First of all you should never need a canonical representation. If you think you do, you're almost certainly wrong. In particular you should not design protoco

First of all you should never need a canonical representation. If you think you do, you're almost certainly wrong. In particular you should not design protocols so that you have to re-encode things in order to validate signatures. So then you don't need DER or anything like it. Second, ASN.1 is fantastic. You should at least study it a bit before you pick something else. Third, pick something you have good tooling for. I don't care if it's ASN.1, XDR, DCE RPC / MSRPC, JSON, CBOR, etc. Just make sure you have good tooling. And don't pick XML unless you really need it to interop with things that are already using XML. EDIT: I generally don't care about downvotes, but in this case I do. Which part of the above was objectionable? Point 1, 2, or 3? My negativity as to XML for protocols? XML for docs is alright.