METHOD AND APPARATUS FOR OPERAING ELLIPTIC CURVE SCALAR MULTIPLICATION

PURPOSE: A method and a device for an elliptic curve scalar multiplication are provided to identify a present calculating location by starting the multiplication at a random location. CONSTITUTION: A value r between a value m corresponding to a binary-bit number of 1 and secret key is randomly selected(S130). The selected value r is substituted for a variable J which is initial bit of Right-to-Left calculation(S320). The Right-to-Left calculation is repeated(S330). An equation J=m-1 is determined(S340). In order to prevent the intersection point of the Right-to-Left calculation and Left-to-Right calculation from becoming known, dummy calculation is inserted(S350). A value r-1 is substituted for the variable J which is initial bit of Left-to-Right calculation(S360). The Left-to-Right calculation is repeated(S370). An equation J=m-1 is determined(S380). [Reference numerals] (AA) Start; (BB) End; (S310) Selecting a random value r from 1 to m; (S320) Substituting J=r; (S330) Right-to-Left calculation to a J-th bit, J++; (S350) Inserting dummy calculation; (S360) Substituting J=r-1; (S370) Left-to-Right calculation to the J-th bit, J--