I believe you are incorrect in this statement. It is a matter of public record that RSA Security's DES Challenge II was broken in 72 hours by $250,000 worth of semi-custom machine, for the sake of solidity let's assume they used 2^55 work to break it. Now moving to a completely custom design, bumping up the cost to $500,000, and moving forward 7 years, delivers ~2^70 work in 72 hours (give or take a couple orders of magnitude). This puts the 2^69 work well within the realm of realizable breaks, assuming your attackers are smallish businesses, and if your attackers are large businesses with substantial resources the break can be assumed in minutes if not seconds.
2^69 is completely breakable. Joe Its fine assuming that moore's law will hold forever, but without
Actually, the final challenge was solved in 23 hours, about 1/3 Deep Crack, and 2/3 Distributed.net. They were lucky, finding the key after only 24% of the keyspace had been searched. More recently, RC5-64 was solved about a year ago. It took d.net 4 *years*. 2^69 remains non-trivial. Peter -----Original Message----- From: owner-cypherpunks@minder.net on behalf of Dave Howe Sent: Thu 2/17/2005 5:49 AM To: Cypherpunks; Cryptography Subject: Re: SHA1 broken? Joseph Ashwood wrote: that you can't really extrapolate a future tech curve. with *todays* technology, you would have to spend an appreciable fraction of the national budget to get a one-per-year "break", not that anything that has been hashed with sha-1 can be considered breakable (but that would allow you to (for example) forge a digital signature given an example) This of course assumes that the "break" doesn't match the criteria from the previous breaks by the same team - ie, that you *can* create a collision, but you have little or no control over the plaintext for the colliding elements - there is no way to know as the paper hasn't been published yet.