Ah, of course, that makes sense.
By the way, if you didn’t see it already, there’s a discussion on the security of secp256k1 on the forum:
http://www.bitcoin.org/smf/index.php?topic=2699.0
Hal (i presume this is Hal Finney) seems to think the curve is at higher risk of attack than random curves. I guess you chose secp256k1 for the mentioned performance improvement?