When you log in to a new system for the first time with the SSH protocol, the system returns a hostkey fingerprint to you:

The authenticity of host 'submit.grid.fe.up.pt (193.136.38.202)' can't be established.
ED25519 key fingerprint is SHA256:mfh3A+ztduKGbyHeNi6KYWJoEKIZ3Sv9pN2LJopFpXM.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'submit.grid.fe.up.pt' (ED25519) to the list of known hosts.

Before you type “yes” to the question posed to you, you can verify this fingerprint against the list of correct fingerprints for Grid.UP below, to check that you are indeed logged to the correct system.

ED25519
===
SHA256:mfh3A+ztduKGbyHeNi6KYWJoEKIZ3Sv9pN2LJopFpXM
MD5:44:87:aa:71:37:63:00:0c:be:f7:62:c3:1f:8e:85:03

ECDSA
===
SHA256:L9eR6CdbURKyVkfEyfpqAvW/G77shiho4TYF+xS1b8A
MD5:a9:b2:97:88:5f:c9:f5:2f:43:85:63:4f:c7:c9:fc:a7

RSA
===
SHA256:qQ07xqB3tM2Uxu7B/q/Jt6hfeb9/vpHFgtgAAof4qt8
MD5:e5:e0:20:21:e9:bf:49:ee:ff:49:ae:af:cb:ee:c6:06