How to sign a package of documents with an EDS on a client (in a browser)?

Question

Electronic digital signature

How to sign on the client / in the browser documents uploaded through the form, and then send to the server for "validation". ?
In which direction to "dig"?

Answer 1

To have legal force - dig in the direction of licensed solutions, crypto about for example, like someone else was.
If it's just for yourself, then dig in the direction of documentation-articles about how the digital signature works, certificates, rsa, and so on.
On Windows, you can use system certificates and keys, on other systems I'm not sure. it is highly likely that keychain can be used on OSX.