the rest of the key

I was just wondering.... If the NSA could get it's hands on half (40) of any particular clipper key, wouldn't that just leave 2^40 to compute? Even with brute force, it's trivial even next to DES.

"half" is a a random number which is XOR'd with 80 bits. Both halves look random. The XOR of the two halves is not. Eric