Before we dive into this article, let's first understand what SSH keys are and why they are important.

# SSH Keys

SSH keys are a pair of cryptographic keys used to authenticate a user or device in the SSH (Secure Shell) protocol. SSH is a secure method for remotely connecting to servers and other devices, providing a secure channel over an unsecured network.

The key pair consists of a private key and a public key:

• Private Key: This key remains on your computer and should be kept secure. It is used to decrypt data that has been encrypted with the corresponding public key.

• Public Key: This key can be shared with any server or device you want to connect to. When you attempt to establish a connection, the server uses this key to encrypt a message that only your private key can decrypt, proving your identity without sending the private key over the network.

Using SSH keys for authentication offers several advantages over traditional password-based authentication:

1. Security: SSH keys are much more secure than passwords. A strong password can still be guessed or cracked, whereas SSH keys, especially those generated with a high level of complexity, are practically impossible to break.

2. Convenience: Once set up, SSH keys allow you to log in to your servers without entering a password each time, streamlining the process of remote access.

3. Automation: SSH keys enable secure automation of tasks, such as remote backups, file transfers, and deploying code, without the need to handle passwords.

Now that we have a basic understanding of SSH keys, let's proceed with the steps to set up and manage multiple SSH keys on your computer.

I’m sure if you’ve come to this article, you’re already using or have previously worked with an SSH key pair. So, let’s start by creating and using a single SSH key pair.

# Navigate to the ssh directory and create ssh keys

Enter the command ls ~/.ssh  to check the existing ssh keys, and if you dont have any exitsting ssh keys then create the ssh key pair using - 

Normally, we use this command to generate an SSH key pair.

ssh-keygen -t ed25519 -C "[email protected]"

now press Enter, You should see the prompt: Enter passphrase (empty for no passphrase):. It's entirely your choice whether to set a passphrase or not. If you prefer not to use a passphrase, just press Enter twice when prompted to Enter same passphrase again and this will generate ssh keys id_rsa and id_rsa.pub (name of default key).

However, since we are setting up multiple SSH keys, we should name the keys differently. This way, you can easily distinguish between them and manage them more effectively in the future.

ssh-keygen -t ed25519 -f ~/.ssh/github -C "[email protected]"
# OR
ssh-keygen -t ed25519 -f ~/.ssh/bitbucket -C "[email protected]"

Each command will create two files: one with the name you entered and a second with the .pub extension. For example, you'll get github and github.pub, as well as bitbucket and bitbucket.pub. In my case, I use GitHub for personal projects and Bitbucket for work-related tasks, so I created these two ssh keys.

# Set Up config file

Now, In the same .ssh folder, there should be a config file (without any extension). If the file doesn't exist, you can create it by using touch config command.

Next, we'll add entries to specify which key to use in different situations.

# personal key for my GitHub
Host github.com
    HostName github.com
    IdentityFile ~/.ssh/github
	
# work key for BitBucket
Host bitbucket.com
    HostName bitbucket.com
    IdentityFile ~/.ssh/bitbucket

# Default
Host *
  IdentityFile ~/.ssh/id_rsa

# Update keys to your accounts and use them

Next, you will need to copy the public keys and paste them into the SSH keys section of your GitHub and Bitbucket accounts and now Try pull or clone a repository from either account to ensure everything is working correctly.

And that's it! We've covered how to manage multiple SSH keys on and how to specify which one to use when cloning Git repositories.

Thanks for reading!