16^th Advanced Scientific Programming in Python

Open a terminal and start the interactive generation of a new SSH key-pair. Set your name (one single string without blanks) instead of alice in the following:

NAME=alice
ssh-keygen -f /tmp/id_$NAME

The program ssh-keygen will ask for a passphrase twice. Type a passphrase of your choice and remember it: you will have to type it quite often during the school. IMPORTANT: Do not leave the passphrase empty! If the generation is successful, you will see something like this:

ssh-keygen -f /tmp/id_alice
Generating public/private rsa key pair.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /tmp/id_alice
Your public key has been saved in /tmp/id_alice.pub
The key fingerprint is:
SHA256:RJz6ek6B7z4QbUAYT0E1lbdVftsrA1khs/KUEUGxu5A student@aspp
The key’s randomart image is:
+---[RSA 3072]----+
|    .==++ooX+. ..|
|    .o..o.. O o. |
|      .+.. * +  o|
|      ooo = =   +|
|      .+SE =   ..|
|      ..... o   .|
|       oo  . o . |
|      .oo     o  |
|       ++.       |
+----[SHA256]-----+

This will have generated two files, one for the private key /tmp/id_alice and one for the public key /tmp/id_alice.pub.

While still in the terminal, let save the public key into the system's clipboard so that we can re-use it later on GitHub. Type the following, of course using your own name and do not forget the .pub extension:

xclip -selection c /tmp/id_$NAME.pub

The contents of that file are now in the clipboard.

• Now you want to make your public key known to GitHub, so it can be used during the school for easy authentication on GitHub. Login to GitHub: https://github.com/login

• After login, click on your avatar on the top right of the page and in the resulting menu select Settings:

• This will bring you to the profile settings page on https://github.com/settings/profile . Here from the navigation sidebar on the left select SSH and GPG keys:

• This will bring you to https://github.com/settings/keys . Here press the green button on the right labeled New SSH key:

• This will bring you to https://github.com/settings/ssh/new . Here set the title to ASPP. Leave the Key type to the default Authentication key. Paste the public key you have saved in the system's clipboard into the Key field on this page by pressing Ctrl-V:

• When you are done, press the Add SSH Key green button right below.

You can now verify that your key has been added on the same page https://github.com/settings/keys :

• Insert your USB-stick
• The USB-stick will be automatically mounted in the directory /run/media/student/ASPPXX, where XX is the number of your stick
• With the following command you will move the SSH-keys to the USB-stick:

NUMBER=XX
mv /tmp/id_$NAME* /run/media/student/ASPP$NUMBER/

• Eject the USB-stick from the file manager and insert it again: a pop-up will ask you for the passphrase to unlock the private SSH key you just created
• Open a terminal and try the following:

ssh -T git@github.com

If after that you get something along these lines:

Hi Alice! You've successfully authenticated, but GitHub does not provide shell access

everything went well. If you instead get something like:

git@github.com: Permission denied (publickey)

something went wrong.