kb-fediverse-http-signatures

Background knowledge about how HTTP Signatures work in ActivityPub and the Fediverse, including the signing and verification process, the public key model, authorized fetch / secure mode, key rotation, instance actors, and known interoperability quirks across implementations. Load when the user asks about implementing HTTP signatures, debugging signature verification failures, the Digest header, the (request-target) pseudo-header, keyId resolution, the publicKey property on actors, hs2019, clock skew, or federation failing between specific implementations. Also load when reviewing or writing code that signs or verifies ActivityPub requests.