Key escrow

Key escrow places copies of cryptographic keys with a trusted third party, or a designated internal escrow agent, so the keys can be produced when the original holder cannot or will not provide them. The two driving cases are recovery (an employee leaves, a key is lost, and the organisation must still decrypt its own data) and lawful access (a government or court compels disclosure). Escrow trades pure confidentiality for availability: encrypted data stops being a single point of failure hanging off one person’s key.

The distinctions matter. A key recovery agent is an internal role empowered to reconstruct or retrieve keys, while escrow proper means someone else holds a copy; the exam uses both, and the safeguard for either is dual control with split knowledge, so no single administrator can recover a key alone (M of N control). Escrow only ever applies to decryption keys: a digital signature private key must never be escrowed, because a second holder destroys nonrepudiation. Certificate lifecycles and agent roles sit inside the wider PKI.

Exam relevance: if a scenario needs an organisation to decrypt data after the key holder departs, the answer is key escrow or a recovery agent, and the accompanying safeguard is M of N or dual control. The confusable is key backup, which the key owner controls; escrow specifically means a party other than the owner holds the copy, which is why signing keys are excluded.