187 lines
4.7 KiB
JavaScript
187 lines
4.7 KiB
JavaScript
import { cryptoRandom, generate_prime } from "./random_primes.js";
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import { mod_exp } from "./math.js";
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class Cyphertext {
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constructor(key, plainText, r) {
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if (r === undefined) {
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r = cryptoRandom(4096);
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// Resample to avoid modulo bias.
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while (r >= key.n) {
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r = cryptoRandom(4096);
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}
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}
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// Compute g^m by binomial theorem.
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let gm = (1n + key.n * plainText) % key.n ** 2n;
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// Compute g^m r^n from crt
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this.cyphertext = (gm * mod_exp(r, key.n, key.n ** 2n)) % key.n ** 2n;
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this.r = r;
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this.pubKey = key;
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this.plainText = plainText;
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this.readOnly = false;
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}
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update(c) {
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this.cyphertext = (this.cyphertext * c.cyphertext) % this.pubKey.n ** 2n;
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this.r = (this.r * c.r) % this.pubKey.n ** 2n;
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this.plainText += c.plainText;
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}
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toString() {
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return "0x" + this.cyphertext.toString(16);
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}
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prove() {
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return new ProofSessionProver(this);
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}
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asReadOnlyCyphertext() {
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return new ReadOnlyCyphertext(this.pubKey, this.cyphertext);
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}
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}
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class ProofSessionProver {
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constructor(cipherText) {
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this.cipherText = cipherText;
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this.rp = cryptoRandom(4096);
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while (this.rp >= this.cipherText.pubKey.n) {
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this.rp = cryptoRandom(4096);
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}
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}
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get a() {
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return mod_exp(this.rp, this.cipherText.pubKey.n, this.cipherText.pubKey.n ** 2n);
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}
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noise() {
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return mod_exp(this.rp, this.cipherText.pubKey.n, this.cipherText.pubKey.n ** 2n);
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}
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prove(challenge) {
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return (
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((this.rp % this.cipherText.pubKey.n) *
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mod_exp(this.cipherText.r, challenge, this.cipherText.pubKey.n)) %
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this.cipherText.pubKey.n
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);
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}
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asVerifier() {
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return this.cipherText
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.asReadOnlyCyphertext()
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.prove(this.cipherText.plainText, this.noise());
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}
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}
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window.Cyphertext = Cyphertext;
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export class ReadOnlyCyphertext {
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constructor(key, cyphertext) {
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this.cyphertext = cyphertext;
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this.pubKey = key;
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this.readOnly = true;
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}
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update(c) {
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this.cyphertext = (this.cyphertext * c.cyphertext) % this.pubKey.n ** 2n;
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}
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prove(plainText, a) {
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return new ProofSessionVerifier(this, plainText, a);
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}
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}
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class ProofSessionVerifier {
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constructor(cipherText, plainText, a) {
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this.cipherText = cipherText;
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this.cipherText.update(this.cipherText.pubKey.encrypt(-1n * plainText, 1n));
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// Shift the challenge down by 1 to ensure it is smaller than either prime factor.
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this.challenge = cryptoRandom(2048) << 1n;
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this.a = a;
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}
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verify(proof) {
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// check coprimality
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if (gcd(proof, this.cipherText.pubKey.n) !== 1n) return false;
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if (gcd(this.cipherText.cyphertext, this.cipherText.pubKey.n) !== 1n)
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return false;
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if (gcd(this.a, this.cipherText.pubKey.n) !== 1n) return false;
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// check exp
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return (
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mod_exp(proof, this.cipherText.pubKey.n, this.cipherText.pubKey.n ** 2n) ===
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(this.a *
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mod_exp(
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this.cipherText.cyphertext,
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this.challenge,
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this.cipherText.pubKey.n ** 2n
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)) %
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this.cipherText.pubKey.n ** 2n
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);
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}
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}
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window.ReadOnlyCyphertext = ReadOnlyCyphertext;
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export class PaillierPubKey {
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constructor(n) {
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this.n = n;
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this.g = this.n + 1n;
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}
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encrypt(m, r) {
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return new Cyphertext(this, m, r);
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}
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toJSON() {
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return {
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n: "0x" + this.n.toString(16),
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};
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}
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static fromJSON(data) {
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return new PaillierPubKey(BigInt(data.n));
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}
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}
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class PaillierPrivKey {
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constructor(p, q) {
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this.n = p * q;
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this.lambda = (p - 1n) * (q - 1n);
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this.mu = mod_exp(this.lambda, this.lambda - 1n, this.n);
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}
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decrypt(c) {
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return (
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(((mod_exp(c, this.lambda, this.n ** 2n) - 1n) / this.n) * this.mu) % this.n
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);
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}
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}
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export function generate_keypair() {
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let p, q, pubKey, privKey;
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if (window.sessionStorage.getItem("p") === null) {
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p = generate_prime();
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window.sessionStorage.setItem("p", p);
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} else {
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p = BigInt(window.sessionStorage.getItem("p"));
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}
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if (window.sessionStorage.getItem("q") === null) {
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q = generate_prime();
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window.sessionStorage.setItem("q", q);
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} else {
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q = BigInt(window.sessionStorage.getItem("q"));
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}
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pubKey = new PaillierPubKey(p * q);
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privKey = new PaillierPrivKey(p, q);
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return { pubKey, privKey };
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}
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