Install a public Key for a SSH connection
Public Keys are a form of asymetrical encryption that is basically the industry for non-password-authentification.
I’m assuming you have already set up a SSH-Server, if you haven’t you can take a look here. Make sure this line is set:
PubkeyAuthentication yes
Generating a key
Execute ssh-keygen and follow the wizard. This will generate a rsa-key by default, here is a small comparison if you want to select another one and why you may want so (execute ssh-keygen -t <nameOfAlgorythm> in order to select anything else than RSA). You want to use the default path in most cases, although if you really want to, you can change it.
| Algorythm | Description |
|---|---|
| rsa | A very old alrgorythm, has a keysize between 2048 bits and 4096 bits. It is save to use for now but it is expected to be breached in the near future. |
| dsa | An old US based algorythm that uses a keysize of 1024 bits, not recommended for use anymore |
| ecdsa | Standardised by the US government, uses keysizes of 256, 384 or 521 bits. It is a lot more efficient thatn rsa but not supported by every device yet (old devices might get some issues) |
| ed25519 | Very new algorythm introduced by OpenSSH, not suported by everything. |
Copying the public Key to the server
After creating the keypair which will be located under ~/.ssh and most likely be called id_rsa for the private key, and id_rsa.pub for the public key. You should pay attention that you’re never giving away the private key (id_rsa) to anyone, it is used to identify whoever owns it as you and can be very easily used to get access to sensitive information and your server.
There are multiple ways of getting the Public Key to the server. In the end you just have to add a file to the servers ~/.ssh/authorized_keys file. That file looks something like this:
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABgQDN9xGcvqmkT4gHFBIVHOR7Vjafu0IrRigFEOTyAj....... host13@Workstation
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABgQC6pBKCVNyY3ZLWoQ3rdT7HdMMAlnQ5bAs7AE71PH....... host13@SchoolLaptop
Every line represents a seperate clients Public Key, so just copy the contents of your Public Key to your servers authorized_keys-file.
Alternatively you can use ssh-dopy-id -i <pathToYourPublicKey> <serverUsername>@<serverHostname> to copy it to the server by command line (requires the ability to connect to that server though).