When quantum computers become generally available, they’ll be able to crack current public-key cryptographic algorithms, putting digitally stored and transmitted data at risk. But the threat already exists, as attackers use the "harvest now, decrypt later" tactic. Discover why building a comprehensive cryptographic inventory and executing a phased operational strategy are critical for protecting your data against quantum computing attacks.

The quantum threat to modern security architecture

Future quantum computers will represent a threat to the foundational security architecture that protects digital data. 

For decades, the global economy, national security apparatus, and critical infrastructure have relied on asymmetric cryptography, specifically RSA and elliptic curve cryptography (ECC), to secure data in transit, authenticate identities, and protect digital signatures. The mathematical difficulty of factoring large integers or solving discrete logarithm problems has long provided a robust shield against cyber attacks launched using conventional computing capabilities.

However, the rapid maturation of quantum computing represents an existential threat to these algorithms. A fully fault-tolerant, cryptographically relevant quantum computer (CRQC) capable of instantly shattering current encryption standards is still several years away. However, organizations need to migrate to quantum-resistant algorithms now. The reason? Adversaries are using "harvest now, decrypt later" (HNDL) tactics. They steal data encrypted with algorithms vulnerable to quantum computing attacks, and save it, hoping to decrypt it in the future once quantum capabilities mature.

The impact of Executive Order 14412

Recognizing the immediacy of this threat, regulatory agencies have responded accordingly. The White House recently issued Executive Order 14412, “Securing the Nation Against Advanced Cryptographic Attacks,” which mandates that executive-branch federal agencies pay immediate operational and engineering attention to post-quantum cryptography (PQC) readiness.

This directive introduces critical pillars that redefine enterprise security strategies:

• Accelerated migration timelines: Moving aggressively ahead of prior federal benchmarks, the EO sets a deadline of Dec. 31, 2030, for transitioning high-value assets to PQC for key establishment, and Dec. 31, 2031, for digital signatures. 
• Supply chain and contractor mandates: The EO directs the Federal Acquisition Regulatory (FAR) Council to require covered federal contractors to meet strict post-quantum Federal Information Processing Standards (FIPS) from the National Institute of Standards and Technology (NIST) by the end of 2030.
• Cryptographic weakness as an active vulnerability: In a significant shift for vulnerability management, contractors’ vulnerability disclosure programs (VDPs) must explicitly treat the absence of encryption or the use of non-FIPS-approved algorithms as reportable cryptographic vulnerabilities, effectively redefining crypto-hygiene from a passive audit finding to an active risk-mitigation item.
• The mandate for cryptographic bills of materials (CBOMs): To achieve the complete visibility required for this transition, current and forthcoming frameworks, like CycloneDX, emphasize automated discovery of cryptographic assets across all software, firmware, and hardware dependencies.

In this high-stakes regulatory environment, visibility has emerged as the primary currency of defense. Organizations cannot migrate what they cannot see. Consequently, governments and regulatory bodies worldwide, from the White House and the U.S. National Security Agency (NSA) to the European Union and the Monetary Authority of Singapore, have synchronized their directives around a single, non-negotiable requirement: the establishment of a comprehensive cryptographic inventory. Organizations must identify, catalog, and assess every cryptographic asset within their environment to facilitate an orderly transition to PQC.

The collapse of asymmetric cryptography

Current public-key infrastructure (PKI) relies on the computational intractability of specific mathematical problems. RSA encryption relies on the difficulty of integer factorization, while Diffie-Hellman and ECC rely on the discrete logarithm problem. It would take billions of years for a classical supercomputer to crack a 2048-bit RSA key. 

Quantum computers utilize qubits, which can exist in a state of superposition, representing both 0 and 1 simultaneously. This property, combined with quantum entanglement, allows for massive parallelism in calculation. 

In 1994, mathematician Peter Shor developed Shor’s Algorithm, which theoretically demonstrated that a quantum computer with sufficiently stable qubits could solve both integer factorization and discrete logarithm problems in polynomial time versus problems in exponential time on a classical computer. In other words, a problem that would take an impossibly long time for any real-world computer problem to solve can now be solved in a usefully short amount of time.

The implications are catastrophic for current standards:

• RSA-2048 and RSA-4096: Completely broken.
• Elliptic-curve Diffie–Hellman (ECDH) and Elliptic Curve Digital Signature Algorithm (ECDSA): Completely broken.
• Diffie-Hellman: Completely broken.

