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Jinchun He

Publications and source records attributed to Jinchun He.

7 recordsLinked to original sources
arXiv2026

Breaking Cycles for Scalable Fair Ordering in Blockchain Systems

In blockchain systems, transaction order directly determines financial outcomes: unfair ordering enables front-running and sandwich attacks that have extracted over \$686M from Ethereum users. Current fair-ordering protocols aggregate pairwise receive-order evidence from replicas. Under contention or adversarial manipulation, however, Condorcet cycles force them into global strongly connected component (SCC) condensation, causing delays, coarse batches, and scaling failures. We present FlashOrder, a deterministic fair-ordering engine that localizes cyclic ambiguity before it propagates across the batch. FlashOrder embeds pairwise preferences into one-dimensional canonical positions, clusters nearby transactions with a partition hypergraph, and performs hierarchical inter- and intra-cluster serialization, replacing batch-wide SCC condensation with localized sorting and aggregation. Evaluated against Themis (CCS '23) and Rashnu (VLDB '24) on a libhotstuff-based prototype, FlashOrder achieves up to 10.5$\times$ higher throughput than Themis and 4.8$\times$ higher than Rashnu, with the latency gap widening as network scales. In controlled adversarial simulation, it reduces maximum rank displacement by 88.7\%, and under Condorcet attacks it sustains 12.0$\times$ and 9.7$\times$ higher throughput than Themis and Rashnu on average. These results show that localizing cyclic ambiguity yields stronger fairness at substantially higher throughput.

cs.DC↗
arXiv2026

E-MIA: Exam-Style Black-Box Membership Inference Attacks against RAG Systems

Retrieval-Augmented Generation (RAG) equips large language models (LLMs) with external evidence by retrieving documents at inference time, but it also turns the retrieval corpusinto a sensitive asset. Under a black-box setting, an adversary given a candidate document can infer whether it has been ingested into the RAG knowledge base (i.e., document-level membership inference) solely from query response interactions, thereby leaking corpus coverage and the existence of sensitive topics. Existing RAG MIA methods either rely on soft signals such as semantic similarity, which often yield overlapping member/non-member score distributions and unstable thresholds, or employ explicit confirmation probes whose intent is conspicuous and thus prone to refusal and detection. We propose E-MIA, which converts verifiable hard evidence in the target document (e.g., fine-grained details, proper nouns/technical terms, definitional statements, metadata cues, and causal/constraint relations) into an exam with four objectively gradable question types (FB/SC/MC/T/F), and uses the aggregated exam score across multiple evidence targeted questions as the membership signal. Experiments across multiple datasets and diverse RAG configurations demonstrate that E-MIA improves member/non-member separability in stringent settings while preserving natural, stealthy queries, and we further analyze the impact of question composition and exam length on attack effectiveness.

cs.CR↗
arXiv2018

Positive ground state solutions for fractional Laplacian system with one critical exponent and one subcritical exponent

In this paper, we consider the following fractional Laplacian system with one critical exponent and one subcritical exponent \begin{equation*} \begin{cases} (-Δ)^{s}u+μu=|u|^{p-1}u+λv & x\in \ \mathbb{R}^{N}, (-Δ)^{s}v+νv = |v|^{2^{\ast}-2}v+λu& x\in \ \mathbb{R}^{N},\\ \end{cases} \end{equation*} where $(-Δ)^{s}$ is the fractional Laplacian, $0 2s, \ λ<\sqrt{μν},\ 1 μ_{0}$, there exists a $λ_{μ,ν}\in[\sqrt{(μ-μ_{0})ν},\sqrt{μν})$ such that if $λ>λ_{μ,ν}$, the system has a positive ground state solution, if $λ<λ_{μ,ν}$, the system has no ground state solution.

math.AP↗
arXiv2017

Critical system involving fractional Laplacian

In this paper, we study the following critical system with fractional Laplacian: \begin{equation*} \begin{cases} (-Δ)^{s}u= μ_{1}|u|^{2^{\ast}-2}u+\frac{αγ}{2^{\ast}}|u|^{α-2}u|v|^β \ \ \ \text{in} \ \ \mathbb{R}^{n}, (-Δ)^{s}v= μ_{2}|v|^{2^{\ast}-2}v+\frac{βγ}{2^{\ast}}|u|^α|v|^{β-2}v\ \ \ \ \text{in} \ \ \mathbb{R}^{n}, u,v\in D_{s}(\mathbb{R}^{n}). \end{cases} \end{equation*} By using the Nehari\ manifold,\ under proper conditions, we establish the existence and nonexistence of positive least energy solution of the system.

math.AP↗
arXiv2014

Approximation of the inertial manifold for a nonlocal dynamical system

We consider inertial manifolds and their approximation for a class of partial differential equations with a nonlocal Laplacian operator $-(-Δ)^{\fracα{2}}$, with $0<α<2$. The nonlocal or fractional Laplacian operator represents an anomalous diffusion effect. We first establish the existence of an inertial manifold and highlight the influence of the parameter $α$. Then we approximate the inertial manifold when a small normal diffusion $\varepsilon Δ$ (with $\varepsilon \in (0, 1)$) enters the system, and obtain the estimate for the Hausdorff semi-distance between the inertial manifolds with and without normal diffusion.

math.AP↗
arXiv2013

Global solutions for a nonlocal Ginzberg-Landau equation and a nonlocal Fokker-Plank equation

This work is devoted to the study of a nonlocal Ginzberg-Landau equation by the semigroup method and a nonlocal Fokker-Plank equation by the viscosity vanishing method. For the nonlocal Ginzberg-Landau equation, there exists a unique global solution in the set $C^0(\mathbb{R}^+,\,H_0^{\fracα{2}}(D))\cap L_{loc}(\mathbb{R}^+,\,H_0^α(D))$, for $α\in (0,\,2)$. For the nonlocal Fokker-Plank equation, the regularity of the solution is weaker than that of the nonlocal Ginzberg-Landau equation due to the drift term.

math.AP↗