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arXiv2026

Session Attestation for Unmodified TLS Services in Confidential Virtual Machines

Confidential cloud services aim to protect sensitive requests from the infrastructure that executes them. However, running a service inside a trusted execution environment does not ensure that users' plaintext appears only within the protected environment. We formulate Endpoint-Substitution Relay (ESR), a common attack outcome in which an adversary receives plaintext at a client-accepted endpoint while relaying requests to the legitimate service to preserve correct behavior. We present TLSLatch, a transparent session-attestation mechanism for services running in confidential virtual machines. TLSLatch attests the protected origin of the server's ephemeral TLS 1.3 key share and gates outbound traffic until verification succeeds. It requires no changes to applications, TLS libraries, certificates, or application protocols, and adds no extra payload-encryption layer. We implement TLSLatch with a hardware-backed Hygon CSV CVM server and clients on Linux, Windows, and macOS. Across these platforms, TLSLatch reduces completion time for 1KB requests by 56.9%--65.5% compared with nested TNG, and for 64MB requests by 43.8%--82.4% compared with CMaaS using application-key reuse. These results show that transparent session attestation can preserve existing TLS stacks while adding low-overhead endpoint binding to confidential cloud services.

cs.CR↗

arXiv2025

Practical Traceable Over-Threshold Multi-Party Private Set Intersection

Multi-Party Private Set Intersection (MP-PSI) with threshold enhances the flexibility of MP-PSI by disclosing elements present in at least $t$ participants' sets, rather than requiring elements to appear in all $n$ sets. In scenarios where each participant is responsible for its dataset, e.g., digital forensics, MP-PSI with threshold should disclose both intersection elements and corresponding holders such that elements are traceable and the reliability of intersection is guaranteed. We refer to MP-PSI with threshold supporting traceability as Traceable Over-Threshold MP-PSI (T-OT-MP-PSI). However, research on such protocols remains limited, and existing work tolerates at most $t-2$ semi-honest participants at considerable computational cost. We propose two novel Traceable OT-MP-PSI protocols. The first, Efficient Traceable OT-MP-PSI (ET-OT-MP-PSI), combines Shamir's secret sharing with an oblivious programmable pseudorandom function, achieving significantly improved efficiency with resistance to at most $t-2$ semi-honest participants. The second, Security-enhanced Traceable OT-MP-PSI (ST-OT-MP-PSI), achieves security against up to $n-1$ semi-honest participants by further leveraging the oblivious linear evaluation protocol. Compared to Mahdavi et al.'s protocol, ours eliminate the assumption that certain special parties do not collude. Experimental results demonstrate significant improvements: for $n=5$, $t=3$, and sets of size $2^{14}$, ET-OT-MP-PSI achieves $15056\times$ speedup and ST-OT-MP-PSI achieves $505\times$ speedup over Mahdavi et al.'s protocol.

cs.CR↗