[Tarang]

The hashes that come out of bitcoin mining aren't just any ordinary hash you could use to crack passwords, though. The hashes have to begin with a number of 0s corresponding to the difficulty.

Most password hashes (including the salt) hardly have these 0s so even as a lookup table the blockchain isn't very good.

[drakaal]

You don't attack Sha with the miner, you generate prime factors. Those can then be used to attack any encryption.

Not convinced this is what is being done. Just saying it doesn't matter about the salt for this to be worth while.

[gibybo]

SHA has nothing to do with prime numbers. Bitcoin also has nothing to do with prime numbers.

Further, prime numbers are only useful in a very specific case of cryptography, nowhere near 'all encryption'.

[drakaal]

Nothing to do with prime numbers?

http://www.femto-second.com/papers/SHA256LimitedStatisticalA...

http://www.ietf.org/rfc/rfc4634.txt

http://eprint.iacr.org/2010/548.pdf

http://eprint.iacr.org/2010/548.pdf

[gibybo]

Yes, nothing to do with prime numbers. SHA-2 uses some constants. A lot of cryptography needs constants for various reasons. There is always some concern that the creator chose specific constants that weaken or give them a backdoor to the crypto scheme. To reduce this concern, they often choose constants from some simple mathematical basis, perhaps the numbers '1234567890', or digits of pi, etc. In SHA-2's case, they used the first 32 bits of the fractional parts of the square roots of the first n primes.

The numbers they use are not primes, nor are primes useful in any way for attacking SHA. The algorithm still has nothing to do with prime numbers.