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Security Fundamentals & Crypto · Intermediate

M of N Control

Requiring any M of N designated custodians to cooperate to perform a sensitive operation.

Definition

M of N control provides both security (no single person can act alone) and resilience (not every custodian is needed). It is used to activate HSMs, unseal secrets managers, and recover keys. It is commonly implemented with Shamir's Secret Sharing.

Example

A 3-of-5 quorum of administrators must present their key shares to unseal HashiCorp Vault.

Exam tip

M of N combines split knowledge with availability; losing a few custodians does not lose the key.

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