RSA keygen. some other stuff

static/js/modules/crypto/main.js

@@ -1,2 +1,4 @@
 import { generate_keypair } from "./paillier.js";
-export { generate_keypair };
+import { generate_rsa_keypair } from "./rsa.js";
+
+export { generate_keypair, generate_rsa_keypair };

static/js/modules/crypto/math.js

@@ -12,3 +12,24 @@ export function mod_exp(a, b, n) {
 
     return res;
 }
+
+export function mod_inv(a, n) {
+    let t = 0n;
+    let new_t = 1n;
+    let r = n;
+    let new_r = a;
+
+    while (new_r !== 0n) {
+        let quotient = r / new_r;
+        t = new_t;
+        new_t = t - quotient * new_t;
+        r = new_r;
+        new_r = r - quotient * new_r;
+    }
+
+    if (t < 0) {
+        t = t + n;
+    }
+
+    return t;
+}

static/js/modules/crypto/rsa.js

@@ -0,0 +1,47 @@
+import { generate_prime } from "./random_primes.js";
+import { mod_exp, mod_inv } from "./math.js";
+
+let p, q, pubKey, privKey;
+
+class PubKey {
+    constructor(p, q) {
+        this.n = p * q;
+        this.e = 65537;
+    }
+
+    decrypt(m) {
+        return mod_exp(m, this.e, this.n);
+    }
+}
+
+class PrivKey {
+    constructor(p, q) {
+        this.n = p * q;
+        this.d = mod_inv(65537, (q - 1) * (p - 1));
+    }
+
+    encrypt(c) {
+        return mod_exp(c, this.d, this.n);
+    }
+}
+
+export function generate_rsa_keypair() {
+    if (window.sessionStorage.getItem("rsa_p") === null) {
+        p = generate_prime();
+        window.sessionStorage.setItem("rsa_p", p);
+    } else {
+        p = BigInt(window.sessionStorage.getItem("rsa_p"));
+    }
+
+    if (window.sessionStorage.getItem("rsa_q") === null) {
+        q = generate_prime();
+        window.sessionStorage.setItem("rsa_q", q);
+    } else {
+        q = BigInt(window.sessionStorage.getItem("rsa_q"));
+    }
+
+    pubKey = new PubKey(p, q);
+    privKey = new PrivKey(p, q);
+
+    return { pubKey, privKey };
+}