Generate a key:
gpg --full-generate-key
gpg --list-keys
Export public key:
gpg --armor --export you@example.com > pubkey.asc
Encrypt/decrypt a file:
gpg --encrypt --recipient you@example.com secrets.txt
gpg --decrypt secrets.txt.gpg
Sign/verify:
gpg --clearsign message.txt
gpg --verify message.txt.asc
Inspect certificate:
openssl x509 -in cert.pem -noout -text
Test TLS endpoint:
openssl s_client -connect example.com:443 -servername example.com
Hashing:
sha256sum file.iso
openssl dgst -sha256 file.iso