Navigating the Quantum Horizon: A Multi-Surface Framework for Post-Quantum TLS Observability

      In an increasingly digital world, the security of our online communications hinges on robust encryption. Transport Layer Security (TLS), the cryptographic protocol underlying secure internet connections, is the bedrock of this trust. However, with the looming threat of quantum computing, the very foundations of current cryptographic standards are being challenged. The transition to Post-Quantum Cryptography (PQC) is no longer a distant theoretical exercise but an urgent operational imperative for enterprises globally.

      This shift introduces significant complexities, particularly in accurately assessing an organization's readiness for the quantum era. A recent academic paper, "Observability for Post-Quantum TLS Readiness: A Multi-Surface Evidence Framework" by José Luis Delgado (Source: arXiv:2605.02978), delves into these challenges, proposing a comprehensive framework to ensure reliable measurement and verification of PQC readiness within TLS environments.

The Quantum Threat to Current Encryption

      Current public-key cryptography, like RSA and elliptic-curve cryptography (ECC), relies on mathematical problems that are computationally infeasible for classical computers to solve within a practical timeframe. However, quantum computers, once fully realized, could efficiently break these cryptographic schemes, rendering today's secure communications vulnerable. This is why the National Institute of Standards and Technology (NIST) has been standardizing new PQC algorithms, such as ML-KEM for key encapsulation and ML-DSA/SLH-DSA for digital signatures.

      To mitigate this risk, the TLS ecosystem is actively developing and deploying "hybrid key-establishment" mechanisms. These solutions combine classical cryptographic methods with new PQC algorithms, offering a dual layer of protection. If one algorithm is compromised, the other still provides security. For example, variants like X25519MLKEM768 are being integrated into TLS 1.3 to ensure forward secrecy against both classical and quantum attacks. For organizations managing sensitive data, understanding and implementing these hybrid solutions is paramount to future-proofing their security posture.

Challenges in Assessing Post-Quantum TLS Readiness

      Measuring an organization's PQC readiness is not straightforward. TLS, especially TLS 1.3, is designed for privacy and encrypts a significant portion of the handshake, making traditional packet inspection difficult. This protocol opacity means that simply observing network traffic may not reveal the full picture of an endpoint's cryptographic capabilities. Factors like session resumption, HelloRetryRequest, mutual TLS (mTLS), and various network optimizations (truncation, fragmentation, coalescing) further complicate accurate assessment. Even the certificates, which typically declare cryptographic capabilities, are often encrypted in TLS 1.3 sessions, making them inaccessible to passive observation.

      Consider a scenario where a server supports a hybrid PQC group, but a client defaults to negotiating a classical group. A passive observation would only show the classical negotiation, masking the server's PQC capability. Furthermore, actively probing an endpoint provides a snapshot of its current capability, but this might not perfectly align with what was negotiated in a past or ongoing session, especially if configurations drift over time. This highlights the need for a more sophisticated approach that accounts for these "seams between observation and inference," ensuring that all available evidence is systematically gathered and interpreted.

Introducing the Multi-Surface Evidence Framework

      To address these complexities, the paper proposes a "multi-surface evidence framework." This innovative approach separates evidence into four distinct "surfaces" and maps these observations onto seven "measurement planes" to provide a holistic view of TLS readiness.

      The four evidence surfaces are:

• Passive Session Evidence (Σ 𝑃 ): Data collected from monitoring live network traffic, such as packet captures.
• Active Probe Evidence (Σ 𝐴 ): Information gathered by actively initiating connections to endpoints and observing their responses, revealing their capabilities.
• Certificate-Chain Evidence (Σ 𝐶 ): Cryptographic details extracted from the digital certificates presented by servers, including their public keys and signature algorithms.
• Registry/Rule Evidence (Σ 𝑅 ): Knowledge derived from public standards, cryptographic registries, and predefined inference rules (e.g., NIST PQC standards, TLS protocol specifications).

      These surfaces are then projected onto seven measurement planes:

• Session Plane: Details of an individual TLS connection.
• Key Establishment Plane: How cryptographic keys are securely exchanged.
• Capability Plane: The full range of cryptographic algorithms an endpoint supports.
• Authentication Plane: How identities are verified (e.g., via certificates).
• Lifecycle Plane: The validity and revocation status of certificates.
• Observability Plane: The limitations and possibilities of gathering evidence.
• Policy Plane: Whether the observed configurations align with organizational security policies.

      By combining evidence from these diverse sources, the framework constructs a "measurement object" that explicitly tracks the provenance of each piece of information, highlighting any ambiguities or contradictions. This meticulous approach ensures that conclusions about PQC readiness are based on verifiable data, not assumptions.

