"Post-Quantum Cryptography is necessary - but it is not a simple upgrade"

The challenges are not limited to algorithms. They span technology, operations, ecosystems, and governance. Understanding these challenges is critical for a successful transition.

Challenges in Adopting Post-Quantum Cryptography

Cryptographic & Algorithmic Challenges

PQC algorithms are fundamentally different from RSA and ECC. Key challenges include:

  • Significantly larger public keys and signatures

  • Higher memory usage

  • Different performance trade-offs

  • Some algorithms being stateful or complex to implement securely

Unlike mature RSA/ECC libraries, PQC implementations are still evolving.

"PQC algorithms are standardized, but large-scale operational experience is still growing"

Performance & Scalability Challenges

Larger cryptographic artifacts impact performance in unexpected ways:

Network Impact

  • Larger TLS handshakes

  • Increased latency on high-traffic systems

  • Higher bandwidth usage

Compute Impact

  • More CPU cycles for signature verification

  • Increased memory pressure

  • Potential bottlenecks in HSM-backed operations

Storage Impact

  • Faster growth of certificate databases

  • Larger logs and audit trails

  • Expanded archival storage for long-term validation

"PQC performance issues rarely appear in isolation - they cascade across systems"

PKI Infrastructure Challenges

PKI systems were designed around RSA and ECC assumptions. Challenges include:

  • CA software tightly coupled to classical algorithms

  • OCSP and CRL size growth

  • Timestamping services producing larger tokens

  • Increased load on validation endpoints

Long-lived PKI components are especially difficult to upgrade without service disruption.

"Stability and longevity are PKI’s strengths but also make migration harder"

HSM and Hardware Limitations

Many Hardware Security Modules:

  • Have limited or no PQC support

  • Are optimized for small-key RSA/ECC operations

  • May struggle with large PQC key sizes

Firmware updates, certification cycles, and vendor roadmaps further complicate adoption.

"Migration Is a Program, Not a Patch"

Ecosystem and Compatibility Challenges

PQC requires broad ecosystem support:

  • Operating systems

  • Browsers

  • Load balancers

  • Network appliances

  • Middleware and libraries

Partial adoption creates:

  • Interoperability failures

  • Fallback risks

  • Operational complexity

"Crypto Is Only as Strong as Its Weakest Link"

Security & Implementation Risks

New cryptography introduces new risks:

  • Immature implementations

  • Side-channel vulnerabilities

  • Incorrect parameter selection

  • Incomplete validation logic

These risks are highest in:

  • Custom implementations

  • Embedded systems

  • Performance-optimized code paths

New Crypto ≠ Risk-Free Crypto

"PQC removes quantum risk but introduces engineering risk if poorly implemented"

Operational Reality: Migration Takes Time

Real-world PQC adoption involves:

  • Crypto inventory and discovery

  • Parallel classical + PQC operation

  • Long transition periods

  • Staff training and tooling updates

Rushed transitions increase the risk of:

  • Outages

  • Trust failures

  • Compliance violations

"PQC removes quantum risk but introduces engineering risk if poorly implemented"

What These Challenges Mean

  • PQC adoption is unavoidable

  • The transition is complex but manageable

  • Early planning reduces risk

  • Crypto agility is the most valuable capability

FAQ

Why is adopting Post-Quantum Cryptography more than just replacing algorithms?

Post-Quantum Cryptography impacts the entire cryptographic lifecycle, not just algorithms. PQC introduces significantly larger keys and signatures, which affect certificate sizes, TLS handshakes, storage, logging, HSMs, firmware, and network performance. Existing PKI systems, protocols, and applications were optimized for RSA and ECC and often assume small key sizes and fast operations. Migrating to PQC therefore requires architectural changes, crypto-agile designs, and extensive testing across infrastructure, applications, and third-party dependencies.

What are the biggest technical challenges with PQC algorithms today?

The main technical challenges include larger key and signature sizes, increased computational overhead, and ecosystem immaturity. PQC algorithms such as ML-KEM and ML-DSA increase bandwidth usage and memory requirements, which can strain constrained environments like IoT, smart cards, and embedded systems. In addition, many protocols and hardware platforms are still adapting to support PQC efficiently, and some cryptographic libraries and devices are not yet fully optimized or certified.

Why is hybrid cryptography considered necessary during the PQC transition?

Hybrid cryptography is necessary because PQC algorithms are still new and classical algorithms remain trusted today. A hybrid approach combines classical and post-quantum algorithms so that security holds even if one algorithm is later weakened. This approach ensures backward compatibility, reduces migration risk, and aligns with guidance from NIST, NSA, and ENISA. Hybrid deployments allow organizations to transition gradually while maintaining interoperability and compliance during the multi-year migration period.

How do legacy systems and vendors slow down PQC adoption?

Many legacy systems have cryptography hard-coded into firmware, protocols, or application logic, making algorithm replacement difficult or impossible without major upgrades. Additionally, organizations depend on vendors, cloud providers, and hardware manufacturers for PQC support. If vendors are not PQC-ready, enterprises cannot migrate critical systems independently. This creates a dependency-driven timeline, where PQC adoption must align with vendor roadmaps, software updates, and hardware refresh cycles.