Source : Free On-Line Dictionary of Computing

trap-door function
     
         A special class of {one-way
        function}, which is reversible if you know a certain secret
        associated with the function.
     
        {(http://www.rsasecurity.com/rsalabs/faq/2-3-2.html)}.
        {(http://www.ieor.berkeley.edu/~jshu/knapsack/Review/OverviewPK.html)}.
     
        (2003-05-22)