Building end-to-end applications is not easy, or at the very least, it comes with its own unique set of challenges. There are the often talked about challenges, like making sure you use battle tested encryption primitives and use them correctly, and striking the balance between security and usability. Unfortunately, there are many more challenges that are not often talked about, like the significantly decreased development speed due to all the code being implemented on the client side, the increased difficulty and complexity in upgrading the protocol and many others. In this talk Tom will use EteSync as an example for a secure application to show some of the more interesting challenges he faced while creating it, and new challenges that he encountered as the user-base grew and the protocol evolved. Tom will also cover some of the issues that affect EteSync today, how they will be addressed in the future, where EteSync is going, and what's currently holding it back. By the end of this talk, attendees will be made familiar with some of the unique challenges that come with building end-to-end encrypted applications and some alternatives for solving them. Audience: People interested in the inner workings of EteSync Developers interested in, or actively designing secure applications and protocols People interested in the future of the EteSync