A Multi-Plane Detection Framework for Quantum-Enabled Cryptographic Attacks: Operationalizing the Detection of Harvest-Now-Decrypt-Later Activity and Attacks on Post-Quantum Cryptography
Kabir G. Kharade, K K.Vengatesan, Hayder Kareem Algabri
The advent of cryptographically relevant quantum computers (CRQCs) poses a fundamental threat to public-key cryptography securing modern digital communications. The most immediate danger is not direct decryption but the harvest-now-decrypt-later (HNDL) attack, wherein adversaries passively collect and archive encrypted traffic today for retrospective decryption once a CRQC becomes operational. This threat is structurally difficult to counter because the collection phase generates no host- or account-level signals detectable by conventional intrusion-detection systems.Simultaneously, migration to NIST-standardized post-quantum cryptography (PQC) specifically ML-KEM (FIPS 203), ML-DSA (FIPS 204), and SLH-DSA (FIPS 205) introduces new vulnerabilities, including chosen-ciphertext side-channel attacks, fault-injection attacks, and protocol downgrade attacks arising during hybrid deployment periods.Existing security tooling addresses cryptographic inventory, encrypted-traffic anomaly detection, and PQC readiness as isolated problems, leaving a critical operational gap. To address this, we propose QCAD (Quantum Cryptographic Attack Detection), a unified multi-plane detection framework integrating four complementary detection planes: (A) flow-metadata behavioral analytics targeting HNDL collection indicators; (B) host- and protocol-level telemetry for PQC implementation flaws and downgrade attacks; (C) continuous crypto-agility monitoring with per-asset Mosca-inequality risk scoring; and (D) quantum-vulnerable deception canaries. These planes feed a unified correlation layer that maps observations to MITRE ATT&CK techniques and produces risk-ranked alerts.Evaluation against synthetic HNDL and PQC-attack benchmarks demonstrates that cross-plane fusion achieves a recall of 0.97 at a 5% false-positive rate (F1 = 0.90, ROC-AUC = 0.99), substantially outperforming any individual plane, confirming that no single observable captures all attack families.A key boundary condition remains: HNDL detection is inherently a probabilistic behavioral-inference problem, and interception occurring on transit infrastructure beyond the defender's perimeter may remain undetectable regardless of sensor deployment.
The advent of cryptographically relevant quantum computers (CRQCs) poses a fundamental threat to public-key cryptography securing modern digital communications. The most immediate danger is not direct decryption but the harvest-now-decrypt-later (HNDL) attack, wherein adversaries passively collect and archive encrypted traffic today for retrospective decryption once a CRQC becomes operational. This threat is structurally difficult to counter because the collection phase generates no host- or account-level signals detectable by conventional intrusion-detection systems.Simultaneously, migration to NIST-standardized post-quantum cryptography (PQC) specifically ML-KEM (FIPS 203), ML-DSA (FIPS 204), and SLH-DSA (FIPS 205) introduces new vulnerabilities, including chosen-ciphertext side-channel attacks, fault-injection attacks, and protocol downgrade attacks arising during hybrid deployment periods.Existing security tooling addresses cryptographic inventory, encrypted-traffic anomaly detection, and PQC readiness as isolated problems, leaving a critical operational gap. To address this, we propose QCAD (Quantum Cryptographic Attack Detection), a unified multi-plane detection framework integrating four complementary detection planes: (A) flow-metadata behavioral analytics targeting HNDL collection indicators; (B) host- and protocol-level telemetry for PQC implementation flaws and downgrade attacks; (C) continuous crypto-agility monitoring with per-asset Mosca-inequality risk scoring; and (D) quantum-vulnerable deception canaries. These planes feed a unified correlation layer that maps observations to MITRE ATT&CK techniques and produces risk-ranked alerts.Evaluation against synthetic HNDL and PQC-attack benchmarks demonstrates that cross-plane fusion achieves a recall of 0.97 at a 5% false-positive rate (F1 = 0.90, ROC-AUC = 0.99), substantially outperforming any individual plane, confirming that no single observable captures all attack families.A key boundary condition remains: HNDL detection is inherently a probabilistic behavioral-inference problem, and interception occurring on transit infrastructure beyond the defender's perimeter may remain undetectable regardless of sensor deployment.
