Mid refactor to stop polluting the namespace so much

static/js/modules/crypto/main.js

@@ -0,0 +1,2 @@
+import { generate_keypair } from "./paillier.js";
+export { generate_keypair };

static/js/modules/crypto/math.js

@@ -0,0 +1,14 @@
+export function mod_exp(a, b, n) {
+    let res = 1n;
+
+    while (b > 0n) {
+        if (b % 2n === 1n) {
+            res = (res * a) % n;
+        }
+
+        b >>= 1n;
+        a = (a * a) % n;
+    }
+
+    return res;
+}

static/js/modules/crypto/paillier.js

@@ -0,0 +1,61 @@
+import { random2048, generate_prime } from "./random_primes.js";
+import { mod_exp } from "./math.js";
+
+let p, q, pubKey, privKey;
+
+class PubKey {
+    constructor(p, q) {
+        this.n = p * q;
+        // this.g = this.n + 1n;
+    }
+
+    encrypt(m) {
+        // Compute g^m r^n mod n^2
+        let r = random2048();
+
+        // Resample to avoid modulo bias.
+        while (r >= this.n) {
+            r = random2048();
+        }
+
+        // Compute g^m by binomial theorem.
+        let gm = (1n + this.n * m) % this.n ** 2n;
+        // Compute g^m r^n from crt
+        return (gm * mod_exp(r, this.n, this.n ** 2n)) % this.n ** 2n;
+    }
+}
+
+class PrivKey {
+    constructor(p, q) {
+        this.n = p * q;
+        this.lambda = (p - 1n) * (q - 1n);
+        this.mu = mod_exp(this.lambda, this.lambda - 1n, this.n);
+    }
+
+    decrypt(c) {
+        return (
+            (((mod_exp(c, this.lambda, this.n ** 2n) - 1n) / this.n) * this.mu) % this.n
+        );
+    }
+}
+
+export function generate_keypair() {
+    if (window.sessionStorage.getItem("p") === null) {
+        p = generate_prime();
+        window.sessionStorage.setItem("p", p);
+    } else {
+        p = BigInt(window.sessionStorage.getItem("p"));
+    }
+
+    if (window.sessionStorage.getItem("q") === null) {
+        q = generate_prime();
+        window.sessionStorage.setItem("q", q);
+    } else {
+        q = BigInt(window.sessionStorage.getItem("q"));
+    }
+
+    pubKey = new PubKey(p, q);
+    privKey = new PrivKey(p, q);
+
+    return { pubKey, privKey };
+}