@techreport{TR-IC-98-39, number = {IC-98-39}, author = {Julio López and R. Dahab}, title = {Improved Algorithms for Elliptic Curve Arithmetic in {$GF(2^n)$}}, month = {October}, year = {1998}, institution = {Institute of Computing, University of Campinas}, note = {In English, 12 pages. \par\selectlanguage{english}\textbf{Abstract} This paper describes three contributions for the efficient implementation of elliptic curve cryptosystems in $GF(2^n)$. The first is a new method for doubling an elliptic curve point, which is simpler to implement than the fastest known method, due to Schroeppel, and which favors sparse elliptic curve coefficients. The second is a generalized and improved version of the Guajardo and Paar's formulas for computing repeated doubling points. The third contribution consists of a new kind of projective coordinates that provides the fastest known arithmetic on elliptic curves. The algorithms resulting from this new formulation lead to a running time improvement for computing a scalar multiplication of about $17\%$ over previous projective coordinate methods. } }