Skip to main content
RelixQBEYOND QUANTUM
Menu
Request demo

HNDL

Harvest Now, Decrypt Later Fundamentals

Harvest-now-decrypt-later (HNDL) risk can begin with a capture today, before a cryptographically relevant quantum computer exists. This course builds a repeatable way to reason about that conditional exposure — remaining secrecy, realistic capture paths, the mechanism protecting the data, and evidence confidence. Every lesson opens with a narrated film that works the same reasoning on screen. Prior completion of [PQC Foundations](/academy/pqc-foundations) is recommended but not required.

Beginner to intermediateLevel
75-100 minutesEst. workload
7Lessons
43 min 47 secLesson films (7)

Who this course is for: Security engineers, architects, developers, security leaders, and risk professionals who need to decide what to migrate first, not just that migration is coming.

Estimated breakdown: 44 min reading, 30 min optional written practice, and 15 min for the final assessment. These are author estimates, not timed requirements.

Your progress

Checking your progress in this browser…

The core question

"What data may already be at risk before cryptographically relevant quantum computers arrive?"

Outcomes

What you can do when you finish.

  • Explain what harvest-now-decrypt-later means and why it creates risk today even though no cryptographically relevant quantum computer exists yet.
  • Distinguish HNDL confidentiality exposure from future forgery and long-term signature-verification concerns.
  • Evaluate a specific data flow against four variables — confidentiality lifetime, harvestability, protection path, and evidence confidence — to judge its exposure.
  • Apply Mosca's inequality (X + Y > Z) to hypothetical scenarios and explain what it cannot prove about any record or quantum-computer date.
  • Compare concrete data flows using evidence, uncertainty, impacts, and migration constraints; justify a conditional first work tranche.

Topics

What the course covers.

What harvest-now-decrypt-later (store-now-decrypt-later) meansWhy HNDL creates risk before any quantum computer existsConfidentiality risk vs. signature forgery and archival verificationData confidentiality lifetimeHarvestable surfaces: transit, backups, third parties, logs, and replicasThe protection path from data to the cryptography actually guarding itShor's algorithm vs. Grover's algorithm and why the difference mattersWhy forward secrecy does not stop HNDLHybrid key exchange and X25519MLKEM768Evidence confidence and what "unknown" meansMosca's inequality (X + Y > Z) and the exposure windowPrioritizing migration candidates across real data classes

Recommended first

Consider these before starting.

Post-Quantum Cryptography Foundations

Quantum computing does not threaten all cryptography equally. This course distinguishes vulnerable classical public-key mechanisms from symmetric and hash operations, explains the NIST replacement standards, and traces a synthetic protection path from key exchange to certificates and backups. Written practice and a full architecture case show how to inventory, test, and sequence a bounded migration.

Course outline

Modules and lessons.

Module 1

The exposure

What harvest-now-decrypt-later actually means, why it creates risk before any quantum computer exists, and why it is a confidentiality problem rather than a forgery problem.

  1. What HNDL means7 min read7 min 10 sec

    Define HNDL, its adversary model, and why it is a confidentiality problem, not a forgery problem.

Module 2

The four variables

Four variables turn a vague sense of exposure into a defensible judgment: how long the data must stay confidential, where it can actually be captured, what cryptography actually protects it, and how confident the evidence behind all three is.

  1. Confidentiality lifetime6 min read5 min 56 sec

    The first variable: how many years a specific piece of data must remain secret, and why that number, not the algorithm, drives urgency.

  2. Harvestability6 min read5 min 43 sec

    The second variable: harvestability — the concrete surfaces where an adversary could plausibly capture protected data today.

  3. Protection path7 min read6 min 34 sec

    The third variable: tracing a data flow to the specific cryptographic mechanism that actually protects it, and whether that mechanism is quantum-vulnerable.

  4. Evidence & confidence5 min read4 min 50 sec

    The fourth variable: how confident the evidence is behind the other three answers, and how to treat what is genuinely unknown.

Module 3

Deciding

Turning the four variables into a decision: the exposure window and Mosca's inequality, then a worked example that ranks real data classes in priority order.

  1. Mosca's inequality6 min read6 min 21 sec

    How to combine confidentiality lifetime and migration time into an exposure window, using Mosca's inequality as a planning heuristic, not a measurement.

  2. Worked example7 min read7 min 14 sec

    Compare health records, signed firmware, and session analytics; distinguish exposure rank from a conditional program order.

Credential

HNDL Fundamentals — Certificate of Completion

Awarded after the final assessment, which is graded server-side so the score cannot be a number the browser chose.

Explaining HNDL exposure without invented timelinesDistinguishing confidentiality risk from signature and integrity riskAssessing data confidentiality lifetimeMapping realistic data-capture surfacesApplying Mosca's inequality as a planning heuristicPrioritizing migration candidates with defensible reasoning

Every issued credential can be checked at RelixQ Academy credential verification.

Final assessment

14 questions · 80% to pass

Scenario-based, timed only by your own pace. Retake it as many times as you need.

Go to the final assessment