Key Management, Cryptographic Hardware and Escrow

Lesson plan

Level

Beginner

Time

About 60 minutes; the steps below add up to 61

Learners list everything that could go wrong with one backup key over the years, and whether 256 bits is automatically strong, before the lifecycle is named. Predictions then precede the lifecycle stages, a time-of-day key, saving a leaver’s files, a key in a file, where a CA’s key belongs, approved-algorithm claims, a sole key holder and a sole escrow holder; checks follow revocation, the TPM, a replaced motherboard, signing keys and 3-of-5 control. The habit to build: for any key, ask how it was made, where it lives, who can use it and how it ends.

Objectives

• Describe the key lifecycle and why each stage matters
• Explain entropy, and why length is not strength unless the key is random
• Compare centralised and decentralised key management
• Distinguish TPMs, HSMs and secure enclaves, and read FIPS 140 claims
• Explain key escrow and M-of-N control

Before the lesson

• Open this page on your own screen and use “Open the lesson window” to open the lesson in a second window. Share only that second window.
• Learners need the Symmetric and Asymmetric Encryption lesson first.
• A spare house key is a useful prop for escrow, with its limits.
• The lesson takes about 61 minutes. To teach it in two parts, stop after “Hardware security modules”; the second part opens with “FIPS 140-2 and FIPS 140-3”.
• In presentation mode every step is shown in turns: Next reveals one moment, part or answer at a time, and the instructor view names what is on screen and what comes next.

Steps

1. Introduction Opening

   On screen: the lesson’s title, module and number; Next adds its objectives and key terms, as the lesson page lists them; Next again begins the first step.

   Objectives on screen

   • Describe the key lifecycle and why each stage matters
   • Explain entropy, and why length is not strength unless the key is random
   • Compare centralised and decentralised key management
   • Distinguish TPMs, HSMs and secure enclaves, and read FIPS 140 claims
   • Explain key escrow and M-of-N control

   Purpose: Learners list everything that could go wrong with one backup key over the years, and whether 256 bits is automatically strong, before the lifecycle is named. Predictions then precede the lifecycle stages, a time-of-day key, saving a leaver’s files, a key in a file, where a CA’s key belongs, approved-algorithm claims, a sole key holder and a sole escrow holder; checks follow revocation, the TPM, a replaced motherboard, signing keys and 3-of-5 control. The habit to build: for any key, ask how it was made, where it lives, who can use it and how it ends.

2. 1. One key, many years Think 5 min

   Purpose: Raise the stages of a key’s life from what could go wrong.

   Ask

   • What could go wrong?
   • Is 256 bits automatically strong?

   Responses to expect

   • Theft comes first; generation and destruction need prompts.
   • On screen in turns: the opening question, its answer; then the question on whether 256 bits is strong, and its answer.

   Discussion pause: Order learners’ answers by when in the key’s life they happen.

   In the lesson window

   • Think it through: A school keeps one key that unlocks every backup it has ever made. List everything that could go wrong with that key over the years.
   • Think it through: Is a 256-bit key automatically strong?

3. 2. The key lifecycle Explain 7 min

   Purpose: Walk through the eight stages with the school’s backup key.

   Ask

   • Which stages can you name?
   • Which stage does the lost laptop trigger?

   Responses to expect

   • Rotation and revocation are often confused.
   • Diagram: step through the eight stages, then follow the school’s backup key through them; ask what could go wrong at each.
   • On screen in turns: the opening; then the question on naming the stages, and its answer; the life of a key, one stage at a time; the diagram’s stages one at a time; one key’s life at a school, starting with generation; distribution; storage; use; rotation; backup or archival; revocation; destruction, and what one mistake costs; two stages deserve a comment; the check question on the lost laptop, and its answer; rotation limits damage; destruction as protection.

   In the lesson window

   • Think it through: Name the stages a key might pass through, from the moment it is created to the moment it is no longer needed.
   • Check your understanding: In the school example, a technician’s laptop that could reach the key is lost. Which stage does that trigger?

