Prioritizing data for post-quantum cryptography (PQC)

Quantum computing is fast approaching, and with it comes a serious cybersecurity challenge. The threat of quantum-enabled attacks is real and requires immediate preparation.

This shift is often compared to Y2K, as both involve major updates to critical but largely hidden systems. However, unlike Y2K, there’s no set deadline — quantum risks will emerge gradually. Some, like harvest now, decrypt later attacks, are already happening, making it essential to prioritize action now.

A smart first step in preparing for post-quantum cryptography (PQC) is to identify and prioritize your most sensitive data. Not all data carries equal risk, so focusing on what matters most enables a scalable, risk-based approach to quantum readiness.

Here’s how to build a data prioritization strategy that ensures your most sensitive and valuable assets are protected as the quantum era unfolds.

»Understanding unique risks of sensitive data types

When prioritizing data for post-quantum cryptography, it's not enough to simply know what’s sensitive — you also need to understand why certain data types are more at risk and how they may be uniquely impacted by quantum threats.

Let’s take a closer look at the specific challenges and quantum-era risks associated with each major category of critical data.

»Personally identifiable information (PII)

PII includes names, Social Security numbers, financial records, health data, etc. — information that, if compromised, can lead to identity theft or privacy violations.

»Why it’s challenging

• PII is often widely distributed across internal systems, SaaS platforms, and vendor networks.
• It is subject to strict privacy regulations like GDPR, HIPAA, and CCPA.
• Key identifiers (like SSNs or biometric data) have long lifespans, making them vulnerable to future decryption.

Quantum-specific risk: Attackers may harvest encrypted PII today with the intent of decrypting it years from now using quantum computers — creating long-term exposure even if a breach isn’t immediately damaging.

»Intellectual property (IP)

This category covers trade secrets, proprietary software, patented designs, and research — assets that represent the innovation and competitive edge of a business.

»Why it’s challenging:

• IP is a prime target for espionage, particularly from state-sponsored actors.
• It requires decades-long protection, especially in R&D-heavy industries.
• Encryption practices around internal IP are often inconsistent or underdeveloped.

Quantum-specific risk: Future decryption of stolen IP could lead to competitive disadvantages, lost market share, or strategic disruption — particularly if quantum capabilities are weaponized.

»Financial data

Bank account details, payment credentials, and transaction records must be safeguarded both for customer protection and compliance purposes.

»Why it’s challenging:

• Financial systems operate in real time, where even a short-lived breach can be catastrophic.
• Data moves across a complex ecosystem of institutions, APIs, and fintech platforms.
• Regulatory frameworks require strict auditability and integrity.

Quantum-specific risk: Quantum computing could compromise the digital signatures that authenticate financial transactions, opening the door to fraud or manipulation.

»Government and legal data

This includes national security information, classified records, and sensitive legal documents.

»Why it’s challenging:

• This data typically has very long or indefinite retention periods.
• It is often the focus of geopolitical cyberattacks.
• Systems handling this data are frequently fragmented, mixing legacy and modern infrastructure.

Quantum-specific risk: Compromising this data could have long-term geopolitical consequences — especially if decrypted after being harvested and stored by adversaries.

»Corporate strategic information

This category includes business plans, executive communications, M&A discussions, and other forward-looking strategies.

»Why it’s challenging:

• The value of this data is highly time-sensitive.
• It's often shared widely via cloud collaboration tools, increasing exposure risk.
• It’s frequently undervalued from a security perspective, lacking encryption or access controls.

Quantum-specific risk: If decrypted post-theft, this data could be used for insider trading, market manipulation, or competitive sabotage, even if the breach goes unnoticed for years.

Each data category carries a distinct risk profile in a quantum future. The goal isn’t to treat all data equally, but to align your security investments with the value, lifespan, and vulnerability of the data you hold. By understanding the unique challenges and timelines associated with PII, IP, financial records, legal data, and corporate strategies, organizations can make smarter decisions about what to protect first.

»Classify data based on sensitivity and value

Aligning your data classification tiers with established standards like NIST, ISO/IEC 27001, and regulatory frameworks (such as GDPR or HIPAA) is essential for ensuring consistency, auditability, and long-term interoperability. These standards provide a proven foundation for assessing data sensitivity and risk, making it easier to integrate post-quantum cryptographic strategies into existing security programs. By aligning with these frameworks, organizations can avoid reinventing the wheel, demonstrate due diligence to regulators and stakeholders, and ensure their quantum-readiness efforts are built on a structure that is both industry-recognized and scalable. The recommended tiers are:

• Tier 1 – Highly sensitive: Includes PII, IP, legal, and financial data. These are top priority for quantum-safe encryption.
• Tier 2 – Moderately sensitive: Internal documents, operational records, or customer communications — important, but with lower immediate risk.
• Tier 3 – Low sensitivity: Public-facing or non-sensitive internal data that may not need post-quantum protection in the near term.

»Evaluate data lifespan and retention

Quantum threats aren't just about real-time data breaches — they include the risk of “harvest now, decrypt later” attacks, where attackers collect encrypted data today with the intention of breaking it when quantum computing matures.

• Long-term data: Legal records, compliance archives, and government communications stored for 7–20+ years should be prioritized.
• Short-term data: Session tokens or logs may be lower risk — unless linked to more sensitive systems or workflows.

»Reducing HNDL risk through re-encryption and data hygiene

One of the most effective ways to reduce the long-term risk posed by quantum computing is to regularly re-evaluate and re-encrypt stored data using modern, quantum-resistant algorithms as they become available and validated. Long-retained data, especially sensitive legal, financial, or government records, can remain vulnerable if encrypted with legacy algorithms that are expected to be broken by quantum computers.

