I'm writing some code to digitally sign certain files (JSON, if you must know), and I'm trying to understand the use cases, not being a crypto guy myself.
I understand there are use cases where several parties all need to sign the same content, e.g. the two parties who enter a contract sign it to indicate their approval.
But are there use cases where B signs not just the content (of the contract, or whatever), but the concatenation of content plus the previously-created signature by A of the content?
Update: given this discussion, I created a proposal that I believe covers the case in case you are interested: http://upon2020.com/blog/2014/03/digital-signatures-on-json-payloads-lets-call-it-jsonsig/