The point is that, according to the cryptographic theories in fashion when die public-key system was developed and for thirty-odd years thereafter, it was theoretically impossible to crack a public-key system within the projected life span of the universe. Theories have changed, though—they tend to do that. Today, some bright sparks claim that using Eiji recursion and other bits of black art, it's possible to crack a 70-bit code in a couple of days of churning on a fast enough computer. Which is why few people bother with anything less than an 85-bit code as of 2056. (Should the fact that Barnard plumped for a less secure system tell me something? Or was I still reaching ... ?)