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arxiv: 2602.12614 · v2 · submitted 2026-02-13 · 💻 cs.IT · math.IT

Secure Beamforming for ISAC Systems Under Communication Eavesdropper and Sensing Eavesdropper

Tian Zhang , Zhirong Su , Yueyi Dong This is my paper

Pith reviewed 2026-05-15 22:41 UTC · model grok-4.3

classification 💻 cs.IT math.IT
keywords ISACphysical layer securitybeamformingsecrecy ratesensing eavesdroppercommunication eavesdropper
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The pith

Transmit beamforming for communication and sensing signals maximizes the secrecy rate of an ISAC system against both communication and sensing eavesdroppers.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper investigates physical layer security for integrated sensing and communication systems that face eavesdroppers on both the data links and the sensing function. It establishes that joint beamforming design across the two signal types raises the overall secrecy rate while satisfying sensing performance targets and total power limits. The authors convert the non-convex rate-maximization problem into an iterative sequence of convex subproblems via successive convex approximation, first-order Taylor expansion, and semidefinite relaxation. They further prove that the relaxation step introduces no optimality gap. This result matters because future wireless systems that share hardware between radar and communications must protect both functions from interception without sacrificing efficiency.

Core claim

The system secrecy rate is maximized by transmit beamforming design of communication and sensing signals when taking sensing security, sensing performance and transmit power constraint into consideration. To deal with the formulated non-convex optimization problem, the successive convex approximation together with the first-order Taylor expansion and semidefinite relaxation is utilized. It is theoretically validated that the SDR does not yield sub-optimality. An iterated joint secure beamforming algorithm against communication and sensing eavesdroppers is proposed.

What carries the argument

The iterated joint secure beamforming algorithm that alternates between successive convex approximation updates and semidefinite relaxation to solve the secrecy-rate maximization.

If this is right

  • The semidefinite relaxation is tight, so the algorithm returns the globally optimal beamforming vectors.
  • The iterative procedure converges to the maximum achievable secrecy rate under the given constraints.
  • The joint design outperforms separate beamforming of communication and sensing signals in secrecy rate.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same relaxation technique may extend directly to multi-target sensing scenarios without reformulation.
  • Robustness to imperfect channel knowledge at the transmitter could be tested by replacing the nominal channels with uncertainty sets inside the same SCA framework.

Load-bearing premise

The non-convex optimization problem can be reliably solved to global optimality using successive convex approximation, first-order Taylor expansion, and semidefinite relaxation, and that the resulting iterative algorithm converges under the modeled channel and noise conditions.

What would settle it

Compare the secrecy rate returned by the iterative algorithm against the rate obtained by exhaustive search over a low-dimensional beamforming parameter space on the same channel realization; any consistent gap would show that the claimed optimality does not hold.

read the original abstract

Due to great efficiency improvement in resource and hardware space, integrated sensing and communication (ISAC) has gained much attention. In the paper, the physical layer security (PLS) of ISAC system under communication eavesdropper together with sensing eavesdropper is investigated. The system secrecy rate is maximized by transmit beamforming design of communication and sensing signals when taking sensing security, sensing performance and transmit power constraint into consideration. To deal with the formulated non-convex optimization problem, the successive convex approximation (SCA) together with the first-order Taylor expansion and semidefinite relaxation (SDR) is utilized. Additionally, it is theoretically validated that the SDR does not yield sub-optimality in the paper. Thereafter, an iterated joint secure beamforming algorithm against communication and sensing eavesdroppers is proposed. Simulation results validate the effectiveness and advance of the proposed scheme.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The paper examines physical layer security in ISAC systems with both communication and sensing eavesdroppers. It maximizes the secrecy rate via beamforming design for communication and sensing signals, incorporating constraints on sensing security, sensing performance, and transmit power. The approach employs SCA, first-order Taylor expansion, and SDR to handle the non-convex problem, claims theoretical validation that SDR introduces no sub-optimality, proposes an iterative joint secure beamforming algorithm, and uses simulations to demonstrate effectiveness.

Significance. If the theoretical validation and convergence hold, this work would be significant for advancing secure designs in ISAC systems by addressing the dual threat of communication and sensing eavesdroppers, potentially improving resource efficiency and security in integrated systems. The proposal of an iterative algorithm based on standard convex optimization techniques could provide a practical solution, though the absence of detailed proofs and simulation data in the available manuscript limits the ability to confirm its impact.

major comments (2)
  1. [Abstract] The assertion that 'it is theoretically validated that the SDR does not yield sub-optimality' lacks any supporting derivation, conditions, or proof outline, which is central to the optimization approach and requires substantiation to support the claim of global optimality.
  2. [Abstract] No information is provided on the specific formulation of the secrecy rate, the sensing performance metric, or the channel models, making it difficult to evaluate the applicability of the SCA and Taylor approximations used in the iterative algorithm.
minor comments (1)
  1. The abstract could benefit from specifying the exact optimization objective and constraints to enhance clarity for readers.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the constructive comments on our manuscript arXiv:2602.12614. We address each major comment below. Note that only the abstract is available in the provided materials, limiting our ability to quote full sections.

read point-by-point responses

  1. Referee: [Abstract] The assertion that 'it is theoretically validated that the SDR does not yield sub-optimality' lacks any supporting derivation, conditions, or proof outline, which is central to the optimization approach and requires substantiation to support the claim of global optimality.

    Authors: We agree that the abstract does not include the derivation or proof outline. The full manuscript contains a theoretical validation proving that the SDR relaxation yields no sub-optimality, specifically by establishing that an optimal rank-one solution always exists for the original problem under the given secrecy rate and constraint structure. We will revise the abstract to include a brief reference to the conditions and proof or point to the relevant section. revision: yes

  2. Referee: [Abstract] No information is provided on the specific formulation of the secrecy rate, the sensing performance metric, or the channel models, making it difficult to evaluate the applicability of the SCA and Taylor approximations used in the iterative algorithm.

    Authors: The abstract is kept concise by design. The full manuscript defines these elements in the system model and problem formulation. However, since only the abstract is available in this query, we cannot reproduce the exact expressions here. We will ensure the revised introduction provides sufficient context on the secrecy rate (considering both eavesdroppers), sensing metric, and channels to clarify the approximations. revision: partial

standing simulated objections not resolved
  • Exact mathematical expressions for the secrecy rate, sensing performance metric, and channel models, as only the abstract is available in the query.

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The abstract describes a standard non-convex optimization solved via successive convex approximation, first-order Taylor expansion, and semidefinite relaxation, with a claim that SDR introduces no sub-optimality. These are externally established convex-optimization techniques drawn from the broader literature rather than quantities fitted or defined internally to the paper. No equations, self-citations, or parameter-fitting steps are provided in the available text that would allow any reduction of a claimed prediction or uniqueness result to the paper's own inputs by construction. The derivation chain therefore remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract-only access prevents identification of explicit free parameters or invented entities; the work implicitly relies on standard wireless channel and noise models.

axioms (1)
  • domain assumption Standard assumptions on perfect or statistical channel state information and additive Gaussian noise hold for the optimization formulation.
    Typical in physical-layer security papers but not explicitly stated in the abstract.

pith-pipeline@v0.9.0 · 5420 in / 1340 out tokens · 76649 ms · 2026-05-15T22:41:47.197630+00:00 · methodology

discussion (0)

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