

Thank you for putting my mind at ease both of you!

6582018229284824168619876730229402019930943462534319453394436096 dec = 100000000000000000000000000000000000000000000000000000 hex :)

You're more than welcome!

$ python3
>>> hex(6582018229284824168619876730229402019930943462534319453394436096)
'0x100000000000000000000000000000000000000000000000000000'
>>> 

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

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.

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

Or put another way:


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

You know what they say about laws...........

http://2.bp.blogspot.com/-1iUTNZ8LDIs/T7CUVM6HNzI/AAAAAAAAHIQ/2xjwXA_jI7s/s1600/godblog.jpg
Today I will fuck mess with them Bitcoiners.

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

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

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

Of course its inevitable, eventually...

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

-MarkM-

I am a bull.  ;)

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.

Maybe related:

US government developing ultimate cyber weapon; Prime-factoring quantum computing makes encryption obsolete

http://www.naturalnews.com/036878_quantum_computing_decryption_algorithms_government_secrets.html (http://www.naturalnews.com/036878_quantum_computing_decryption_algorithms_government_secrets.html)

Some day I plan on popping open one of my old math text books and running through the SHA-256 math formula and solve it for 'x'. Where 'x' is the private key of Pirate's BTC address.

Should be close to the difficulty of solving the Pythagorean theorem and such. Maybe with a few more symbols and numbers. Like E=mc^2