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Uploading an SSH Key

Last edited by Julia Roigk

You can log onto the CLAIX systems using your login name and password (unix password), or the Secure Shell Protocol (SSH) by authenticating yourself via a private key file on your local machine. In the latter case, the corresponding public key file which the server uses to validate your identity has been saved on the HPC file system in the folder .ssh in your user directory up until now. This public key file is now moving to RegApp.

In order to use it for your HPC Account, you need to first upload the file to RegApp. Note that the SSH Key is set to automatically expire after a certain amount of time. Once it is expired, you cannot add the same key again but need to generate a new key pair.

To learn more about SSH, you can check out wikipedia or look up how-tos for other services, such as github.

Generating your SSH Key

Use your SSH key generation tool of choice, such as ssh-keygen manual or puttyGen. Make sure to generate a key of sufficient length to make it secure. To ensure your key cannot be abused, set an appropriately strong password for the private key file. Without such a password, your credentials are very vulnerable.

Strong passwords may be cumbersome to use in everyday cluster access. Help comes in the form of an ssh-agent (manual).

Once you have generated the pair of files, save the private key file in the folder .ssh on your user directory (~/.ssh on Linux, /c/users/[username]/.ssh on Windows). You can save the public key file in the same location, or move it elsewhere.

Note: Access to the login18-4.hpc.itc.rwth-aachen.de node requires password and second factor on first connection within a certain time frame. If you use an ssh config file (a file in your .ssh folder named config; for more info query your preferred search engine or start here), make sure that for this domain (e.g., *.hpc.itc.rwth-aachen.de) you are not using the public key as your preferred authentication method (i.e., do not set PreferredAuthentications publickey for this domain). Doing so will prevent the password request and thus login.

Uploading the Public Key

Screenshot of the RegApp main dashboard, showing the main navigation ribbon after expanding it from the 'Index' menu point. The new ribbon has three links: Personal Data, My SSH Pubkeys, and My Tokens.

To upload your public key, hover your mouse over the menu point Index in the navigation ribbon on top. This will expand the menu. Click on My SSH Pubkeys. This will take you to the SSH key overview.

Screenshot of the overview over the SSH keys. It displays the already added keys along with their name, expiration date, key type, SHA256 Fingerprint, and associated services. The option to revoke each key and add new ones is also given.

In the overview, your added keys are listed with their relevant information and the option to revoke each key. Note that you can only ever add a certain key once, even after revoking the key or letting it expire. You cannot reuse your keys and will need to generate a new key in these situation.

To add a new public key, use the button Add SSH Key. This brings up the dialogue to upload your public key.

Dialogue pop-up to add a new SSH public key.

Open your saved public key (the file ending in .pub) and copy the key sequence, or copy it directly from the application used to generate it. Paste it into the text box SSH Key. Do NOT upload your private key! Give your public key a name, e.g. to differentiate keys associated with different machines.

You can now register this public key with the services available in RegApp.

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