PKI

The fleet sets the answer: the root key and its certificate's validity window must both outlast the last box in service, typically two decades for consumer hardware. Succession is decided at manufacture, because afterwards nothing about the anchor can be changed.

Decide by reachability, not preference. Anchor lifetimes must exceed the interval at which you can actually change a host's lists; adding an anchor is a campaign and removing one is harder, so plan succession and inventory before the first install.

A password, and nothing else. The key travels as a pkcs8ShroudedKeyBag encrypted under a password-derived key, with MacData providing password-based integrity, so the file's security is the strength of that password against unlimited offline guessing.

A file holds a certificate; a trust anchor is an input a validator is given. Per RFC 5280 that input is a trusted issuer name, a public key algorithm, the public key and optional parameters - a self-signed certificate merely carries them.

DER is the single canonical byte encoding of the certificate's ASN.1, and the issuer signs the DER encoding of the TBSCertificate. PEM is base64 armour around those same bytes — a transport wrapper, not a different certificate.

Each signed ACME request consumes a one-time nonce, so parallel workers drawing from one pool race and lose. The badNonce error response carries a fresh Replay-Nonce, and the client should retry the same request with it rather than failing the run.

An inclusion proof shows one entry is in the tree a given signed tree head commits to. A consistency proof shows an earlier tree head's tree is a prefix of a later one, so the log appended and rewrote nothing.

A CAA record lets the domain holder publish which certificate authorities may issue for a name. The issuing authority looks it up before signing, climbing to parent domains if the exact name has none; relying parties never check it.

A full list carries every unexpired withdrawal and only grows, which is expensive to re-fetch. A delta carries just the changes since a base list, and its critical deltaCRLIndicator extension names that base list's cRLNumber, so a validator can tell whether its cached base matches.

Cross-certification. The same CA name and public key can be certified by more than one issuer, so a verifier reaches whichever anchor its own certificates and anchor list allow - and both paths verify at once.