# SSH Key For Server Access

# Why you need an SSH key

When connecting to a server you need to login to the system so that the server is protected from unauthorized access. Most commonly you do this by entering a username and a password.

However, passwords have some problems:

  • If they're long and complex, they're hard to remember.
  • If they're short, they're easy for an attacker to compromise.
  • A compromised server can see your password, which most people reuse in multiple places.

A more secure way to login to a server is to use what's commonly called SSH keys. It relies on public-key cryptography to securely authenticate to the server.

To use SSH keys you create two related keys, also called a key pair:

  • A private key that only you know and you never share with anyone.
  • A public key you can freely share that you give to the server.

The server can then use the public key to issue a challenge, and only someone with the matching private key can solve the challenge. This way you prove to the server you are who you say you are.

TIP

Ethereum and Bitcoin also use public-key cryptography in a similar way, and in fact your Ethereum wallet address is just the last 20 bytes of your public key.

# How to create a key pair

First, open a Terminal on your computer, and run the following command by copy-pasting it and pressing Enter.

ssh-keygen -t rsa -b 4096 -f ~/.ssh/bwqr_rsa -C qr@bw \
    && chmod 600 ~/.ssh/bwqr_rsa \
    && ssh-add ~/.ssh/bwqr_rsa

It will then ask you for a passphrase. You can leave it empty, or type a passphrase for added security.

Now run the following command to display your SSH public key:

cat ~/.ssh/bwqr_rsa.pub

The output will look like this:

ssh-rsa AAAABreallylongtext== qr@bw

This output is what you need to provide Blockwell for server access. This is your public key.

WARNING

Never share your private key that's in the file bwqr_rsa. This file begins with something like this:

-----BEGIN RSA PRIVATE KEY-----

If someone gets hold of this private key it's as bad as someone learning your password.