Sean Purcell Software Engineer in training     Projects     Resume


Various projects I’ve created over the years that I am happy with.


An end-to-end encrypted chat program written in C from scratch using my ibcrypt library to provide cryptographic primitives. It uses a variety of algorithms such as RSA, Diffie-Hellman, scrypt, SHA2, CHACHA, and HMAC to provide key negotation, secure communication, and untamperable file storage. Additionally, it features several custom-written network protocols and message formats to ensure secure communications without requiring trusting the central server, allowing for the advantages of a decentralized system without the inherent security risk.


A realtime ray-tracer that implements gravitational lensing around a Schwarzschild black hole. It’s written in Rust, using the Glium library for window creation and GL context management, and with the ray tracing written in the fragment shader using Runge-Kutta 4 for stable integration.


A flight simulator written in C++ using OpenGL for rendering a 3D environment. It generates infinite terrain using simplex noise generation, with a pastel-like shading style that makes the terrain nice to look at. I also ported it to iOS using Google Cardboard to fly around in VR!


A cryptographic primitive library written in C. It was written to try my hand at writing cryptographic primitives as well as learn C. Implements various block ciphers, hash functions, key derivation functions, etc., as well as features an efficient arbitrary precision arithmetic implementation.


An Android app that allows you to determine the resistance of resistors by aiming your camera at it. It uses custom computer vision algorithms to locate the bands on resistors and then determine their colours. Created for the Tech Retreat 2015 hackathon, where it won 2nd place.


A combination of an Android app and web app that allows you to record videos from your phone straight to our webserver. It allows anyone to easily and anonymously record incidents to enable emergency responders and promote accountability. Its built on a combination of a java backend talking to the Android app, and a Rails webserver to run the webpage. It was created for Hack the North 2015, where it was one of the 12 winning teams.

My primary contribution was the communication between the phones and the backend, serializing the frames into an efficient format that could be sent over UDP and parsed on the other end for display.

This site

A static site made using the Jekyll site generator served by NGINX, with a dynamic background of snippets of code I wrote from various projects. It works with a NGINX configuration indicating that the background image file not be cached by the client, and to reverse proxy requests for the background image to a Flask server that returns a random image, selected from a number of images pregenerated with a custom tool working with Pygments.


A command-line based password manager written in C for Unix-based systems (i.e. OS X, Linux). Generates and stores passwords in a database file encrypted using chacha. The encryption and authentication keys are derived using scrypt and database file authenticated using HMAC-SHA256. It uses the ibcrypt library for implementations of cryptographic primitives.

3D Pacman

A 3D recreation of the classic arcade game “Pacman” written in Java. The rendering engine is a ray-caster written from scratch entirely in software. The ghost AI, level design, point counts, etc. are all faithfully recreated from the original game, the caveat being you can only see forward.