Quantum computers capable of breaking RSA-2048 are projected to emerge by 2030 ± 3 years. Analysis of more than 100 primary sources indicates that 98–100% of healthcare records and 95–100% of government-classified data encrypted today are likely to face retroactive decryption under the Harvest Now, Decrypt Later (HNDL) attack model, in which adversaries collect encrypted data today and decrypt it once cryptographically relevant quantum computers become available. This paper introduces a formal time-dependent risk model that quantifies exposure as a function of data confidentiality lifetime (Ld) and attacker decryption horizon (Ha). Using the vulnerability condition Ld > Ha, we evaluate sector-specific quantum risk across healthcare, finance, government, and cloud environments, demonstrating that long-lived sensitive data faces near-certain compromise under classical public-key cryptography. The study analyzes NIST’s finalized post-quantum cryptography standards (FIPS 203–205: ML-KEM, ML-DSA, and SLH-DSA) and presents a unified five-phase migration framework addressing technical, operational, regulatory, and supply-chain constraints. Drawing on real-world deployments—including Apple iMessage PQ3, Google Chrome, Cloudflare, IBM Quantum Safe, and the U.S. Federal Government—the paper provides actionable guidance for organizations seeking to achieve 90% or greater post-quantum cryptography migration by 2030. The window for protecting long-lived data is now—not when quantum computers arrive.
The arrival of cryptographically relevant quantum computers (CRQCs) represents an existential threat to the public-key cryptographic infrastructure underpinning global enterprise operations. Enterprise security today relies on RSA and elliptic-curve cryptography (ECC) for TLS, VPNs, PKI, code signing, and identity systems—all of which are fundamentally broken by Shor's algorithm on a sufficiently powerful quantum computer. The defining risk is time-shifted compromise: adversaries can harvest encrypted traffic today and decrypt it once CRQCs exist, a threat already underway according to U.S. intelligence assessments. NIST finalized three post-quantum cryptographic (PQC) standards in August 2024 (FIPS 203/204/205) and mandates deprecation of quantum-vulnerable algorithms by 2035. Yet only 5% of organizations have implemented quantum-safe encryption and 95% lack formal quantum transition plans. This paper provides a comprehensive, threat-driven analysis across seven dimensions: quantum algorithm impact, harvest-now-decrypt-later (HNDL) threat models, enterprise asset risks (PKI, TLS, VPNs, code signing, cloud, IoT, identity, blockchain, supply chain), sector-specific vulnerabilities (financial services, healthcare, critical infrastructure), cryptographic primitive analysis, migration standards and roadmaps, and enterprise readiness gaps. The convergence of HNDL attacks already underway, multi-decade data sensitivity windows, and 12–15 year enterprise migration timelines means the migration deadline has, for most sectors, already passed.
Abstract—The advent of fault-tolerant Cryptanalytically Relevant Quantum Computers (CRQCs) presents an existential threat to modern information security. Shor's polynomial-time quantum algorithm renders widely deployed public-key cryptographic primitives—including RSA, Diffie-Hellman (DH), and Elliptic Curve Cryptography (ECDH/ECDSA)—completely vulnerable to private key derivation. Furthermore, 'Harvest Now, Decrypt Later' (HNDL) adversarial campaigns actively intercept and store encrypted enterprise telemetry today, anticipating future quantum decryption capabilities. In response, the National Institute of Standards and Technology (NIST) finalized its primary Post-Quantum Cryptography (PQC) standards in FIPS 203 (ML-KEM), FIPS 204 (ML-DSA), and FIPS 205 (SLH-DSA). However, transitioning complex enterprise IT ecosystems to quantum-resistant primitives introduces severe architectural and computational disruptions: public key and signature sizes increase by several orders of magnitude, cryptographic handshake latencies escalate, network packets experience Maximum Transmission Unit (MTU) fragmentation, and legacy Hardware Security Modules (HSMs) lack microarchitectural support for lattice-based polynomial arithmetic. This paper provides an exhaustive, mathematically grounded technical survey and architectural roadmap for enterprise PQC migration. We formalize the Module Learning with Errors (M-LWE) and Module Short Integer Solution (M-SIS) hardness foundations, evaluate hybrid classical/post-quantum cryptographic transition models across standard transport protocols (TLS 1.3, IKEv2/IPsec, SSH), and formulate an enterprise Crypto-Agility Maturity Model. Furthermore, we construct an empirical enterprise testbed measuring throughput, connection establishment latency, memory footprints, and packet fragmentation across legacy and quantum-resistant suites. Our results show that while ML-KEM-768 achieves microsecond-level encapsulation, its 1,088-byte ciphertext expands TLS ClientHello payloads into multiple TCP segments under constrained networks. Finally, we establish open research directions in post-quantum identity federations, stateful hash signature tracking, and hardware-accelerated polynomial arithmetic. Index Terms—Post-Quantum Cryptography (PQC), FIPS 203 (ML-KEM), FIPS 204 (ML-DSA), Crypto-Agility, TLS 1.3, Lattice-Based Cryptography, Harvest Now Decrypt Later, Hardware Security Modules (HSM), Enterprise Migration.
