trap door

( n.)

   (alt.: trapdoor)

   1. Syn. {back door} -- a {Bad Thing}.

   2.  [techspeak]  A trap-door function is one which is easy to compute
   but  very  difficult  to  compute  the inverse of. Such functions are
   {Good   Thing}s   with   important   applications   in  cryptography,
   specifically in the construction of public-key cryptosystems.

[glossary]
[Reference(s) to this entry by made by: {back door}{patch}]