Payload Mismatch when payload includes a datetime

[sramsden]

Multi Sig payload is generated via payload.to_json in JWT::Multisig#generate_jwt however the JWT gem has JWT::Encode#encoded_payload which uses JSON.generate(@payload)

The result is a slightly different datetime string but therefore a different payload and therefore an error when attempting to verify the signature from the multisig jwt.

This can be illustrated in a rails console via ..

>> now = Time.now.utc
2018-09-04 06:42:42 UTC
>> {time: now}.to_json
"{\"time\":\"2018-09-04T06:42:42.337Z\"}"
>> JSON.generate({time: now})
"{\"time\":\"2018-09-04 06:42:42 UTC\"}"

.. noting the difference in the timestamps.

What is the solution?
Either change jwt-multisig gem to use JSON.generate or have the author of the https://github.com/jwt/ruby-jwt/blob/master/lib/jwt/encode.rb change code to use .to_json

[webdev778]

very similar issue, I'm facing, it get failed when including special character '&' in payload.

ManagementAPI check_jwt error: #<JWT::VerificationError: Signature verification raised>"