signing RPMs without a passphrase?

[Lev Lvovsky <lists2 sonous com>]

Is it possible to sign an RPM without being asked the passphrase for  
the signing key?  It hampers automated RPM creation to be asked for  
the passphrase when building them.  Otherwise, is the only other  
option just batch signing the RPMs after they've been created?

thanks,
-lev