How to explain crypto?

[declan@well.com (Declan McCullagh)]

Brock, the crypto-challenged, humbly apologizes for his gaffe. He was
looking for a way to draw an understandable comparison of how much harder a
1024-bit implementation of RSA is to break than what current export
controls allow.

He's asking for suggestions on how in future articles he could word this so
a layman could understand it... Preferably something that could be said in
a few sentences. (Brock cops to the fact that it does an incredible
disservice to a complex topic. Remember, tho, he writes for a broad
audience with a way diverse range of understanding -- or misunderstanding,
as the case may be!)

For example, someone sent me this explanation:

  "The 1024 bit key is likely an RSA key, and is not comperable to a 40 bit
  symetric key.  From memory, 1024 bit RSA is about as hard to crack as 90
  bit symetric."

Is this a reasonable comparison?

-Declan