But that protection is not permanent. The same mathematical foundations that make today’s public-key cryptography strong can, in time, become its weakness, because quantum computing changes what is computationally feasible.
For intelligence and defence agencies it’s a strategic one. Whoever gains quantum-enabled cryptanalytic capability first could decrypt adversarial communications, expose hidden networks, and extract insights from data that would otherwise remain sealed for decades.
That’s why governments are preparing now, not only to defend against future quantum attacks, but to understand the offensive implications and the shifting balance of power that comes with them.
Case: Cryptanalysis and codebreaking with quantum computing
Many of today’s most widely used cryptographic protocols depend on problems that are extremely hard for classical computers to solve at scale, such as integer factorisation (used by RSA) and the discrete logarithm problem (used by ECC).
A sufficiently capable, fault-tolerant quantum computer could solve these problems far more efficiently, making it possible to break RSA and ECC-based protections that secure:
- encrypted state and military communications
- VPNs, secure web traffic, and authentication systems
- key exchange protocols underpinning digital infrastructure
- stored encrypted archives (including sensitive historical data)
This creates a dual risk that governments must take seriously:
- “Harvest now, decrypt later”: adversaries can collect encrypted traffic today and decrypt it in the future once quantum capability matures.
- Cryptographic shock: if quantum codebreaking becomes practical faster than expected, legacy systems could become unsafe with limited time to migrate.
In this context, quantum cryptanalysis is a forcing function: it accelerates the need to modernise cryptography, upgrade key management, and adopt quantum-resilient security architectures across the public sector.
Business value
- Strategic advantage in intelligence operations: Quantum-enabled cryptanalysis could unlock high-value adversarial communications and accelerate insight extraction in time-critical missions.
- Clearer visibility into national cryptographic vulnerabilities: Understanding what quantum attacks could break helps governments prioritise upgrades across infrastructure, procurement, and classified systems.
- Faster development of quantum-resilient protocols: Preparing for the threat drives the adoption of post-quantum cryptography, crypto-agility, and security-by-design in new government services.
- Stronger national cybersecurity posture: Early migration reduces exposure to long-term data compromise and supports resilience across defence, diplomacy, energy, mobility, and citizen-facing systems.
Technology readiness
Quantum cryptanalysis that meaningfully threatens RSA and ECC at scale requires fault-tolerant quantum computers, hardware with enough stable qubits and robust error correction to run large, complex algorithms reliably. That level of capability is still in the research and experimental phase.
But the strategic reality is that migration timelines are long. Government systems are complex, procurement cycles are multi-year, and cryptography is deeply embedded. Waiting for a “quantum breakthrough headline” is the wrong trigger. The practical trigger is: how long it takes to upgrade everything that matters.
Near-term action focuses on:
- crypto-agility (systems that can swap algorithms without redesign)
- inventorying where RSA/ECC are used across agencies and suppliers
- piloting and rolling out post-quantum cryptography
- strengthening key management, identity, and long-term data protection policies
Leading players and experiments
NSA and GCHQ are researching quantum-era cryptographic risks and the implications for intelligence and national security.
IBM and Google continue to advance quantum processors and tooling that support experiments relevant to cryptographic workloads.
SandboxAQ is exploring quantum security applications, including approaches that help organisations transition to quantum-resilient systems.
Discover more use cases here
