In this paper we propose an efficient and secure elliptic curve scalar multiplication algorithm over odd prime fields. For this purpose, we propose an explicit algorithm for short addition-subtraction chain method which utilizes a 2's Complement with window method. We term it as W2CASC. Our proposed scalar multiplication algorithm based on W2CASC algorithm has preceded by 12.7% to 28% 160 bit multiplier over similar techniques. Hence scalar multiplication utilizing W2CASC algorithm shows significance in application to elliptic curve cryptosystems. Also our algorithm has preceded by 26% to 28% in context of Elliptic Curve Cryptosystems (ECC).