Dionysis is a post-doc at Stanford's Electrical Engineering department. He holds a PhD in Cryptography from the University of Athens and a MEng in Electrical and Computer Engineering from the National Technical University of Athens. His research interests focus on the consensus layer of proof-of-work and proof-of-stake blockchains. He has published in academic and industry conferences such as IEEE Security & Privacy (Oakland), ACM Computer and Communications Security (CCS), ESORICS, Financial Crypto, ACM Advances in Financial Technologies (AFT), Black Hat Europe, and Black Hat Asia. In the past, he worked in the Security Incident Response team of Google in Zürich and as a Full Stack Software Engineer at deviantART, and interned at the Product Security team of Twitter in San Francisco.

Stanford Advisors

Current Research and Scholarly Interests

I am interested in permisionless (trustless and decentralized) blockchain systems that use proof-of-work or proof-of-stake consensus. On the consensus layer, I am interested in the bootstrapping problem and the question of synchronizing from genesis succinctly (using logarithmic communication and storage) in proof-of-work (Non-Interactive Proofs of Proof-of-Work – NIPoPoWs) and proof-of-stake (Proofs of Proof-of-Stake – PoPoS).

These protocols can also be used for cross-chain communication and interoperability, and creating bridges between multiple chains. It can also allow a blockchain's smart contracts to consume its own data. This has many applications in decentralized finance.

I like creating systems that can be deployed in a backwards-compatible manner using soft forks or velvet forks. I am also interested in the safe upgradability of blockchains.

I study the use of exotic cryptographic primitives (such as witness encryption and timelock encryption) to build interesting schemes on top of blockchains such as wallets and fair exchanges. On the problem of fair exchange, I am also interested in decentralized anonymous marketplaces such as OpenBazaar.

I have a lot of interest in creating Sybil-resilient trust and reputation systems on top of decentralized platforms such as blockchains. These can be used to build decentralized search, decentralized content sharing platforms for music, books, and movies (where creators can be fairly compensated), and decentralized censorship-resistant social networking. I am looking for ways of doing this.

I enjoy studying and analyzing how privacy-enhancing censorship-resistant technologies such as Tor are used. Other technologies of interest are Signal and other end-to-end encrypted open source messaging systems.

Lastly, I am interested in the ethical questions of blockchains, whether they are a net good or bad for the world, and the political ramifications of their adoption in the world economy.

In the past, I worked on analyzing the security of the composition of encryption and compression in attacks against RC5 and AES used in HTTPS (BREACH).

2022-23 Courses