...

static/js/modules/crypto/paillier.js

@@ -15,8 +15,14 @@ class Cyphertext {
         // Compute g^m by binomial theorem.
         let gm = (1n + key.n * plainText) % key.n ** 2n;
 
-        // Compute g^m r^n from crt
+        // Compute g^m r^n from crt.
         this.cyphertext = (gm * mod_exp(r, key.n, key.n ** 2n)) % key.n ** 2n;
+
+        // Force into range.
+        while (this.cyphertext < 0n) {
+            this.cyphertext += key.n ** 2n;
+        }
+
         this.r = r;
         this.pubKey = key;
         this.plainText = plainText;