A Mighty Number Falls

space_in_your_face writes "An international team has broken a long-standing record in an impressive feat of calculation. On March 6, computer clusters from three institutions (the EPFL, the University of Bonn, and NTT in Japan) reached the end of eleven months of strenuous calculation, churning out the prime factors of a well-known, hard-to-factor number — 2^1039 - 1 — that is 307 digits long." The lead researcher believes "the writing is on the wall" for 1024-bit encryption. "Last time, it took nine years for us to generalize from a special to a non-special hard-to factor number (155 digits). I won't make predictions, but let's just say it might be a good idea to stay tuned."

Comments

Re:How many people have the computing power ...

[Anonymous Cowpat]

governments. Who, incidentally, are the prime targets for using encryption against.

Three years isn't a whole lot.

[Kadin2048]

I understand that they'll be able to crack 1024, but still, 3 years to see my e-mails. It's not worth it for them. Now when they got it down to 3 hours I'll be worried, but by then we'll probably be using 4096.

True, but what you need to think about is forward secrecy.

There are lots of things being transmitted today that are still going to be in use three years from now. For example, think of financial information: if you use an encryption standard that's acceptable right now, but can be broken in three years (or, is trivially breakable in three years due to increases in computer power or techniques), then you're in trouble, because some of that information is still going to be sensitive/valuable in three years. The fact that you'll be using 4096 bits then doesn't matter, if someone grabs it now and crunches on it for a while. Same with identification numbers (SSNs, etc); if I grab a batch of numbers today, most of them will probably still be good in ten or fifteen years, and some of them will still be good in 30 or 40. That's how far out you need to be thinking when choosing an encryption standard for that data.

There are some things where only immediate security matters (transmitting big session keys that get thrown away a few hours or minutes later), but many other things -- and I think general file encryption falls into this category -- where it's hard to predict for how long the encrypted information might be sensitive or valuable.