Now it is possible to create the signature files easily using the
command generate-signature-key with the correct arguments.

The command generate-signature-key works without any argument as well.

To check the arguments you must run with the parameter --help/-h.

It'll generate two file, one is a private key and the other is a
X509 certificate file.

Those files must be used by networkcache to play with signature.

The private key is required to sign the message before uploading it to
shadir. And the certification file is required to verify the signature.