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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def cmd_signing_setup(self, args):
        '''setup signing key on board'''
        if len(args) == 0:
            print("usage: signing setup passphrase")
            return
        if not self.master.mavlink20():
            print("You must be using MAVLink2 for signing")
            return
        passphrase = args[0]
        key = self.passphrase_to_key(passphrase)
        secret_key = []
        for b in key:
            secret_key.append(ord(b))

        epoch_offset = 1420070400
        now = max(time.time(), epoch_offset)
        initial_timestamp = int((now - epoch_offset)*1e5)
        self.master.mav.setup_signing_send(self.target_system, self.target_component,
                                           secret_key, initial_timestamp)
        print("Sent secret_key")
        self.cmd_signing_key([passphrase])