Matrix does it like this as well. Servers have to serialize an object as JSON (specified as Python code), then add the signature to the object and serialize it

Matrix does it like this as well. Servers have to serialize an object as JSON (specified as Python code), then add the signature to the object and serialize it again to send it on the network. https://spec.matrix.org/v1.1/appendices/#signing-json https://spec.matrix.org/v1.1/appendices/#signing-json