From the programming perspective, synchronization and availability along with privacy and security concerns add significant challenges. REScala combines advanced functional reactive programming with replicated data types to ensure automatic updates and eventual consistency, thus relieving developers from this complexity so that they can focus on the business logic of the application. However, normally the use of replicated data types requires that developers redesign their application to fit to the pre-defined set of operations and data types, moreover, storage of data on untrusted intermediaries for added reliability is often not considered. To address these issue, we design an easy-to-use programming model that allows developers to design application-specific replicated data types, which also enable automatic encryption and authentication. We show that our approach is suitable to encrypt communication between local-first applications while retaining coordination freedom.