600 lines
12 KiB
JavaScript
600 lines
12 KiB
JavaScript
'use strict';
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Object.defineProperty(exports, '__esModule', { value: true });
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/**
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* Absolute value. abs(a)==a if a>=0. abs(a)==-a if a<0
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*
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* @param {number|bigint} a
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*
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* @returns {bigint} the absolute value of a
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*/
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const abs = function (a) {
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a = BigInt(a);
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return (a >= BigInt(0)) ? a : -a;
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};
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/**
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* Greatest-common divisor of two integers based on the iterative binary algorithm.
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*
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* @param {number|bigint} a
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* @param {number|bigint} b
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*
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* @returns {bigint} The greatest common divisor of a and b
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*/
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const gcd = function (a, b) {
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a = abs(a);
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b = abs(b);
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let shift = BigInt(0);
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while (!((a | b) & BigInt(1))) {
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a >>= BigInt(1);
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b >>= BigInt(1);
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shift++;
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}
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while (!(a & BigInt(1))) a >>= BigInt(1);
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do {
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while (!(b & BigInt(1))) b >>= BigInt(1);
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if (a > b) {
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let x = a;
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a = b;
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b = x;
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}
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b -= a;
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} while (b);
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// rescale
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return a << shift;
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};
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/**
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* The least common multiple computed as abs(a*b)/gcd(a,b)
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* @param {number|bigint} a
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* @param {number|bigint} b
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*
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* @returns {bigint} The least common multiple of a and b
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*/
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const lcm = function (a, b) {
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a = BigInt(a);
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b = BigInt(b);
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return abs(a * b) / gcd(a, b);
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};
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/**
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* Finds the smallest positive element that is congruent to a in modulo n
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* @param {number|bigint} a An integer
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* @param {number|bigint} n The modulo
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*
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* @returns {bigint} The smallest positive representation of a in modulo n
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*/
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const toZn = function (a, n) {
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n = BigInt(n);
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a = BigInt(a) % n;
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return (a < 0) ? a + n : a;
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};
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/**
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* @typedef {Object} egcdReturn A triple (g, x, y), such that ax + by = g = gcd(a, b).
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* @property {bigint} g
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* @property {bigint} x
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* @property {bigint} y
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*/
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/**
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* An iterative implementation of the extended euclidean algorithm or extended greatest common divisor algorithm.
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* Take positive integers a, b as input, and return a triple (g, x, y), such that ax + by = g = gcd(a, b).
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*
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* @param {number|bigint} a
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* @param {number|bigint} b
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*
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* @returns {egcdReturn}
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*/
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const eGcd = function (a, b) {
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a = BigInt(a);
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b = BigInt(b);
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let x = BigInt(0);
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let y = BigInt(1);
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let u = BigInt(1);
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let v = BigInt(0);
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while (a !== BigInt(0)) {
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let q = b / a;
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let r = b % a;
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let m = x - (u * q);
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let n = y - (v * q);
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b = a;
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a = r;
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x = u;
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y = v;
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u = m;
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v = n;
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}
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return {
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b: b,
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x: x,
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y: y
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};
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};
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/**
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* Modular inverse.
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*
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* @param {number|bigint} a The number to find an inverse for
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* @param {number|bigint} n The modulo
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*
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* @returns {bigint} the inverse modulo n
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*/
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const modInv = function (a, n) {
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let egcd = eGcd(a, n);
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if (egcd.b !== BigInt(1)) {
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return null; // modular inverse does not exist
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} else {
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return toZn(egcd.x, n);
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}
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};
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/**
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* Modular exponentiation a**b mod n
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* @param {number|bigint} a base
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* @param {number|bigint} b exponent
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* @param {number|bigint} n modulo
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*
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* @returns {bigint} a**b mod n
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*/
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const modPow = function (a, b, n) {
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// See Knuth, volume 2, section 4.6.3.
