Function Exp

utils/big.go:212–225

Exp implements exponentiation by squaring. Exp returns a newly-allocated big integer and does not change base or exponent. The result is truncated to 256 bits. Courtesy @karalabe and @chfast.

(base, exponent *big.Int)

//
// Courtesy @karalabe and @chfast.
func Exp(base, exponent *big.Int) *big.Int {
	result := big.NewInt(1)

	for _, word := range exponent.Bits() {
		for i := 0; i < wordBits; i++ {
			if word&1 == 1 {
				U256(result.Mul(result, base))
			}
			U256(base.Mul(base, base))
			word >>= 1
		}
	}
	return result
}