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Ruoyang Rykie Guo

Stevens Institute of Technology

I am in my third year pursuing my second PhD in electrical and computer engineering at Stevens Institute of Technology. Previously, I completed my first PhD and BS in computer science at Renmin University of China. I always focus on advancing the uncharted frontiers of Applied Cryptography, exploring Theoretical foundations to deal with emerging security and privacy challenges, with particular emphasis on AI-related threats.


Latest Advances in Theory

For decades, proof systems have relied on coin toss philosophy to capture randomness, helping us validate whether a cipher is secure or not. The AI era, however, has shifted privacy demands towards more flexible and tunable proof systems. Thinking in reverse, this tunability, e.g., for leakage, requires capturing determinism. Provable quantifiable security for measuring privacy should be considered if such a proof system is theoretically sound - while I believe she exists.

Below is a prototype of A Leakage-Guessing Proof System for privacy analysis:

Design Philosophy -- The design of this framework is driven by cross-referencing system ideology. If we talk about leakage, we mean leakage relative to some reference state, so a mirror construction is derived alongside the real construction. An assumption is invoked here: all elements in the mirror construction are fully protected (assumed perfect security). By 'all elements,' we mean everything from data and its expression down to storage—including content, organizing methods (indices), inter-connections (pointers), and server locations. Of course, this mirror construction lacks computational functionalities, while it serves as a "perfect" reference to expose leakage in the real construction that it mirrors. To simulate the reduction from $\Pi_{Real}$ to $\Pi_{Mirror}$, we follow the traditional cross-query pattern between an S and an A to derive a game. Unlike coin-toss philosophy, this game extracts deterministic information through a rule-based leakage-crawling chain at which place search/update patterns lie. (When discussing search/update pattern, we consider leaked statistical information about data.)

Then, the design logic of chess game C works as follows: a simulator S that simulates reduction from $\Pi_{Real}$ to $\Pi_{Mirror}$ is invoked to expose what leaked in real versus mirror. Since S needs to crawl the leaked information and such information requires plaintexts -- meaning it must invoke Enc/Dec oracles for each cipher in mirror -- we additionally introduce another role: Guard G to handle this process. Acting as an idealized reference state with a God's-eye view, G reverses the cipher-to-message trajectory. Its existence ensures messages reversed from $\Pi_{Mirror}$'s ciphers retain their original content and connections. Following the leakage-crawling chain, S continuously queries G for the needed information. Finally, S can respond with the result to the adversary A; and the simulator running this game can use it to measure the leakage proportion/range/level compared to the complete database. This is exactly what we are looking for: the leakage and its measuring. In other words, the leakage-crawling chain translating search/update pattern into rules gets transferred to the S-G interaction layer, which dictates the cross-query modes how G and S interact with each other.

The above proof system has been used for analyzing privacy in the work below, [1]: Threshold-Protected Searchable Sharing: Privacy Preserving Aggregated-ANN Search for Collaborative RAG.
: I am sincerely looking for collaborations to develop this theory or chase sky-bound ideas!

What Lacks in Current Framework?
  • Since that work considers data stored locally rather than on servers, the leakage-crawling chain defined in ref.[1] does not consider update patterns. Incorporating these new leaking modes (e.g., update patterns) into the chain rules would be an interesting try, which would accordingly bring modifications to the cross-query interactions between S and G in game C.
  • There could exist more flexible leakage-crawling chain rules for privacy analysis, not limited to search problems but extending to wider computation problems.
  • ...
  • 💡 A few Thoughts ---

    " This is an uncharted area with numerous possibilities and fun, alongside risks. A specific direction awaits wherever this path leads, waiting to be explored, sooner or later ~ "


    Selected Publications