If your instance of MarkUs is using git repositories to store student submissions, you have the option to upload a public key to MarkUs. This public key will be used to authenticate you when you clone a git repository from MarkUs over ssh.
To upload a public key, navigate to the "Key Pair" tab. Click on the "New Key Pair" link to upload a new key pair (as a file or as text) or click on an existing Key Pair to edit it. You may upload multiple public keys in this way.
For instructions on how to generate a public/private key pair see: