Support JSON Canonical Scheme (JCS) - RFC 8785

[pzingg]

In order to implement Data Integrity Proofs for linked data, Elixir should have a fast JSON encoder that compiles with RFC 8785.

I think there are only few tricky points:

1 [ ]. Encoded string keys and values must be escaped by the RFC's section 3.2.2.2.. This may already be happening in Jason. 2 [x]. Floats must be encoded per the Ryu algorithm according to the RFC's section 3.2.2.3.. I think Jason now handles this for OTP > 25 with the [:short] option for in :erlang.float_to_binary/2. 3 [ ]. Encoded objects (recursively and when found in arrays) must have their properties sorted in UTF-16 integer order per the RFC's section 3.2.3

[michalmuskala]

The string encoding should be as defined in the RFC if you use the escape: :unicode_safe option.

The 3rd point would likely be best handled by a pre-pass that encodes map into a Jason.OrderedObject value - this will guarantee correct ordering of keys.

There's some complexity, though, with custom protocol implementations and @derive-based values that can generally output arbitrary bytes (they shouldn't, but could in theory). For pretty-printing we handle this by having pretty-printing as a completely separate pass - after encoding.

Either way, I'm not sure it would be possible to support this in a robust way given the way the encoding protocol works.

[darwin67]

@pzingg Looks like you already did a PoC. https://github.com/pzingg/jcs

Why not try getting this in? It's quite a hurdle without JCS to do signature verification.