[baobun]

> If one has a reproducible JSON serializer

Pretty significant catch if interoperability is a concern at all. Whitespace is easy enough to handle but how do dict keys get ordered? Are unquoted numbers with high precision output as-is or truncated to floats/JS Numbers? Is scientific notation ever used and if so when?

[butvacuum]

Just so people this far down can look it up the term is Canonicalization, and its cousin collation.

These are non-trivial issues that, thankfully, some very smart and/or experienced people have usually handled for us. However, they still frequently lead to all sorts of vulnerabilities. "Stuffing" attacks sometimes rely on these issues, as have several major crypto incidents.