Álvaro Castro-Castilla

Murmur is a platform for Secure Data Storage and Secure Multi-Party Computation. It is backed by an untamperable distributed log (with strong similarities to a blockchain). It employs Shamir Secret Sharing for information-theoretical security while leveraging the power of MPC operating on that data without ever decrypting it. Thus, the data remains secure even at the time of its usage, so it doesn't require to be decrypted (under a certain set of constraints).

It's built using Go and implements interesting features such as:
- A custom consensus algorithm (first a custom implementation of XFT was used, then migrated to an in-house variation of HotStuff).
- Tracing end-to-end, based on Opentracing.
- Network bootstrapping, both based in UDP broadcasting discovery and a central service registry.
- In order to accelerate development, we created centralized versions of algorithms that we knew could be fully distributed, effectively rendering the design fully decentralized, but moving in stages towards that objective.

My role in this project was as the team leader (as CTO/cofounder of the company).

Cointrust is a prototype P2P Bitcoin marketplace built on top of Facebook. A user puts a bid or sell request, and the system matches users based on the social graph. Once this match is performed, a legally-binding process is initiated to secure a transaction between the two parties. The system handles the Bitcoin payment itself (by tracking the payment as being performed to the given address), finalizing the transaction.

The project is a full-stack application built in Clojure/Clojurescript, using PostgreSQL and custom Java code bindings for the Bitcoin network interop. Frontend-backend communication is handled via WebSockets.

I designed (UI/UX and technical), architected and implemented the web app and infrastructure for iKidz English, which aims at providing its early-age English as foreign language academies with comprehensive software. It provides 4 different interfaces:
- A web interface for kids to use during classroom time. It offers a very simple interface based on a single search field that will filter tasks/activities to be selected by the students. They will then work in the class together in that activity. The progress will be monitored and screenshots will be taken at preset times.
- A web interface for parents, for payments and to track their children's progress.
- A web interface for academy owners (managers), that will manage payments, parents, classrooms (groups) and students. It offers also a form of communication with parents, and a way to control the class live (like simultaneously starting the same activity in all the students' tablet).
- An admin interface to tag and edit activities and managers, as well as monitor payments.

The technology stack consisted of Clojure/Clojurescript and PostgreSQL. front end-back end communication was handled via WebSockets.

I built the first version in Go of this proxy, that was intended as a substitute of the old Java-based used within the company. It was later deployed in a fleet of over 10k at its peak times. Some of the extensions to the regular HTTP forwarding and TLS tunneling performed by the proxy involved:
- Selective throttling
- Custom protocol for traffic shaping
- Data monitoring and traffic sampling (anonymized)
- A pseudo-authentication system to allow for a certain degree of limitation (used for separating the free from the paid versions of the system).

It was implemented in pure Go and used Redis as a back end for metrics storage.

SchemeSpheres is a set of libraries and development tools for making multiplatform applications in Scheme feasible. It provides many libraries commonly seen in standard libraries of other languages, tailored for the Scheme Gambit compiler. It's a multi-year solo project intended to give the Gambit Scheme community the most comprehensive attempt to unify a fragmented landscape of real-world tools and projects.

Some of its highlights are:
- +150 libraries, including data structures, algorithms, basic web libraries, and graphics (OpenGL and Cairo).
- Easy-to-use multiplatform and flexible build tasks runner (supporting Linux, OSX, Windows, Android, and iOS).
- Tools for interactive and remote development in all these platforms, mixing optimized compiled code with interpreted and live coding.

I contributed to the open-source Gambit Scheme implementation by providing it with TLS support in the runtime. This allowed full control of the TCP connections to be upgraded to TLS, in an easy and idiomatic way for the Scheme implementation users.

This was a very interesting learning experience that required diving into the internals of the OS and network parts of the runtime. The code was a combination of C (runtime) and Scheme (exposed functionality).

As a digital artist, I worked with scientists, artists, and engineers to develop software and software-as-research, in several cases for national and international exhibitions. I created and explored new possibilities of visual, haptic and artistic expression and information visualization throughout the means of computation. These explorations were about the topics of complex processes, self-organization, evolutionary algorithms, AI, endosymbiosis, and epigenetics.

My work was exhibited in Ars Electronica (Linz, Austria), Zentrum für Kunst und Medientechnologie (Karlsruhe, Germany), LABoral (Gijón, Spain), Medialab Madrid (Madrid, Spain), Puertas de Castilla (Murcia, Spain), and CAB (Burgos, Spain).

I was a key component of the core initial team involved in the university creation and definition process. I spearheaded the design and definition of the academic model and directed the creation of studies curricula for 5 B.A./B.Sc. programs and a M.Sc. in Graphic Programming and Simulation. I conducted meetings with specialists and developed curriculum structures. My focus was on developing the multidisciplinary approach in U-tad's education model. During this period, I helped in interviewing candidate professors, and my role was key during the selection process of the first batch for the university.