Function modularExponentiation

cipher/diffiehellman/diffiehellmankeyexchange.go:28–45

r = (b^e)%mod

(b, e, mod int64)

// r = (b^e)%mod
func modularExponentiation(b, e, mod int64) int64 {

	//runs in O(log(n)) where n = e
	//uses exponentiation by squaring to speed up the process
	if mod == 1 {
		return 0
	}
	var r int64 = 1
	b = b % mod
	for e > 0 {
		if e&1 == 1 {
			r = (r * b) % mod
		}
		e = e >> 1
		b = (b * b) % mod
	}
	return r
}