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Research Summary

I am a doctorate candidate at BU Data Lab (MiDAS lab) under supervision of George Kollios. Here is my dissertation prospectus abstract.

As organizations struggle with processing vast amounts of information, outsourcing sensitive data to third parties becomes a necessity. To protect the data, various cryptographic techniques are used in outsourced database systems to ensure data privacy while allowing efficient querying.

I propose components of a new secure and efficient database system, which answers various types of queries, with different privacy guarantees in different security models. I start with my survey work on five order-preserving/revealing encryption schemes that can be used directly in many database indices, like the B+ tree, and five range query protocols with various trade-offs in terms of security and efficiency. This work systematizes the state-of-the-art range query solutions in a snapshot adversary setting and offers some non-obvious observations regarding the efficiency of the constructions. I then follow with a recently published work, $\mathcal{E}\text{psolute}$, an efficient range query engine in a persistent adversary setting. In this work, we achieve security in a setting with a much stronger adversary where she can continuously observe everything on the server, and leaking even the result size can enable a reconstruction attack. I then describe ongoing work on secure $k$-nearest-neighbor queries, in which the security is achieved similarly to OPE/ORE solutions - encrypting the input with a distance-comparison preserving encryption scheme, so the inputs are perturbed, but the query algorithm still produces accurate results. Finally, I conclude the presentation with another ongoing work targeting $\texttt{JOIN}$ queries in a persistent adversary setting. In this work, we are using an SGX enclave with its limited memory to process $\texttt{JOIN}$ queries in small batches in a way to hide both the result size and access pattern.

Interests

  • Database Security
  • Differential Privacy
  • Oblivious RAM (ORAM)
  • Algorithms over encrypted data
  • Secure (range) Query Protocols
  • Zero-knowledge proofs (including NIZK protocols)
  • Searchable Encryption
  • Order Revealing Encryption

Ph.D. milestones

Collaborators

Daria Bogatova

Neuroscience, Goethe-Universität Frankfurt am Main

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Pixel

The Cat

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George Kollios

Professor, BU

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Leo Reyzin

Professor, BU

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Georgios Kellaris

Independent Researcher

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Adam O'Neil

Assistant Professor, UMass Amherst

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Kobbi Nissim

Professor, Georgetown University

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Björn Tackmann

DFINITY

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