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.

Interesting. What do you make of PASETO[1] and specifically PAE[2], then?

[1]: https://github.com/paseto-standard/paseto-spec/blob/master/d... [2]: https://github.com/paseto-standard/paseto-spec/blob/master/d...