groups key generation bug fix

WASignalGroup/keyhelper.js

@@ -0,0 +1,21 @@
+const curve = require('libsignal/src/curve');
+const nodeCrypto = require('crypto');
+
+exports.generateSenderKey = function() {
+    return nodeCrypto.randomBytes(32);
+}
+
+exports.generateSenderKeyId = function() {
+    return nodeCrypto.randomInt(2147483647);
+}
+
+exports.generateSenderSigningKey = function(key) {
+    if (!key) {
+        key = curve.generateKeyPair();
+    }
+
+    return {
+        public: key.pubKey,
+        private: key.privKey,
+    };
+}