1. A method of providing a point multiple in an elliptic curve cryptosystem, said point multiple being derived from a scalar and a point on an elliptic curve having an equation of the form y 2 &plus;xy&equals;x 3 &plus;a 1 x 2 &plus;1, where al is either 0 or 1, said method comprising the steps of: a) obtaining a pair of coefficients derived from a truncator of said elliptic curve; b) computing a representation of said scalar from said pair of coefficients, said scalar, and said truncator of said elliptic curve; c) computing said point multiple using said representation of said scalar and a Frobenius mapping &tgr;; d) providing said point multiple to said elliptic curve cryptosystem.