G'day, GIANT SNAKEOIL SLICK THREATENS COAST OF FIREWALLS LIST Authorities Blame the NSA Good evening, viewers... In light of the many _many_ odd views that have recently been espoused in the name of cryptography, I am forced to (yet again) pretend to know something about this field. In no order: [Larry Paul] >Wouldn't 4 kb take a gazillion years to decrypt? Yes, assuming that the algorithm is 'strong'. Put it this way - keylength is one part of a large number of factors that affects the strength of a cipher. A cipher with a 4kb key could be anywhere from impossible to decrypt (<4kb message encrypted with 4kb truerandom OTP) to amazingly easy (XOR with a 4kb block). For a real algorithm, though, 4kb is way off the scale in terms of security for a symmetric cipher. That's where we start saying things like "even if every atom in the universe were actually a supercomputer then it would still not be done before heat death". [Also Larry] > Is it true that as the key expands bit-wise, the factoring time increases at > a non-linear rate? Yes. It's exponential time. In other words, it's about twice as hard to factor a 513 bit number as a 512 bit one. [Fred Avolio] >But it would be very, very, *very* secure. And would undoubtedly NOT make the system it was used in secure. This is not really aimed at Fred, since he knows this, but it's really important to remember that strong crypto is NOT NOT NOT NOT NOT a panacea. Just because you have amazing crypto doesn't mean your data isn't at risk. Cryptographic systems are hard and people make mistakes all the time. The actual cipher is rarely the bit that falls over. [Renee Lee] > Not quite, With the availability of Massively Parallel Processors capable of > Gig-instructions > per second you could find the key in a shorter time than you may think. No. You couldn't. Brute forcing a 4kb key is not possible without a trapdoor or flaw in the algorithm. IOW - even taking factoring as an example... Quantum computing may become real. This effectively square roots the complexity of an arbitrary calculation. That makes a 4096 bit number as hard to factor as a 2048 bit one. Big deal. 2048 bits is well outside the realms of possibility with an amazing new algorithm for factoring. More in part 2.... -- Ben Nagy Marconi Services Network Integration Specialist Mb: +61 414 411 520 PGP Key ID: 0x1A86E304 - [To unsubscribe, send mail to [EMAIL PROTECTED] with "unsubscribe firewalls" in the body of the message.]
