Graduation Semester and Year




Document Type


Degree Name

Master of Science in Computer Science


Computer Science and Engineering

First Advisor

Matthew Wright


Instant messaging is one of the most used modes of communication and there are many instant messaging systems available online. Studies from the Electronic Frontier Foundation show that there are only a few instant messengers that keep your messages safe by providing ,security and limited anonymity. Lilac, a Lightweight Low-latency Anonymous Chat, is a secure instant messenger that provides security as well as better anonymity to users as compared to other messengers. It is a browser-based instant messaging system that uses Tor like a model to protect user anonymity. Compared to existing messengers, LILAC protects the users from tra?c analysis by implementing cover tra?c. It is built on OTR (O? the Record) messaging to provide forward secrecy and implements Socialist Millionaire Protocol to guarantee the user authenticity. Unlike other existing instant messaging systems, it uses pseudonyms to protect user anonymity. Being a browser-based web application, it does not require any installation and it leaves no footprints to trace. It provides user to save contact details in a secure way, by an option to download the contacts in an encrypted file. This encrypted file can be used to restore the contacts later. In our experimentation with Lilac, we found the Round Trip Time (RTT) for a message is around 3.5 seconds which is great for a messenger that provides security and anonymity. Lilac is readily deployable on di?erent and multiple servers. In this document, we provide in-depth details about the design, development, and results of LILAC.


LILAC, Anonymous chat, Lightweight, Secure, Presence server, Directory, Relays


Computer Sciences | Physical Sciences and Mathematics


Degree granted by The University of Texas at Arlington