Insider Threats in the Age of Post-Quantum Cryptography

The race to adopt post quantum cryptography (PQC) is one of the most important security transitions of our time. Quantum computers, once they reach sufficient scale, will be able to break much of the encryption that protects today’s digital world. Governments, enterprises, and critical infrastructure providers are already preparing for this shift. Yet amid the urgency to upgrade, one risk often gets overlooked: insiders.

While most discussions around PQC focus on external adversaries and algorithm strength, the reality is that someone inside the company could quietly install a backdoor during the migration process. This is not a hypothetical concern. Insider threats have shaped cybersecurity history, and PQC migration creates new opportunities for them to resurface.

 

Why PQC Migration Is a Prime Target

Migrating to PQC is not a simple patch. It is a sweeping overhaul of cryptographic infrastructure. Organizations must:

• Select new algorithms from NIST’s ongoing standardization process (NIST, 2022).
• Rewrite or replace code libraries.
• Update protocols and key management systems.
• Integrate PQC with legacy systems that may not have been designed for quantum-safe operations.

Each of these steps introduces complexity. Complexity, in turn, creates opportunities for insiders to manipulate systems in ways that are difficult to detect. Unlike external attackers, insiders already have access, trust, and knowledge of the company’s systems. That combination makes them uniquely dangerous.

 

How an Insider Could Plant a Backdoor

There are several plausible attack vectors insiders could exploit during PQC migration:

1. Algorithm Selection

An insider could advocate for weaker or less vetted algorithms. For example, if a company chooses an algorithm that has not yet been fully standardized or widely tested, the insider could exploit known weaknesses. This is especially risky because PQC algorithms are still relatively new, and the cryptographic community is actively discovering potential flaws.

2. Implementation Vulnerabilities

Even strong algorithms can be undermined by poor coding practices. An insider could deliberately introduce insecure random number generators, side-channel leaks, or subtle bugs that weaken the system. Cryptography history is full of examples where implementation flaws, not the math itself, created vulnerabilities (Schneier, 2015).

3. Supply Chain Manipulation

If PQC libraries are sourced externally, insiders could tamper with dependencies or package managers. The SolarWinds breach showed how supply chain compromises can ripple across industries (CISA, 2021). During PQC migration, a malicious insider could insert backdoors into third-party libraries before they are integrated.

4. Configuration Sabotage

Cryptographic strength depends on correct configuration. An insider could misconfigure key management systems, disable certificate validation, or set insecure defaults. These changes might look like routine updates but could create hidden access points.

 

Real-World Parallels

While PQC migration is new, insider threats are not. Edward Snowden’s disclosures highlighted how insiders can exploit privileged access to compromise systems (Greenberg, 2019). Other cases, such as the theft of trade secrets by employees in the semiconductor industry, show that insiders often act during periods of technological transition when oversight is stretched thin.

The lesson is clear: PQC migration simply adds new layers of complexity that insiders can exploit.

 

Why Detection Is So Difficult

Insider backdoors are notoriously hard to detect. They often masquerade as legitimate code changes or configuration updates. Traditional monitoring tools focus on external threats, not subtle manipulations from trusted employees. Even code reviews can miss cleverly hidden vulnerabilities if reviewers lack deep cryptographic expertise.

Research from Carnegie Mellon’s Software Engineering Institute shows that insider incidents often go undetected for months or even years because organizations underestimate the risk (SEI, 2020). During PQC migration, this blind spot could be catastrophic. By the time a backdoor is discovered, quantum-safe systems may already be compromised.

 

Mitigation Strategies

Organizations can reduce insider risks during PQC transitions by adopting layered defenses:

• Rigorous code review: Require multiple reviewers with cryptographic expertise for all PQC related changes.
• Supply chain validation: Verify the integrity of external libraries and dependencies through reproducible builds and cryptographic signatures.
• Access controls: Limit who can make changes to cryptographic systems and enforce separation of duties.
• Continuous monitoring: Use anomaly detection to flag unusual code commits, configuration changes, or access patterns.
• Culture of security: Encourage transparency and accountability. Insiders are less likely to act maliciously in environments with strong ethical norms and oversight.
• Red team exercises: Simulate insider attacks during PQC migration to test detection and response capabilities.

 

The Bigger Picture

Quantum computing is often portrayed as the external boogeyman that will break today’s encryption. But the insider threat is just as real and arguably more immediate. As companies prepare for PQC, they must remember that the most dangerous adversary may already be inside the building.

The lesson is clear: PQC migration is not just a technical upgrade. It is a human and organizational challenge. Without strong insider threat defenses, even the most advanced quantum-safe algorithms can be rendered useless.

 

Conclusion

The transition to post-quantum cryptography is one of the most significant security challenges of the 21st century. It is not enough to focus on algorithm strength or external adversaries. Organizations must also recognize that insiders can exploit the migration process to install backdoors.

By combining technical safeguards with cultural and organizational defenses, companies can reduce the risk. PQC migration should be treated not only as a cryptographic upgrade but as a holistic security transformation. Only then can organizations truly prepare for the quantum future.

 

Sources

• NIST. “Post-Quantum Cryptography Standardization.” https://csrc.nist.gov/projects/post-quantum-cryptography
• Schneier, Bruce. Applied Cryptography. Wiley, 2015.
• CISA. “Supply Chain Compromise: SolarWinds Incident.” https://www.cisa.gov/news-events/alerts/2021/01/06/supply-chain-compromise
• Greenberg, Andy. Sandworm: A New Era of Cyberwar and the Hunt for the Kremlin’s Most Dangerous Hackers. Doubleday, 2019.
• Carnegie Mellon Software Engineering Institute. “Insider Threats in Cybersecurity.” https://resources.sei.cmu.edu/library/asset-view.cfm?assetid=653253