Function eab_problem 

pub fn eab_problem(error: EabError) -> Problem

Maps an EabError to the Problem the caller rejects with. Structural failures – malformed base64/JSON, an unsupported alg, a url mismatch, or a payload JWK that does not match the account’s own – are malformed (400), mirroring how the outer JWS’s own SignatureError splits shape problems from signature-validity ones. A signature that simply does not verify is unauthorized (401), the same as a bad outer JWS signature.