Exponentiation by squaring
Exponentiating by squaring is an algorithm. It is used for quickly working out large integer powers of a number. It is also known as the square-and-multiply algorithm or binary exponentiation. It uses the binary expansion of the exponent. It is of quite general use, for example in modular arithmetic.
This algorithm is much faster than the ordinary method to compute such a value. Multiplying x by itself, n operations are needed to calculate x n. With the method shown above, only log2(n) operations are needed.