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Key Escrow

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Summary

PDF p.67

Key escrow involves archiving cryptographic keys with a third party to ensure they can be recovered if lost or damaged. M of N controls require a quorum of individuals to authorize key recovery operations, enhancing security. Keys can be split into parts and held by separate escrow providers to reduce the risk of compromise.

In plain words

Supplementary — not from your PDF

Key escrow means storing a copy of important keys with a trusted third party so they can be recovered if lost. M of N controls mean several people (M out of N) must approve a recovery, so no one can do it alone.

Detailed explanation

PDF p.67
  • Key Escrow
    • Definition: Archiving cryptographic keys with a third party to ensure recovery if lost or damaged.
    • Problem with Copies: Making multiple copies increases the risk of compromise and makes detection difficult.
  • M of N Controls
    • Definition: An operation requires a quorum (M) of available persons (N) to authorize it.
    • Purpose: Prevents a single individual from performing key recovery operations.
  • Key Splitting
    • Process: A key can be divided into parts, each held by different escrow providers.
    • Benefit: Reduces the risk of compromise.
  • Key Recovery Agent (KRA)
    • Definition: An account authorized to access a key held in escrow.
    • Recovery Policy: May require multiple KRAs to authorize key recovery, mitigating the risk of impersonation.

Important terms

taken from the text above
Key Escrow
Archiving cryptographic keys with a third party to ensure recovery if lost or damaged.
Problem with Copies
Making multiple copies increases the risk of compromise and makes detection difficult.
M of N Controls
An operation requires a quorum (M) of available persons (N) to authorize it.
Key Recovery Agent (KRA)
An account authorized to access a key held in escrow.
Recovery Policy
May require multiple KRAs to authorize key recovery, mitigating the risk of impersonation.
KRA Key Recovery Agent

Examples & real-world scenarios

Supplementary — not from your PDF
  • Recovery keys for company laptops held in escrow.
  • 3 of 5 administrators needed to approve a key recovery.
  • Splitting a key between separate escrow providers.

Scenario

An employee leaves and their encrypted files are needed. Two key recovery agents approve the recovery under an M of N policy, so a single rogue admin couldn't have done it alone.

Common mistakes

Supplementary — not from your PDF
  • Making lots of ad-hoc key copies 'to be safe'. More copies mean more ways to leak.
  • Thinking M of N means M keys. It means M approvers out of N.

Practical skills

Supplementary — not from your PDF
  • Design a key recovery process with separation of duties.

What I should remember

Key Points PDF p.67
  • Key Escrow
    • Third Party: Keys archived with an independent entity.
    • Risk of Copies: Increased compromise risk with multiple copies.
  • M of N Controls
    • Quorum: Requires multiple individuals to authorize operations.
    • Security: Enhances security by preventing single-person access.
  • Key Splitting
    • Parts: Key divided and held by separate providers.
    • Risk Reduction: Lowers compromise risk.
  • Key Recovery Agent (KRA)
    • Authorized Access: Accounts with permission to access escrowed keys.
    • Multiple KRAs: Required for authorization to prevent impersonation.