Generating SSH Keys

SSH (Secure Shell) keys provide a secure way to authenticate with remote systems without using a password. This guide will walk you through generating a new SSH key pair on your local machine.

What are SSH Keys?

SSH keys are a pair of cryptographic keys used to authenticate a user with a remote server. The key pair consists of:

  • Private key: Kept secret and stored on your local machine.

  • Public key: Shared with the server you want to access.

Once the server has your public key, it can verify your identity using your private key.

Generate a Key Pair

To generate a new SSH key pair:

  1. Open your terminal

  2. Run the following command:

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

NOTE: ssh-keygen defaults to using ed25519, but some older versions may default to RSA. Use the -t flag to specifcy the key type.

  • -t ed25519 specifies the key type.

  • -C adds a label to your key, typically your email address.

  1. You’ll be prompted to choose where to save the key. The default location is generally /home/user/.ssh/id_ed25519

  2. You’ll then be asked to enter a passphrase. This step is optional, but reccommended. Adding a passphrase provides extra security if your private key is ever stolen.

View Your Public Key

After generation, your keys will be stored in:

  • Private key: ~/.ssh/id_ed25519

  • Public key: ~/.ssh/id_ed25519.pub

To view and copy your public key, use:

cat ~/.ssh/id_ed25519.pub

You can now add this public key to your GitHub, GitLab, or any remote server’s ~/.ssh/authorized_keys file.

Add SSH Key to Agent

To use your SSH key without entering the passphrase every time:

  1. Start the SSH agent in the background:

eval "$(ssh-agent -s)"

  1. Add your key to the agent:

ssh-add ~/.ssh/id_ed25519

Ed25519 vs RSA

  • RSA stands for Rivest-Shamir-Adleman and is a type of public-key cryptography algorithm that is used with legacy system compatibility. RSA uses an asymmetric algorithm that’s based on integer factorization. It is generally slower and requires longer keys to meet modern standards. The key file format is similar to Ed25519 and reads like id_rsa/id_rsa.pub.

  • Ed255519 is a high-security, high-performance digital signature scheme. It is asymmetric and is based on elliptic curve cryptography, specifically the Edwards-curve Digital Signature Algorithm (EdDSA) and utilizes the Curve25519 elliptic curve. It is generally faster, is fixed at a size of 256 bits, and is designed for modern cryptographic needs. The key file format reads like id_ed25519/id_ed25519.pub.

Resources