4. 3. Entropy and randomness Predict 5 min

   Purpose: Explain entropy and why a predictable key is weak.

   Ask

   • How many keys would the attacker try?

   Responses to expect

   • 2 to the 256 is the instinctive answer.
   • On screen in turns: the opening; then the question on a key based on the time of day, and its answer; entropy; where computers get randomness; a long key from a weak source; length is not strength unless random.

   Misconceptions to challenge

   • A learner may believe: “A long key is always a strong key.” Respond: Only if it is random.

   In the lesson window

   • Think it through: A program bases each 256-bit key on the time of day in whole seconds. How many keys would an attacker really need to try?

5. 4. Centralised and decentralised key management Predict 5 min

   Purpose: Compare centralised and decentralised management, and KMIP.

   Ask

   • Which approach saves a leaver’s files?

   Responses to expect

   • Centralised management, where the organisation holds the keys.
   • On screen in turns: the opening; then two approaches, starting with centralised; decentralised; the question on a leaver’s key, and its answer; the two compared, with decentralised held back; the decentralised column; most organisations centralise; KMIP.

   In the lesson window

   • Think it through: An employee who encrypted their own files with a key only they held leaves suddenly. Which approach to key management would have saved the files?

6. 5. Hardware that protects keys Predict 8 min

   Purpose: Explain why keys belong in hardware, the TPM and its layered keys.

   Ask

   • Who could copy a file key?
   • What does a TPM belong to?
   • How is a drive unlocked after a new motherboard?

   Responses to expect

   • “The key is in the TPM” is the common simplification.
   • On screen in turns: the opening question, its answer; then a key in a file can be copied; the Trusted Platform Module, starting with key storage; measuring start-up; resisting guessing; the TPM and BitLocker; the check question on what a TPM belongs to, and its answer; a TPM does not hold every key, with where each is kept held back; where each link is kept; the check question on a new motherboard, and its answer; why the layering is deliberate.

   Misconceptions to challenge

   • A learner may believe: “The disk encryption key is in the TPM.” Respond: The TPM protects a key that unlocks the data key; both are on the drive, encrypted.

   Discussion pause: The “where it is kept” column is held back: ask where each link of the chain should live before revealing it.

   In the lesson window

   • Think it through: A key is stored in an ordinary file on a server. Who could copy it?
   • Check your understanding: A TPM belongs to what?
   • Check your understanding: A laptop’s motherboard, and with it the TPM, is replaced. How can the encrypted drive still be unlocked?

7. 6. Hardware security modules Predict 5 min

   Purpose: Describe HSMs and secure enclaves, and compare all three.

   Ask

   • Where would a CA keep its signing key?

   Responses to expect

   • Learners often say “in the TPM”.
   • On screen in turns: the opening question, its answer; then the hardware security module, starting with keys created inside; applications send it data; tampering erases keys; volume and separation of duties; what HSMs protect; secure enclaves; TPM, HSM and secure enclave, side by side.

   In the lesson window

   • Think it through: Where would you keep a certificate authority’s signing key, which could be used to issue certificates for any website?

8. 7. FIPS 140-2 and FIPS 140-3 Predict 5 min

   Purpose: Explain FIPS 140 validation and how to read claims.

   Ask

   • Is “uses approved algorithms” validated?

   Responses to expect

   • Most say yes.
   • On screen in turns: the opening; then FIPS 140, starting with 140-2; 140-3; the question on “uses FIPS-approved algorithms”, and its answer; two cautions, starting with module and version; compliant is not validated; where FIPS 140 is required; the four security levels.

   Misconceptions to challenge

   • A learner may believe: “FIPS compliant means FIPS validated.” Respond: Validation is a tested module with a certificate number.

   In the lesson window

   • Think it through: A product says it “uses FIPS-approved algorithms such as AES”. Is it FIPS 140 validated?

9. 8. Key escrow Predict 6 min

   Purpose: Explain escrow through the administrator who left, and which keys are escrowed.

