When managing separate professional and personal repositories on a single macOS instance, isolating authentication credentials prevents permission conflicts. Begin by navigating to the secure shell directory.

cd ~/.ssh

Creating a New Key Pair

Generate a new key pair using the Ed25519 algorithm for improved security. Specify a unique filename to prevent overwriting existing default keys like id_rsa.

ssh-keygen -t ed25519 -C "developer@example.org" -f id_ed25519_work

During execution, the system will prompt for a passphrase. Enter a secure string twice; this protects the private key during usage.

Registering with the SSH Agent

macOS manages SSH identities through the local agent. Register the new private key to ensure it is available for authentication requetss.

ssh-add ~/.ssh/id_ed25519_work

Verify the identity is loaded by listing curent keys.

ssh-add -l

Configuring Host Aliases

To automatically select the correct key for specific repositories, define host rules in the SSH configuration file. Create or edit ~/.ssh/config.

Host github-work
    HostName github.com
    User git
    IdentityFile ~/.ssh/id_ed25519_work
    AddKeysToAgent yes

When cloning or pushing, use the alias github-work instead of the standard github.com in the remote URL.

Deploying the Public Key

Extract the public key content and copy it directly to the clipboard for easy pasting into provider settings.

cat ~/.ssh/id_ed25519_work.pub | pbcopy

Navigate to the SSH keys section of your Git provider account and paste the contents.

Verifying Connectivity

Test the authentication handshake using the configured host alias or standard endpoint.

ssh -T git@github.com

A successful response confirms the identity is recognized without granting shell access.