How to Manage Multiple SSH Keys
with Separate GitHub Accounts.

In order to securely manage multiple SSH keys and authenticate them with GitHub, it's important to follow the correct steps.
Having multiple SSH keys is useful when you're using different machines or need to access different GitHub accounts.
Here's a step-by-step guide on managing multiple SSH keys and authenticating them with GitHub:

Step 1- Check for existing SSH Keys

• Before you generate a new SSH key, you should check your local machine for existing keys
• to list existing keys open Git Bash and run the following command line:

$ ls -al ~/.ssh

If keys exist, it will be listed in the .ssh directory. Most of the time, the directory path will be (C:/Users/YOU)

-rw-r--r-- 1 user 197121 419 Nov 29 2022 id_ed25519 // private key

-rw-r--r-- 1 user 197121 106 Nov 29 2022 id_ed25519.pub // public key

If your machine doesn't support Ed25519 algorithm, your keys might have been generated with RSA or ECDSA algorithm:

• id_rsa.pub
• id_ecdsa.pub

Step 2- Generate a new SSH Key

Depending on which algorithm is supported by your local machine, you should generate a new key with your desired email, which can be different from the initial email used with the existing key.

• In git bash, you need to navigate to where your .ssh directory is located.

$ cd ~/.ssh

• If Ed25519 is supported, run the command line below:

$ ssh-keygen -t ed25519 -C "your_email@example.com"

• If you are using a legacy system that doesn't support Ed25519 algorithm:

$ ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

• You will be asked to save the key in a specific file; usually will be the same .ssh directory, think about giving the key a unique name to differentiate between various keys, workspaces, or GitHub accounts:

$ Enter file in which to save the key(c/users/you/.ssh/id_ed25519: "unique-key-name")

The last step is to enter a passphrase of your choice, or press enter to leave it blank.

• To ensure that the new key pair are generated successfully, run:

$ ls -al ~/.ssh

You should be able to see the old & new keys as follows:

-rw-r--r-- 1 user 197121 419 Nov 29 2022 id_ed25519 // OLD private key

-rw-r--r-- 1 user 197121 106 Nov 29 2022 id_ed25519.pub // OLD public key

-rw-r--r-- 1 user 197121 419 Jul 23 2023 unique-key-name // NEW private key

-rw-r--r-- 1 user 197121 106 Jul 23 2023 unique-key-name.pub // NEW public key

Step 3- Create a Config file

If you have more than one pair of keys, you will have to create a config file in your .ssh directory to specify which key to use for each account, as the ssh-agent can't handle multiple keys:

• Create a config file at .ssh directory path by running:

$ notepad config

• Copy, paste, customize, and save the file below in your config file.

• Please note that the personal accountis the previously existed account with id_ed25519

• While the work account is the second account with newly generated key, you will need to distinguish Host by adding any word that stands out for you; I added work.

#personal account

Host github.com

HostName github.com

User git

IdentityFile ~/.ssh/id_ed25519

IdentitiesOnly yes

#work account

Host github.com-work

User git

IdentityFile ~/.ssh/unique-key-name

IdentitiesOnly yes

Double-check the config is created properly by running:

$ ls -al ~/.ssh

In case you find the config file saved as text file, run:

$ mv config.txt config

Step 4- Add SSH keys to your GitHub account

To authenticate your SSH keys, you need to add them to your GitHub account. Follow these steps:

• Run this command cat .pub in git bash to display the public key, which you will then copy.
• Go to GitHub and log in to the account associated with the SSH key you want to add.
• Go to Settings > SSH and GPG keys.
• Click on New SSH key.
• Give your key a meaningful name.
• Paste the contents into the key field on GitHub and click on Add SSH key to save.

Step 5- Time to test SSH keys

Now that your SSH keys are set up and connected to your GitHub account, you can clone or update repositories without having to enter your credentials each time. Simply use the appropriate host alias and repository URL in your terminal. For example:

# Clone a repository using the default SSH key

$ git clone git@github.com/username/repository.git

# Clone a repository using the second SSH key

$ git clone git@github.com-work/username/repository.git

Note in the second cloned repository, we added the key word work to git@github.com-work which was customized in the config file to the Host.