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n = BigInt(n);
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a = toZn(a, n);
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b = BigInt(b);
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if (b < BigInt(0)) {
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return modInv(modPow(a, abs(b), n), n);
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}
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let result = BigInt(1);
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let x = a;
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while (b > 0) {
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var leastSignificantBit = b % BigInt(2);
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b = b / BigInt(2);
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if (leastSignificantBit == BigInt(1)) {
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result = result * x;
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result = result % n;
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}
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x = x * x;
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x = x % n;
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}
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return result;
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};
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/**
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* Secure random bytes for both node and browsers. Browser implementation uses WebWorkers in order to not lock the main process
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*
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* @param {number} byteLength The desired number of random bytes
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* @param {boolean} forceLength If we want to force the output to have a bit length of 8*byteLength. It basically forces the msb to be 1
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*
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* @returns {Promise} A promise that resolves to a Buffer/UInt8Array filled with cryptographically secure random bytes
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*/
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const randBytes = async function (byteLength, forceLength = false) {
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return new Promise((resolve) => {
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let buf;
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{ // node
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const crypto = require('crypto');
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buf = Buffer.alloc(byteLength);
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crypto.randomFill(buf, (err, buf) => {
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// If fixed length is required we put the first bit to 1 -> to get the necessary bitLength
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if (forceLength)
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buf[0] = buf[0] | 128;
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resolve(buf);
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});
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}
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});
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};
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/**
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* Returns a cryptographically secure random integer between [min,max]
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* @param {bigint} max Returned value will be <= max
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* @param {bigint} min Returned value will be >= min
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*
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* @returns {Promise} A promise that resolves to a cryptographically secure random bigint between [min,max]
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*/
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const randBetween = async function (max, min = 1) {
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let bitLen = bitLength(max);
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let byteLength = bitLen >> 3;
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let remaining = bitLen - (byteLength * 8);
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let extraBits;
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if (remaining > 0) {
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byteLength++;
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extraBits = 2 ** remaining - 1;
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}
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let rnd;
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do {
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let buf = await randBytes(byteLength);
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// remove extra bits
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if (remaining > 0)
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buf[0] = buf[0] & extraBits;
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rnd = fromBuffer(buf);
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} while (rnd > max || rnd < min);
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return rnd;
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};
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/**
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* The test first tries if any of the first 250 small primes are a factor of the input number and then passes several iterations of Miller-Rabin Probabilistic Primality Test (FIPS 186-4 C.3.1)
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*
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* @param {bigint} w An integer to be tested for primality
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* @param {number} iterations The number of iterations for the primality test. The value shall be consistent with Table C.1, C.2 or C.3
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*
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* @return {Promise} A promise that resolve to a boolean that is either true (a probably prime number) or false (definitely composite)
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*/
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const isProbablyPrime = async function (w, iterations = 16) {
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/*
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PREFILTERING. Even values but 2 are not primes, so don't test.
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1 is not a prime and the M-R algorithm needs w>1.
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*/
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if (w === BigInt(2))
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return true;
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else if ((w & BigInt(1)) === BigInt(0) || w === BigInt(1))
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return false;
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/*
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Test if any of the first 250 small primes are a factor of w. 2 is not tested because it was already tested above.
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*/
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const firstPrimes = [
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3,
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5,
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7,
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11,
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13,
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17,
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19,
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23,
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29,
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31,
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37,
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41,
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43,
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47,
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53,
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59,
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61,
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67,
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71,
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73,
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79,
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83,
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89,
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97,
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101,
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103,
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107,
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109,
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113,
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127,
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131,
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137,
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139,
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149,
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151,
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157,
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163,
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167,
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173,
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179,
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181,
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191,
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193,
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197,
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199,
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211,
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223,
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227,
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229,
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233,
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239,
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241,
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251,
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257,
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263,
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269,
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271,
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277,
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281,
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283,
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293,
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307,
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311,
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313,
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317,
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331,
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337,
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347,
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349,
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353,
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359,
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367,
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373,
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379,
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383,
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389,
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397,
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401,
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409,
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419,
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421,
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431,
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433,
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439,
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443,
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449,
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457,
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461,
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463,
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467,
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479,
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487,
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491,
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499,
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503,
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509,
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521,
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523,
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541,
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547,
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557,
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563,
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569,
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571,
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577,
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587,
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593,
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599,
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601,
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607,
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613,
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617,
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619,
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631,
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641,
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643,
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647,
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653,
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659,
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661,
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673,
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677,
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683,
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691,
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701,
