DP-MemView: A Memory Interface for Attribute-Level Transcript Privacy in Long-Term LLM Agents

AuthorsJong Wook Kim, Byoungjae Min, Kennedy Edemacu et al.

arXiv 20262026

TL;DR

DP-MemView privately selects public memory views with per-attribute DP ledgers, keeping transcript AUC near 0.49 while preserving personalization quality around 0.88.

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THE PROBLEM

Cumulative Attribute Leakage Through Benign Personalization

Long-term memory enables persistent personalization, but repeated memory-conditioned responses can cumulatively reveal protected attributes even when never stated explicitly.

In a meal-planning assistant, ordinary queries yield blood-sugar-conscious advice that lets a semi-trusted application infer type-2 diabetes from the observed transcript.

HOW IT WORKS

DP-MemView Memory-View Interface

DP-MemView centers on Slot-Level View Selection, Attribute Accounting, and the DP-MemView Interface Contract to privatize memory-conditioned views.

Think of DP-MemView as a privacy-aware memory controller: raw slots stay like protected disk blocks, while public views act like safe RAM hints for the LLM.

This design lets DP-MemView bound full adaptive transcripts with pure Ba-DP, something a plain context window or raw memory retrieval cannot guarantee.

DIAGRAM

Adaptive Transcript Flow With DP-MemView

This diagram shows how DP-MemView processes each turn of an adaptive application, from query to differentially private transcript entry.

DIAGRAM

Evaluation Pipeline and Safeguard Ablations

This diagram shows how DP-MemView is evaluated on PairedMem and public-corpus tracks, including baseline interfaces and safeguard ablations.

PROCESS

How DP-MemView Handles an Adaptive Transcript Session

  1. 01

    Slot-Level View Selection

    DP-MemView uses Slot(qt, ˜τ<t) to choose active slots Gt, then applies the read policy Rt,g to map queries onto memory positions.

  2. 02

    Attribute Accounting

    DP-MemView computes Γ⋆(Rt,g) and declares Γt,g, ensuring every intersecting protected group Ia is charged in the per-attribute ledgers La.

  3. 03

    Exponential Mechanism View Sampling

    Using the internal scorer ut,g and sensitivity bound ∆ut,g, DP-MemView samples a view vt,g from Vg with the exponential mechanism and local εt,g.

  4. 04

    Interface Contract and Transcript Release

    Under the DP-MemView Interface Contract, the response LLM KLLM receives only qt, vt, and τ<t, producing yt that composes into pure Ba-DP for ˜τT.

KEY CONTRIBUTIONS

Key Contributions

  • 01

    Adaptive Transcript Privacy Formulation

    DP-MemView formalizes long-term memory privacy as pure Ba-DP over full adaptive transcripts ˜τT, not single responses, with attribute-level adjacency M ∼a M′.

  • 02

    DP-MemView Interface Contract

    DP-MemView defines Conditions C1–C6, including fixed vocabularies Vg, complete charging Γt,g ⊇ Γ⋆(Rt,g), and pathwise caps La ≤ Ba with generic fallbacks.

  • 03

    Empirical Evaluation With Safeguard Ablations

    DP-MemView shows AUC near 0.49 and U around 0.88 across three LLMs, while ablations like CappedArgmax push AUC to 0.754 and break the Ba-DP bound.

RESULTS

By the Numbers

AUC

0.490

-0.352 vs RawReadSet on PairedMem with Qwen2.5-7B

TPR@5

0.016

-0.531 vs RawReadSet on PairedMem with Qwen2.5-7B

tRec

0.506

-0.015 vs RawReadSet on PairedMem with Qwen2.5-7B

U

0.877

+0.102 over RawReadSet on PairedMem with Qwen2.5-7B

On the PairedMem synthetic benchmark at T = 16 with Qwen2.5-7B, which tests attribute distinguishability under adjacent memory stores, DP-MemView (on) sharply reduces AUC while keeping overall utility U comparable to GenericOnly. This MAIN_RESULT shows DP-MemView can maintain near-chance transcript privacy without sacrificing personalization quality.

BENCHMARK

By the Numbers

On the PairedMem synthetic benchmark at T = 16 with Qwen2.5-7B, which tests attribute distinguishability under adjacent memory stores, DP-MemView (on) sharply reduces AUC while keeping overall utility U comparable to GenericOnly. This MAIN_RESULT shows DP-MemView can maintain near-chance transcript privacy without sacrificing personalization quality.

BENCHMARK

PairedMem Synthetic Track at T = 16 (Qwen2.5-7B)

AUC for different memory interfaces on PairedMem synthetic, measuring transcript-level attribute distinguishability.

BENCHMARK

Public-Corpus Transfer Track at T = 16 (Qwen2.5-7B)

AUC for DP-MemView and baselines on public-corpus transfer, using corpus-derived memory text.

KEY INSIGHT

The Counterintuitive Finding

DP-MemView (pre) achieves tRec up to 0.571 on PairedMem with Gemma-2-9B while keeping AUC as low as 0.464.

This is surprising because stronger personalization usually increases leakage, yet DP-MemView’s interface contract lets higher tRec coexist with near-chance attribute distinguishability.

WHY IT MATTERS

What this unlocks for the field

DP-MemView unlocks attribute-level differential privacy for entire adaptive transcripts, not just single answers or masked spans.

Builders can now connect long-term memory agents to semi-trusted applications while bounding how much transcripts can change adversaries’ prior odds about protected attributes.

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