Quote from: Some Mouse on July 16, 2010, 12:13:52 AM

Quote from: knightmb on July 15, 2010, 11:42:49 PM

For the same reason they didn't use SHA1024 or SHA2048 or SHA4048 or SHA1000000000000000000000000000000000

No. SHA512 and Whirlpool exist, are well defined, well supported, well analyzed, and they exist for a reason.

I'm sure the same was said back when 40, 64, 128, and 256 bit encryption was coming out. SHA512 is part of SHA2, I remember when everyone was talking about how insecure SHA1 was with that significant *flaw* and how we all need to move to SHA2 because it was well defined, well supported, and well analyzed; sound familiar?

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There are lots of theoretical attacks that can be done against it, but if a program or new math proof can half the amount of time it takes to crack it,

Reversible computing techniques 'cheat' around the entropy limit. This means they can reach effective speeds far, far beyond what are possible with current computers, as they are effectively capable of performing nondeterministic operations.

You are basically betting the entire economy (if you believe bitcoins will succeed anyway) on no one developing a means to halve the effective bit length as has been done with e.g. AES.

It's careless.

I'm not betting anything for the simple fact that unless you can see into the future, we work with what we have in front of us. We can debate all day that in the future computers will be a million times faster or that some math genius is going to discover a flaw in the system that would bring everything down. I'm well aware of many peer reviewed papers and tech journals, even blogs about encryption. Not everything in existence, as I don't have the time for all of it, but enough practical experience to be able to visualize what it would really take to do what you propose.

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are we really worried about the encryption taking 100 billion years to crack but now with this new attack (insert math,attack,flaw) it's only going to take only 1 billion years to crack? How about a million years? Even one-hundred thousand years?

Ten years, assuming only minor flaws in SHA256.

If there is a major flaw (again, see the push for SHA-3) there is a much more serious problem. There does not appear to be a clear mechanism for handling a compromise of the basic algorithm, and there should be.

10 years is a good a guess as my 1 million years. SHA1 still has not been broken, but you can brute force/exploit flaws on a super-computer in under 60 hours if you have $35 million to throw at it.

Overall, I hear what you say and if BitCoin jumped in the SHA3 realm, I would sleep just as well at night as I did with it using the older SHA2 realm of technology.

I'm not trying to nitpick your post, just offering up my opinion and I certainly respect yours. I think we can both agree that if the encryption is bumped up another notch in the future, it would be a good thing for the system and community as a whole.