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709,
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719,
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727,
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733,
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739,
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743,
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751,
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757,
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761,
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769,
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773,
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787,
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797,
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809,
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811,
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821,
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823,
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827,
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829,
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839,
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853,
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857,
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859,
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863,
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877,
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881,
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883,
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887,
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907,
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911,
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919,
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929,
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937,
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941,
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947,
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953,
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967,
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971,
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977,
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983,
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991,
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997,
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1009,
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1013,
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1019,
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1021,
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1031,
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1033,
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1039,
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1049,
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1051,
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1061,
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1063,
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1069,
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1087,
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1091,
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1093,
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1097,
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1103,
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1109,
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1117,
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1123,
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1129,
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1151,
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1153,
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1163,
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1171,
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1181,
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1187,
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1193,
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1201,
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1213,
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1217,
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1223,
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1229,
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1231,
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1237,
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1249,
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1259,
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1277,
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1279,
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1283,
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1289,
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1291,
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1297,
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1301,
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1303,
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1307,
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1319,
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1321,
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1327,
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1361,
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1367,
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1373,
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1381,
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1399,
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1409,
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1423,
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1427,
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1429,
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1433,
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1439,
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1447,
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1451,
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1453,
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1459,
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1471,
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1481,
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1483,
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1487,
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1489,
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1493,
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1499,
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1511,
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1523,
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1531,
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1543,
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1549,
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1553,
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1559,
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1567,
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1571,
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1579,
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1583,
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1597,
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];
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for (let i = 0; i < firstPrimes.length && (BigInt(firstPrimes[i]) <= w); i++) {
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const p = BigInt(firstPrimes[i]);
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if (w === p)
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return true;
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else if (w % p === BigInt(0))
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return false;
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}
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/*
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1. Let a be the largest integer such that 2**a divides w−1.
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2. m = (w−1) / 2**a.
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3. wlen = len (w).
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4. For i = 1 to iterations do
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4.1 Obtain a string b of wlen bits from an RBG.
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Comment: Ensure that 1 < b < w−1.
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4.2 If ((b ≤ 1) or (b ≥ w−1)), then go to step 4.1.
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4.3 z = b**m mod w.
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4.4 If ((z = 1) or (z = w − 1)), then go to step 4.7.
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4.5 For j = 1 to a − 1 do.
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4.5.1 z = z**2 mod w.
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4.5.2 If (z = w−1), then go to step 4.7.
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4.5.3 If (z = 1), then go to step 4.6.
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4.6 Return COMPOSITE.
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4.7 Continue.
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Comment: Increment i for the do-loop in step 4.
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5. Return PROBABLY PRIME.
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*/
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let a = BigInt(0), d = w - BigInt(1);
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while (d % BigInt(2) === BigInt(0)) {
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d /= BigInt(2);
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++a;
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}
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let m = (w - BigInt(1)) / (BigInt(2) ** a);
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loop: do {
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let b = await randBetween(w - BigInt(1), 2);
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let z = modPow(b, m, w);
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if (z === BigInt(1) || z === w - BigInt(1))
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continue;
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for (let j = 1; j < a; j++) {
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z = modPow(z, BigInt(2), w);
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if (z === w - BigInt(1))
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continue loop;
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if (z === BigInt(1))
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break;
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}
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return false;
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} while (--iterations);
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return true;
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};
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/**
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* A probably-prime (Miller-Rabin), cryptographically-secure, random-number generator
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*
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* @param {number} bitLength The required bit length for the generated prime
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* @param {number} iterations The number of iterations for the Miller-Rabin Probabilistic Primality Test
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*
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* @returns {Promise} A promise that resolves to a bigint probable prime of bitLength bits
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*/
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const prime = async function (bitLength, iterations = 16) {
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return new Promise(async (resolve) => {
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{
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let rnd = BigInt(0);
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do {
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rnd = fromBuffer(await randBytes(bitLength / 8, true));
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} while (! await isProbablyPrime(rnd, iterations));
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resolve(rnd);
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}
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});
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};
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/* HELPER FUNCTIONS */
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function fromBuffer(buf) {
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let ret = BigInt(0);
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for (let i of buf.values()) {
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let bi = BigInt(i);
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ret = (ret << BigInt(8)) + bi;
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}
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return ret;
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}
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function bitLength(a) {
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let bits = 1;
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do {
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bits++;
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} while ((a >>= BigInt(1)) > BigInt(1));
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return bits;
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}
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exports.abs = abs;
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exports.eGcd = eGcd;
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exports.gcd = gcd;
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exports.isProbablyPrime = isProbablyPrime;
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exports.lcm = lcm;
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exports.modInv = modInv;
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exports.modPow = modPow;
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exports.prime = prime;
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exports.randBetween = randBetween;
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exports.randBytes = randBytes;
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exports.toZn = toZn;
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