Here are several best practices to help mitigate this risk:

• Periodic re-encryption: Implement a lifecycle policy that includes periodic re-encryption of long-lived data. As new cryptographic standards emerge, re-encrypt data using quantum-safe algorithms or hybrid approaches (classical + quantum-safe).
• Key rotation: Rotate encryption keys on a regular basis and use quantum-safe key management. This limits the damage if a single key is compromised or becomes vulnerable to future quantum attacks.
• Data minimization: Regularly audit stored data and securely delete information that is no longer needed. Reducing the amount of long-retained sensitive data directly reduces your attack surface.
• Segmentation by sensitivity and lifespan: Segment stored data based on how long it must remain secure.
• Monitoring and future-proofing: Stay aligned with NIST’s cryptographic guidance as PQC standards continue to evolve. Choose algorithms and tools that support migration paths.

»Securing data in transit and at rest

When preparing for post-quantum threats, it's critical to consider both the data you store and the data you transmit. Quantum computing could allow attackers to decrypt data transiting networks, as well as data that’s been stored for years in cloud systems, databases, or local archives. But it’s not just about protecting data at the physical or digital level; the accessibility of that data is just as important. Here’s how you can address both aspects of quantum security:

»Securing data in transit

Data in transit refers to information moving across networks. This includes emails, API traffic, and online transactions making it essential to secure data in transit with quantum-resistant algorithms. This is especially crucial for communications and financial transactions, where real-time security is paramount.

Key focus areas:

• Emails and messaging: Encrypt email communications with quantum-resistant standards to prevent compromise.
• API traffic and transactions: Protect online payment systems, financial transactions, and business-critical communication from quantum threats by using quantum-safe encryption protocols during data transfer.

»Securing data at rest

Data at rest refers to stored data, whether in cloud systems, databases, or on local servers. For organizations with long-term data retention requirements, the risk of future quantum attacks is high. For example, regulatory archives, historical financial records, and personal health information need to remain secure for years or decades. Quantum-safe encryption is vital to ensure that sensitive data cannot be accessed or decrypted by attackers in the future, even if they manage to steal the data now.

Key focus areas:

• Cloud storage and databases: Ensure all stored data, especially sensitive information (PII, financial records, intellectual property), is encrypted with quantum-resistant algorithms to protect against future quantum decryption capabilities.
• Backup and archive systems: Long-term retention of critical records demands proactive measures to safeguard stored data. Re-encryption or hybrid cryptographic solutions can provide the necessary protection.

»Assessing data exposure and accessibility

The level of data exposure directly impacts the potential damage from quantum attacks. Data that's more accessible is naturally at higher risk.

• Externally exposed data: APIs, public-facing applications, cloud services, and any external systems connected to the internet should be your top priority for quantum-safe encryption. These systems are the first points of entry for attackers and can be targeted in the short term, even if the decryption technology isn't fully mature yet.
• Internal data: While internal data may seem less vulnerable, especially when confined to a private network, it still requires protection. If an internal system is breached, the quantum risk extends to everything stored within it, making it essential to ensure all data in transit within the organization is encrypted with quantum-resistant methods.

When securing both data in transit and at rest, don't just focus on encryption techniques, assess how accessible and exposed your data is across different systems. A comprehensive post-quantum strategy needs to include encryption for both stored and moving data and an evaluation of how vulnerable your data might be, based on where it’s stored, who can access it, and how it's transmitted. By addressing these factors together, you ensure a more robust defense against quantum threats, safeguarding your organization’s most critical data against future attacks.

»Align with regulatory and legal requirements

Many industries are bound by strict compliance rules. Prioritize data subject to:

• Privacy laws: GDPR, HIPAA, and similar frameworks mandate strong data protection.
• Retention rules: Financial records, health data, or government communications often have long legally mandated storage durations.
• National security protocols: Classified or sensitive government data should be among the first to be transitioned.

»Implement hybrid cryptography during transition

We’re not flipping a switch — we’re navigating a phased migration.

• Hybrid solutions: Combine classical and quantum-resistant algorithms during the transition period to mitigate risk without disrupting performance.

• Compatibility testing: Ensure new cryptographic tools work within your existing systems and processes.

Preparing for quantum threats isn’t just a technical challenge — it’s a strategic imperative. By focusing on the sensitivity, lifespan, and exposure of your data, you can make informed decisions about what to protect first. Prioritizing critical information and adopting post-quantum cryptography early helps reduce long-term risk and positions your organization for a secure future. The quantum era may be uncertain in timing, but your readiness doesn’t have to be. Start now, prioritize wisely, and build a resilient foundation that stands the test of time — and technology.

»Final thoughts: Don’t wait for the quantum clock to strike

Quantum computing is not a distant concern, it’s an active risk that’s slowly accelerating toward impact. The shift to post-quantum cryptography is one of the most significant transformations cybersecurity teams will face in the coming decade. But the good news is: it’s manageable with the right strategy.

By classifying data based on sensitivity and retention needs, securing both data in transit and at rest, and aligning with emerging standards and regulations, organizations can take practical steps today to mitigate tomorrow’s threats. Remember, the goal isn’t to quantum-proof everything overnight, it’s to make thoughtful and risk-based decisions that protect your most valuable assets first.

Preparation isn’t just about new encryption algorithms but also includes building the habits, updating infrastructure, and building awareness to adapt to a changing threat landscape. Quantum disruption is coming, but it doesn’t have to catch you off guard.

Start now. Start smart. Secure what matters most. Learn more about how HashiCorp Vault can help secure your data.

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