hi, if gcd(a,m)=1, for a*a inverse==1 mod m is it better to find a invese=a^(m-2) mod m by binary exponentiation modulo m or is it more time efficient by extended euclids algorithm for large 'm'? thanks. Sarath. __________________________________ Do you Yahoo!? Yahoo! Mail - More reliable, more storage, less spam http://mail.yahoo.com