PQC Engineering Guide

Quantum computers will break the cryptography protecting your applications. This guide helps you understand what’s changing, choose the right replacement algorithms, and plan your migration — all without a PhD in mathematics.

Who This Guide Is For

You’re a backend or infrastructure engineer who understands TLS, SSH, and key management. You don’t need to know lattice theory or formal security proofs. You need to know:

• What’s breaking and when
• What to replace it with
• How to do it in your stack

Guide Contents

#	Section	What You’ll Learn
1	Why PQC Matters	The quantum threat, what breaks, and the 2035 deadline
2	PQC Algorithms	The 5 NIST-standardized algorithms and when to use each
3	Algorithm Comparison	Key sizes, speeds, and memory — engineering data tables
4	Integration Patterns	How PQC fits into TLS, SSH, and VPN protocols
5	Libraries & Tools	PQC libraries for Rust, Go, Python, Java, C/C++, and JS
6	Migration Guide	Four-phase roadmap from classical crypto to PQC
7	Glossary	PQC terms explained in plain engineering language

Quick Decision Tree

flowchart TD
    A[What do you need?] --> B{Key exchange<br/>or signing?}
    B -->|Key Exchange| C[ML-KEM<br/>FIPS 203]
    B -->|Digital Signatures| D{Signature size<br/>priority?}
    D -->|Smallest signatures| E[ML-DSA<br/>FIPS 204]
    D -->|Smallest keys| F[SLH-DSA<br/>FIPS 205]
    D -->|Balanced| G[FN-DSA<br/>FIPS 206]
    A --> H{Backup KEM<br/>different family?}
    H -->|Yes| I[HQC<br/>FIPS 207]

    classDef dark fill:#6b8e6b,stroke:#4a6a4a,color:#2c3e50
    classDef accent fill:#5a8eaa,stroke:#3a6e8a,color:#2c3e50
    classDef highlight fill:#8e6b8e,stroke:#6e4a6e,color:#2c3e50
    classDef warm fill:#8e7060,stroke:#6e5040,color:#2c3e50

    class A dark
    class B accent
    class C,I highlight
    class D accent
    class E,F,G warm
    class H accent

How to Read This Guide

• In a hurry? Read Why PQC Matters (10 min) and the Algorithm Comparison tables.
• Choosing a library? Jump to Libraries & Tools.
• Planning a migration? Start with the Migration Guide.
• Reading end-to-end? Follow sections 1 through 7 in order.

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Last updated: 2026-02-13