  Research in the field of electronic signature confirmation has been active
for some 20 years now. Unfortunately present certificate-based solutions also
come from that age when no-one knew about online data transmission. The
official standardized X.509 framework also depends heavily on offline
operations, one of the most complicated ones being certificate revocation
handling. This is done via huge Certificate Revocation Lists which are both
inconvenient and expencive. Several improvements to these lists are proposed
and in this report we try to analyze them briefly. We conclude that although it
is possible to do better than in the original X.509 setting, none of the
solutions presented this far is good enough.
