Krishnaram Kenthapadi

NeurIPS Conference 2025 Conference Paper

Permissioned LLMs: Enforcing Access Control in Large Language Models

• Bargav Jayaraman
• Virendra Marathe
• Hamid Mozaffari
• William Shen
• Krishnaram Kenthapadi

In enterprise settings, organizational data is segregated, siloed and carefully protected by elaborate access control frameworks. These access control structures can completely break down if an LLM fine-tuned on the siloed data serves requests, for downstream tasks, from individuals with disparate access privileges. We propose Permissioned LLMs (PermLLM), a new class of LLMs that superimpose the organizational data access control structures on query responses they generate. We formalize abstractions underpinning the means to determine whether access control enforcement happens correctly over LLM query responses. Our formalism introduces the notion of a relevant response that can be used to prove whether a PermLLM mechanism has been implemented correctly. We also introduce a novel metric, called access advantage, to empirically evaluate the efficacy of a PermLLM mechanism. We introduce three novel PermLLM mechanisms that build on Parameter Efficient Fine-Tuning to achieve the desired access control. We furthermore present two instantiations of access advantage–(i) Domain Distinguishability Index (DDI) based on Membership Inference Attacks, and (ii) Utility Gap Index (UGI) based on LLM utility evaluation. We demonstrate the efficacy of our PermLLM mechanisms through extensive experiments on five public datasets (GPQA, RCV1, SimpleQA, WMDP, and PubMedQA), in addition to evaluating the validity of DDI and UGI metrics themselves for quantifying access control in LLMs.

NeurIPS Conference 2022 Conference Paper

Are Two Heads the Same as One? Identifying Disparate Treatment in Fair Neural Networks

• Michael Lohaus
• Matthäus Kleindessner
• Krishnaram Kenthapadi
• Francesco Locatello
• Chris Russell

We show that deep networks trained to satisfy demographic parity often do so through a form of race or gender awareness, and that the more we force a network to be fair, the more accurately we can recover race or gender from the internal state of the network. Based on this observation, we investigate an alternative fairness approach: we add a second classification head to the network to explicitly predict the protected attribute (such as race or gender) alongside the original task. After training the two-headed network, we enforce demographic parity by merging the two heads, creating a network with the same architecture as the original network. We establish a close relationship between existing approaches and our approach by showing (1) that the decisions of a fair classifier are well-approximated by our approach, and (2) that an unfair and optimally accurate classifier can be recovered from a fair classifier and our second head predicting the protected attribute. We use our explicit formulation to argue that the existing fairness approaches, just as ours, demonstrate disparate treatment and that they are likely to be unlawful in a wide range of scenarios under US law.

ICLR Conference 2022 Conference Paper

COPA: Certifying Robust Policies for Offline Reinforcement Learning against Poisoning Attacks

• Fan Wu 0011
• Linyi Li 0001
• Huan Zhang 0001
• Bhavya Kailkhura
• Krishnaram Kenthapadi
• Ding Zhao
• Bo Li 0026

As reinforcement learning (RL) has achieved near human-level performance in a variety of tasks, its robustness has raised great attention. While a vast body of research has explored test-time (evasion) attacks in RL and corresponding defenses, its robustness against training-time (poisoning) attacks remains largely unanswered. In this work, we focus on certifying the robustness of offline RL in the presence of poisoning attacks, where a subset of training trajectories could be arbitrarily manipulated. We propose the first certification framework, COPA, to certify the number of poisoning trajectories that can be tolerated regarding different certification criteria. Given the complex structure of RL, we propose two certification criteria: per-state action stability and cumulative reward bound. To further improve the certification, we propose new partition and aggregation protocols to train robust policies. We further prove that some of the proposed certification methods are theoretically tight and some are NP-Complete problems. We leverage COPA to certify three RL environments trained with different algorithms and conclude: (1) The proposed robust aggregation protocols such as temporal aggregation can significantly improve the certifications; (2) Our certifications for both per-state action stability and cumulative reward bound are efficient and tight; (3) The certification for different training algorithms and environments are different, implying their intrinsic robustness properties. All experimental results are available at https://copa-leaderboard.github.io.

ICML Conference 2022 Conference Paper

Generating Distributional Adversarial Examples to Evade Statistical Detectors

• Yigitcan Kaya
• Muhammad Bilal Zafar
• Sergül Aydöre
• Nathalie Rauschmayr
• Krishnaram Kenthapadi

Deep neural networks (DNNs) are known to be highly vulnerable to adversarial examples (AEs) that include malicious perturbations. Assumptions about the statistical differences between natural and adversarial inputs are commonplace in many detection techniques. As a best practice, AE detectors are evaluated against ’adaptive’ attackers who actively perturb their inputs to avoid detection. Due to the difficulties in designing adaptive attacks, however, recent work suggests that most detectors have incomplete evaluation. We aim to fill this gap by designing a generic adaptive attack against detectors: the ’statistical indistinguishability attack’ (SIA). SIA optimizes a novel objective to craft adversarial examples (AEs) that follow the same distribution as the natural inputs with respect to DNN representations. Our objective targets all DNN layers simultaneously as we show that AEs being indistinguishable at one layer might fail to be so at other layers. SIA is formulated around evading distributional detectors that inspect a set of AEs as a whole and is also effective against four individual AE detectors, two dataset shift detectors, and an out-of-distribution sample detector, curated from published works. This suggests that SIA can be a reliable tool for evaluating the security of a range of detectors.

ICML Conference 2021 Conference Paper

Differentially Private Query Release Through Adaptive Projection

• Sergül Aydöre
• William Brown
• Michael J. Kearns
• Krishnaram Kenthapadi
• Luca Melis
• Aaron Roth 0001
• Amaresh Ankit Siva

We propose, implement, and evaluate a new algo-rithm for releasing answers to very large numbersof statistical queries likek-way marginals, sub-ject to differential privacy. Our algorithm makesadaptive use of a continuous relaxation of thePro-jection Mechanism, which answers queries on theprivate dataset using simple perturbation, and thenattempts to find the synthetic dataset that mostclosely matches the noisy answers. We use a con-tinuous relaxation of the synthetic dataset domainwhich makes the projection loss differentiable, and allows us to use efficient ML optimizationtechniques and tooling. Rather than answering allqueries up front, we make judicious use of ourprivacy budget by iteratively finding queries forwhich our (relaxed) synthetic data has high error, and then repeating the projection. Randomizedrounding allows us to obtain synthetic data in theoriginal schema. We perform experimental evalu-ations across a range of parameters and datasets, and find that our method outperforms existingalgorithms on large query classes.

SODA Conference 2006 Conference Paper

Balanced allocation on graphs

• Krishnaram Kenthapadi
• Rina Panigrahy