The simultaneous maturation of quantum computing and artificial intelligence represents a defining inflection point for the security of digital civilization. This chapter examines the convergence of these two transformative forces through a bidirectional analytical lens: how artificial intelligence can accelerate and improve the organizational transition to post-quantum cryptography and how post-quantum cryptographic standards must be applied to secure AI infrastructure itself. Building on the NIST finalization of FIPS 203 (ML-KEM), FIPS 204 (ML-DSA), and FIPS 205 (SLH-DSA) in August 2024 and the subsequent selection of HQC in March 2025, the chapter develops a practitioner-oriented treatment of the algorithmic foundations, performance characteristics, and deployment realities of each standardized scheme. A dedicated section develops the “Harvest Now, Decrypt Later” (HNDL) threat as a present-tense security emergency rather than a future concern and introduces a novel detection architecture that integrates HNDL behavioral indicators into the streaming telemetry pipeline of Chapter 2 and the AI-SOC framework of Chapter 4 . The chapter examines AI-assisted cryptographic discovery, inventory automation, side-channel vulnerability detection, and migration workflow orchestration as tools for managing the organizational complexity of the PQC transition. It addresses the reciprocal challenge of applying PQC to AI infrastructure itself – securing large language model inference pipelines, federated learning gradient exchanges, agentic communication channels, and model provenance attestation against quantum-capable adversaries. A practical deployment section documents the installation and operation of the Open Quantum Safe liboqs library and OQS-OpenSSL provider on Ubuntu 24.04 LTS, with original step-by-step guidance derived from direct implementation experience. The chapter closes by synthesizing the governance requirements, policy timelines, and organizational frameworks that responsible PQC transition demands – and by tying together the 11-chapter arc of this book into a single coherent argument about what secure looks like in the age of autonomous defense.
As quantum computing technology transitions from theoretical frameworks to scalable physical implementations, the "Harvest Now, Decrypt Later" (HNDL) strategy has emerged as a primary existential threat to long-term digital security. Adversaries are currently intercepting and archiving encrypted sensitive data with the intent of performing retroactive cryptanalysis once cryptographically relevant quantum computers (CRQC) become available. This paper addresses the vulnerability of current Public Key Infrastructure (PKI), specifically RSA and Elliptic Curve Cryptography (ECC), which are susceptible to Shor’s algorithm. We propose "Aethelgard," a high-performance hybrid cryptographic framework that nests NIST-standardized Post-Quantum Cryptography (PQC), specifically ML-KEM (Kyber), within established classical key exchange protocols. By utilizing a dual-layered Key Encapsulation Mechanism (KEM), our framework ensures that data remains confidential even if one of the underlying mathematical primitives is compromised. We evaluate the framework’s efficacy through rigorous network simulations, measuring computational overhead, handshake latency, and packet fragmentation across diverse traffic profiles. Experimental results indicate that while the hybrid approach increases the public key size to approximately 1.2 KB, the overall handshake latency increases by a manageable 18% compared to classical-only protocols. This research demonstrates that hybridizing cryptographic primitives is the most viable path toward achieving immediate "crypto-agility" and mitigating the silent threat of HNDL without sacrificing the reliability of current production environments.
The imminent advent of a Cryptographically Relevant Quantum Computer (CRQC) poses an existential threat to the US financial infrastructure.Current payment rails including FedWire, CHIPS, and ACH rely on RSA and ECC standards that are mathematically vulnerable to Shor's Algorithm.This facilitates "Harvest Now, Decrypt Later" (HNDL) attacks, where encrypted data is intercepted today for future decryption.This paper evaluates the migration to NIST-standardized Post-Quantum Cryptography (PQC), specifically ML-KEM and ML-DSA.We analyze the architectural challenges of integrati ng these primitives into ISO 20022 formats, focusing on the trade-offs between increased packet size and sub-millisecond latency requirements.By proposing a phased migration framework using Hybrid Cryptographic Wrappers, this research provides a roadmap for maintaining regulatory compliance under NSM-10 while preventing a systemic collapse of digital trust and the associated multitrillion-dollar risk to the US GDP.