GPG signatures are set by the sender to prove the message is originating from the sender and is unchanged. It’s signed with the private key and verified with the public key.
A bit of a nitpick, but important to keep in mind. The GPG signatures shows that someone that has access to the private key sent that message. If I somehow gets a hold of a copy of your key, I can send messages that seems to originate from you.
To nit-pick a tad more, when they have access to my key and have my passphrase so they can sign with it…
That’s why you set the passphrase on keys, gpg, ssh,… Never use a encryption without a key. That way you need posession (key) and knowledge (passphrase) to identify yourself. When you use ssh, use the ssh agent, when you have automated login which would be better to use without keyphrase, use a different pair (specify wuth -i option) and limit access with that to a fixed ip.
And always protect your key. No cloud backup…
Edit: GPG keys also can be signed. Not by specific companies (there is probably a service for that, but it’s not by design), but by other people knowing each other. That way you have a trust based on who knows who, not who has more cash…
Same with ssh keys, you can sign those as well and set sshd to accept anybody with a certificate signed by ‘x’ to access the server on the same account name the cert was issued for.
A bit of a nitpick, but important to keep in mind. The GPG signatures shows that someone that has access to the private key sent that message. If I somehow gets a hold of a copy of your key, I can send messages that seems to originate from you.
To nit-pick a tad more, when they have access to my key and have my passphrase so they can sign with it…
That’s why you set the passphrase on keys, gpg, ssh,… Never use a encryption without a key. That way you need posession (key) and knowledge (passphrase) to identify yourself. When you use ssh, use the ssh agent, when you have automated login which would be better to use without keyphrase, use a different pair (specify wuth -i option) and limit access with that to a fixed ip.
And always protect your key. No cloud backup…
Edit: GPG keys also can be signed. Not by specific companies (there is probably a service for that, but it’s not by design), but by other people knowing each other. That way you have a trust based on who knows who, not who has more cash…
Same with ssh keys, you can sign those as well and set sshd to accept anybody with a certificate signed by ‘x’ to access the server on the same account name the cert was issued for.