   Ask

   • What could go wrong with one key holder?
   • Which keys are not escrowed?

   Responses to expect

   • Signing keys surprise learners.
   • On screen in turns: the opening; then the question on one administrator who knows, and its answer; key escrow; the administrator who left, without escrow; with escrow; three questions about escrow, starting with who holds the copy; who may retrieve it; which keys are escrowed; the check question on which key is not escrowed, and its answer.

   If the explanation does not land: A spare key with a neighbour, and why a digital copy is riskier.

   In the lesson window

   • Think it through: One administrator set up a school’s encrypted file server and is the only person who knows the recovery key. What could go wrong, and how could it be prevented?
   • Check your understanding: Which kind of key is generally not escrowed?

10. 9. M-of-N control Predict 5 min

    Purpose: Explain M-of-N control with the school’s 3-of-5 trustees.

    Ask

    • What stops misuse by one holder?
    • How many can be absent?

    Responses to expect

    • Two.
    • On screen in turns: the opening; then the question on one holder, and its answer; M-of-N control; 3 of 5 at the school, starting with no one person alone; surviving absences; the check question on three of five, and its answer; choosing the numbers; how the most sensitive keys are handled.

    To go further

    • Why might a certificate authority require several officers to be present to activate its root key?

    In the lesson window

    • Think it through: What stops the one person who holds an escrowed key from misusing it?
    • Check your understanding: With 3-of-5 control, how many trustees can be absent while recovery is still possible?

11. 10. Security+ terminology Explain 1 min

    Purpose: Link the lesson to the Security+ wording.

    Ask

    • Which tools are listed?

    Responses to expect

    • TPM, HSM, key management system, secure enclave.
    • On screen in turns: the opening; then what the objectives do not list.

12. 11. Apply it in a new situation Apply 4 min

    Purpose: Set up independent application, ideally on a later day.

    Ask

    • Who will try these now, and who later in the week?

    Responses to expect

    • Ten years tests rotation; FIPS tests claims; 2-of-2 tests M and N.
    • On screen in turns: the opening; then the question on ten years, one key, and its answer; the question on a FIPS claim, and its answer; the question on 2-of-2 control, and its answer.

    In the lesson window

    • Apply it: One key has encrypted a company’s backups for ten years. What is the risk, and the remedy?
    • Apply it: A vendor says its device is “FIPS validated”. What should you ask for?
    • Apply it: A small charity sets 2-of-2 control on its recovery key, with two trustees. What is the weakness?

13. 12. Check your understanding Check 3 min

    Purpose: Check the lesson against the approved revision-bank questions.

    Ask

    • Answer individually, then compare before revealing.

    Responses to expect

    • The two groups of questions match the two halves of the lesson.
    • On screen in turns: the opening; then the revision questions one at a time, each followed by its answer; the next group of revision questions, starting with its first; the second revision question; the third revision question; the fourth revision question; the fifth revision question; the sixth revision question; the seventh revision question; where to practise next.

14. 13. What to remember Consolidate 2 min

    Purpose: Summarise the five points, the key terms and the misunderstandings.

    Ask

    • Without looking: the difference between a TPM and an HSM.

    Responses to expect

    • One device’s keys; an organisation’s most valuable keys.
    • On screen in turns: the opening; then the summary; the key terms; the common misunderstandings.

15. Lesson recap Closing

    On screen: the lesson’s objectives again; Next adds the closing question, which asks the class to explain each one in their own words without looking back. It says nothing about what anyone has learnt: use the answers to decide what to revisit.

    Points to listen for

    • Every stage of a key’s life can fail.
    • Random, or not strong.
    • Central control, central target.
    • TPM, HSM, enclave: three kinds of key hardware.
    • Escrow for recovery; M-of-N against misuse.

Consolidation

• Every stage of a key’s life can fail.
• Random, or not strong.
• Central control, central target.
• TPM, HSM, enclave: three kinds of key hardware.
• Escrow for recovery; M-of-N against misuse.