Mastering Linux Security and Hardening

Signing a file without encryption

If a file isn't secret, but you still need to ensure authenticity and integrity, you can just sign it without encrypting it:

donnie@ubuntu:~$ gpg -s not_secret_for_frank.txtYou need a passphrase to unlock the secret key foruser: "Donald A. Tevault <[e-mail]>"2048-bit RSA key, ID 9FD7014B, created 2017-10-27gpg: gpg-agent is not available in this sessiondonnie@ubuntu:~$ ls -l. . .-rw-rw-r-- 1 donnie donnie  40 Oct 27 19:30 not_secret_for_frank.txt-rw-rw-r-- 1 donnie donnie 381 Oct 27 19:31 not_secret_for_frank.txt.gpg

Just as before, I create a .gpg version of the file. When Frank receives the file, he may try to open it with less:

frank@ubuntu:~$ less not_secret_for_frank.txt.gpg"not_secret_for_frank.txt.gpg" ...