Practical Implementation and Evaluation

      The research instantiates this framework as a reproducible artifact, leveraging JSON Schemas for rigorous data definition across scenarios, observations, ground truth, and inferred results. It includes versioned registries for TLS groups, signature schemes, and X.509 OIDs, alongside auditable inference rules and stress contracts.

      The framework was evaluated through two key settings:

      1. Controlled Benchmark (PQ-TLS Observability Benchmark v1): This benchmark included 29 controlled scenarios, covering various TLS versions (1.2, 1.3), classical and hybrid key establishments, mTLS, resumption, HelloRetryRequest (HRR), network conditions (truncation, fragmentation, coalescing), temporal drift, IPv6, and certificate chain depth variations. These scenarios included both "canonical" cases with clear expected outcomes and "stress" scenarios designed to produce ambiguity or incomplete information.

      2. Stratified Public Campaign: The framework was tested against over 1000 public targets with 2000 fresh probes, alongside a comparison against existing scanners like SSLyze and testssl.sh.

Key Findings and Business Implications

      The evaluation yielded critical insights into the limitations of traditional assessment methods and the power of a multi-surface approach:

• Baseline Inadequacy: A baseline TLS quantum-vulnerability analyzer, relying primarily on passive packet inspection, detected only 2 out of 29 controlled runs, and critically, 0 out of 23 TLS 1.3 runs. This starkly demonstrates that single-surface, especially passive-only, methods are insufficient for modern TLS 1.3 environments where much of the cryptographic handshake is encrypted.
• Multi-Surface Superiority: The multi-surface framework achieved broad closure across all measurement planes, even in complex scenarios. For example, in the public campaign, it confirmed hybrid capability for 310 targets, identifying instances where endpoint capability exceeded what any single classical session view could reveal.
• Detection of Drift: Repeated rounds of the public campaign showed high stability in confirmed hybrid capabilities, but also exposed small, yet significant, temporal drift in endpoint capabilities and certificate information. This highlights the need for continuous monitoring.
• Explicit Uncertainty Handling: The framework's design inherently preserves uncertainty, surfaces contradictions, and correctly reports "unknown" or "not\_applicable" when evidence is truly lacking. This is crucial for avoiding false positives or a misleading sense of security.

      For enterprises, these findings translate directly into business outcomes:

• Reduced Risk: By accurately identifying PQC readiness and detecting vulnerabilities, organizations can proactively mitigate the risk of future quantum attacks. This is vital for sectors handling long-lived sensitive data such as financial services, healthcare, and government.
• Enhanced Compliance: A robust observability framework ensures compliance with evolving PQC standards and regulatory requirements, avoiding potential penalties and reputational damage.
• Optimized Deployment: Understanding true endpoint capabilities allows for more efficient and targeted PQC migration strategies, reducing unnecessary expenditures on redundant or misaligned security implementations.

Operational Guidance for Crypto-Agility Auditing

      The research provides clear operational guidance for organizations embarking on crypto-agility auditing:

• Passive evidence is effective for closing session-level measurement planes. For instance, observing the cipher suite actually negotiated.
• Active corroboration is indispensable for establishing endpoint capability lower bounds, especially for encrypted TLS 1.3 handshakes. An AI Box Series, deployed at the edge, could provide localized, active probing capabilities without cloud dependency, enhancing privacy and reducing latency for such assessments.
• Certificate-chain evidence, often collected through active retrieval, is essential for closing authentication and lifecycle planes, verifying the cryptographic material and validity of digital identities.
• Uncertainty and contradiction must be treated as first-class measurement outputs. Instead of forcing an answer, a sound framework acknowledges when information is incomplete or conflicting. Tools leveraging AI Video Analytics could be adapted to not just detect anomalies but to highlight data gaps and ambiguities in network security posture.

      ARSA Technology, experienced since 2018 in delivering practical AI and IoT solutions, understands the importance of robust observability and secure infrastructure. Our focus on privacy-by-design and flexible deployment models positions us to assist enterprises in navigating complex security challenges, including the evolving landscape of post-quantum cryptography. We offer ARSA's diverse product portfolio, designed to provide the intelligence and control needed for mission-critical operations.

      As the quantum threat advances, a piecemeal approach to TLS security will no longer suffice. Adopting a multi-surface evidence framework is a strategic imperative for any enterprise committed to maintaining a resilient and future-proof digital infrastructure.

      To explore how ARSA Technology can support your journey towards post-quantum readiness and enhance your security observability, we invite you to contact ARSA for a free consultation.

      Source: Delgado, J. L. (2026). Observability for Post-Quantum TLS Readiness: A Multi-Surface Evidence Framework. arXiv preprint arXiv:2605.02978.