Date of Award


Document Type


Degree Name

Master of Science (MS)


Computer Engineering and Sciences

First Advisor

Marius C. Silaghi

Second Advisor

William H. Allen

Third Advisor

Nezamoddin Nezamoddini-Kachouie

Fourth Advisor

Philip J. Bernhard


An instant messaging service designed using a peer to peer distributed network architecture has many appealing properties it gets for free: high scalability, cheap operational cost and no reliance on a third party to provide the service. However, the nature of the distributed network architecture makes implementing some of the instant messaging features rather challenging, asynchronous messaging being one of them. The asynchronous messaging requires that peers store arbitrary data on behalf of other peers for prolonged periods of time, often measured in days, which, if not kept in check, can be easily abused by malicious actors by spamming the network with bogus store requests, resulting in a storage exhaustion of the network and DoS of the asynchronous messaging feature. In this thesis we present two reputation-based techniques against the storage exhaustion DoS attack – a local knowledge one, in which the reputation is tracked by a small group of peers, and a global knowledge one, in which all peers keep track of the reputation on a blockchain ledger. We discuss the security, overhead and scalability of the techniques. We implement a Kademlia DHT that acts as an overlay network for our peer to peer distributed messaging service, we implement the defense techniques and measure their performance, and we simulate the attack on the messaging service and measure the success rate of the implemented defense techniques.


Copyright held by author.