Symmetric encryption, like AES-256, is more resilient; Grover’s Algorithm effectively halves the key strength, meaning AES-128 provides only 64 bits of security, but AES-256 remains secure against quantum attacks. Therefore, the immediate crisis is concentrated in asymmetric cryptography used for key exchange, such as TLS/SSL handshakes and SSH session negotiation, as well as for digital signatures (authentication, code signing).

The "harvest now, decrypt later" strategy

The most pervasive misconception regarding PQC is that organizations have until Q-Day, the day a CRQC comes online, to upgrade their systems. This view ignores the “harvest now, decrypt later” attack vector, which has fundamentally shifted the risk timeline from the future to the present.

In an HNDL attack, sophisticated adversaries, primarily nation-states and well-funded criminal syndicates, intercept encrypted traffic today. At scale, this harvesting is primarily executed by nation-states utilizing Border Gateway Protocol (BGP) route manipulations to hijack large volumes of data in transit, alongside the exfiltration and theft of whole encrypted databases during network intrusions. While attackers cannot currently read this data, they store it in massive data centers, effectively time-capsuling the information. The moment a quantum computer capable of running Shor’s Algorithm becomes available, they will then decrypt this harvested data.

Operationalizing the migration: A phased strategy

Implementing the right tools is only the first step. Organizations need a coherent operational strategy to navigate the migration. Based on NIST SP 1800-38 and CISA guidance, the following phased approach is recommended.

Phase 1: Automated discovery: Establish the baseline. You cannot fix what you do not know exists. Within environments, discovery goes a step further than reading configurations: Organizations should inventory resources from the connected accounts and actively scan their internet-facing services to capture the key exchanges and ciphers these services negotiate. Because HDNL targets data in transit, this outside-in view pinpoints the exposed cloud services most at risk and folds them directly into your exposure management workflow.

Phase 2: Prioritization and risk assessment: Not every server needs PQC today. Identify systems with the highest risk and the most critical data.

Phase 3: Remediation and crypto-agility: Upgrade systems to hybrid — meaning, running in parallel both conventional cryptography and PQC — and, finally, fully PQC compliant. Governmental mandates generally have set the year 2035 for complete quantum resistance for all systems. Avoid hard-coding the new algorithms. Use configurations that allow you to swap algorithms easily. The PQC standards are new; if a vulnerability is found next year in one of the new PQC standards, you must be able to switch to an alternative without recompiling code.

Phase 4: Continuous verification: Prevent regression by making regular compliance assessments. A system might be compliant today, but a DevOps push next week might overwrite the config file and revert it to RSA-only. Continuous scanning ensures you maintain the quantum safe state over time.

How can Tenable help?

Closing the gap on HNDL starts with treating cryptographic risk as just another exposure to manage, not a separate audit exercise.

Bring SSL/TLS and SSH protocol visibility across your cloud and IT infrastructure into the Tenable One Exposure Management Platform's workflow you use to track vulnerabilities, misconfigurations, and identity risk. That way, cryptographic weaknesses surface alongside everything else competing for your team’s attention, instead of living in a separate report.

That visibility comes together in Tenable One’s Cryptographic Inventory view, which shows where cryptographic risk lives across your environment: Which services still rely on classical, quantum-vulnerable ciphers, and which have already moved to post-quantum protection. Widgets summarize your overall cryptographic posture at a glance, so quantum readiness becomes one more metric in your exposure picture.

What the cryptographic inventory view surfaces:

• Services using PQC: Reports on services equipped with at least one post-quantum cipher. It will specify which post-quantum ciphers were discovered, reporting by port and protocol.
• Services not using PQC: Reports on services that support no post-quantum ciphers.
• Cipher inventory: View an asset JSON-based inventory by service and cipher.
• TLS and SSH weaknesses: View plugins that have detected weaknesses in conventional-computing algorithms.
• Certificate expiry and configuration concerns: See certificates that have expired or are soon to expire, as well as configuration concerns such as self-signed certificates.

Users can drill down into specific assets to see the JSON-based Cryptographic Inventory and use the Tenable Asset Criticality Rating (ACR) to help with prioritization of systems for remediation. ACR assesses factors like device function, connectivity, and third-party data. Assets with higher ACR (e.g., 6–10) are more critical to your business.
 

^{Post-quantum cipher analysis dashboard in the Tenable One Exposure Management Platform}

The time for action is now

Tenable’s introduction of the set of Cryptographic Inventory dashboards and plugins represents a critical evolution in vulnerability management. It provides the data foundation necessary for the PQC transition. It empowers organizations to answer the regulator’s question, “Are you quantum ready?”, with data, precision, and confidence. The quantum era is arriving. With the right visibility, organizations can ensure their security arrives with it.