HTTP Signatures security boundaries

• Signing a Content-Digest field protects that field's value; it does not compare the digest to the message body. Applications must perform body-digest verification separately.
• Signature verification and policy acceptance do not replace authorization.
• HTTP framework adapters must provide complete request/response context, including trailers, before signing or verification.
• This package defines the atomic nonce-store contract but does not provide a production distributed implementation.

Use verification policy to enforce application acceptance requirements, including an explicit finite window for opt-in replay protection. Bind keys to trusted credentials rather than letting an incoming alg select the algorithm. Follow the message-context contract to keep headers and trailers separate.