Prof. George Purdy's Webpage

Recent papers in the subject of Discete & Computational Geometry

• G. Purdy, J.W. Smith, .Lines, Circles, Planes and Spheres,. arxiv.org/0907.0724, to appear in Discrete and Computational Geometry, Springer Verlag, New York.
• G.Purdy, J.W.Smith, "Bichromatic and Equichromatic Lines in C2 and R2. Has appeared in the Journal Discrete and Computational Geometry, Springer Verlag, New York.

Books and Chapters in Discrete and Computational Geometry

• Paul Erdos and G.Purdy, "Extremal Problems in Combinatorial Geometry", Chapter 17 of Handbook of Combinatorics, Vol I, pp. 809-874, Edited by R.L.Graham, M.Grotschel, L.Lovasz, , North Holland, and MIT Press, 1995.

Papers in Security and Cryptography

G. Purdy, 1974 paper in The Communications of the ACM , .A High Security Login Procedure.

Abstract

The author introduces a lacunary (Purdy) polynomial P(x) of degree d ~ 10^50 modulo a prime p ~ 10^200. The original purpose of P(x) was to protect passwords on the Arpanet. ( Google .Purdy Polynomial. for description of its use in the VAX VMS system of DEC) but it has been used way beyond this, particularly in the defense industry and in (proprietary) software protection. A top secret clearance would be required to learn the details of its use in defense. Suffice it to say that its extremely high security makes it suitable for protecting the codes that are used to arm nuclear weapons in missiles and bombers.