Exponentiation is a heavily used operation in public key cryptography. Which of the following options is the tightest upper bound on the number of multiplications required to compute b^n mod m,0<=b,n<=m?
a)O(log n)
b)O(sqrt(n))
c)O(n/log n)
d)O(n)
please explain..
bnmodm,0≤b,n≤mbnmodm,0≤b,n≤m ?