Add method to check whether cross-signing has keys

src/crypto/index.js

@@ -328,6 +328,15 @@ Crypto.prototype.checkPrivateKey = function(privateKey, expectedPublicKey) {
     }
 };
 
+/**
+ * Check whether we already have cross-signing keys for the current user.
+ *
+ * @return {boolean} Whether we have keys.
+ */
+Crypto.prototype.doesCrossSigningHaveKeys = function() {
+    return this._crossSigningInfo.hasKeys();
+};
+
 /**
  * Generate new cross-signing keys.
  *