gpg --sign input.file
oppure per lasciare il formato in chiaro
gpg --armor --sign input.file
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Questo e` un documento in chiaro
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.3 (GNU/Linux)
iQCVAwUBP8dXH6rZ3uo/rnZpAQJVcwP/Yr1bt/729wQU53mhvELQQPv4g9PYMCNI
KY527SiL6NphLgv6C6sZ70Sv4+mF29MSZqOlPwJFbd6R5Nf5R0Qv4/6NJVPVa780
j18uwLssotlZF3bY+vm4GxdOLc9z9Jc+zdCCEH/TlSdymDKWFfLQVuNm21X6My6r
FaOix9Kn0hI=
=SEJY
-----END PGP SIGNATURE-----