Patent ID: 8050403

Claim:
A method, for being performed by a computer system, of publishing a public key Q for an Elliptic Curve Cryptosystem given a private key k, a base point P and a window size w, said method for countering power analysis attacks, said method comprising: defining a table of odd multiples of said base point; shifting said private key right to create a shifted private key; translating said shifted private key to a base 2 w , thereby forming a translated, shifted key; determining, based on said translated, shifted key and said table, an initial value for a scalar multiplication of said private key k and said base point P; determining, based on said translated, shifted key and said table, a final value for said scalar multiplication, said determining said final value including: determining that said private key k is even; and upon determining that said private key k is even, subtracting said base point P from said final value; and publishing said final value for said scalar multiplication as said public key.