Multiple signatures on a single file

[Alphax]

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Berend Tober wrote:
> Is it possible to have multiple persons sign a single file? If so, how
> is this done?
> 
> The particular scenario is currently this: Employees submit expense
> reports for business travel using a spread sheet. Current practise is
> the the employee fills out spread sheet via computer (or optionally
> prints blank spread sheet template and writes by hand with a pen),
> physically signs using pen and ink, physically delivers signed hardcopy
> to supervisor for supervisor pen-and-ink signature prior to payment
> processing.
> 
> Desired practise is to eliminate both producing hard copy and
> pen-and-ink signatures, and then re-work the process using gpg
> electronic signatures. Thus, employee would enter data into expense
> report spread sheet, save, gpg sign, mail to supervisor, supervisor
> would (presumably) open and review spread sheet, close without changing,
> gpg sign, and then return to employee or forward to accounting dept.
> 
> Sounds straightforward, but I didn't spot in the various
> manuals/guides/how-to's for gnupg how a second individual could add
> their signature after me.
> 

Use detached signatures? Generate a key to sign the document with, and
have that key signed by the supervisor?

Just my 2c...

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