powmod.js

// Efficient modular exponentiation using BigInts
// Based on pseudocode from https://en.wikipedia.org/wiki/Modular_exponentiation
// !! NEVER use this method for actual cryptographic applications !!
const powMod = (base, exponent, modulus) => {

	if(modulus == 1n) {
		return 0n;
	}

	let result = 1n;
	base = base % modulus;
	while(exponent > 0n) {
		if(exponent % 2n == 1n) {
			result = (result * base) % modulus;
		}
		exponent >>= 1n;
		base = (base * base) % modulus;
	}
	
	return result;

};