SSH vs. SSL: Know the Key Differences

Encryption is a no-brainer when managing a WordPress site. But when it comes to the terminologies associated with it, like SSH and SSL, things often get mixed up.

SSH vs. SSL is a confusion that stems from the fact that both these protocols share similar goals—to help encrypt and authenticate the data between two systems, like your laptop and your website’s server.

However, they serve distinct purposes, and in this blog, we’ll try to break it down for you.

What Is SSL?

SSL (Secure Sockets Layer) is a protocol that keeps the data between your browser and a website safe. You’ve probably seen a small padlock icon in your browser’s address bar when visiting a secure site. That’s SSL. It lets you know the site is using encryption to protect your data.

SSL has two main purposes: data encryption and authentication.

• Data Encryption: SSL creates an encrypted “tunnel” between your browser and an online server. When you enter sensitive info like your credit card number or password, SSL scrambles the data, so even if someone intercepts it, they’ll only see gibberish.

• Authentication: Before the transaction starts, your browser checks the website’s SSL certificate to make sure it’s legit. This prevents your data from being sent to a fake or malicious server.

Suppose you have an online store on WordPress. When visitors check out, they need to trust that their payment details are safe. By installing an SSL certificate, you’re encrypting their data during the transaction. It builds trust and prevents Man-in-the-Middle attacks. Without SSL, your visitors will see a “Not Secure” warning, which is a surefire way to scare them off.

How Does SSL Work?

SSL/TLS is a client-server model. For a client to connect to a server securely, both parties go through what is called the “SSL handshake”. Let’s take a browser-server connection as an example to see how the handshake using the RSA algorithm works.

Client Hello: The browser connects to port 443 and initiates an SSL handshake with the server. It sends a “Client Hello” message that contains information like the SSL versions and cipher suites supported by the client and a randomly generated 32-byte number called the Client Random.

Server Hello: The server replies with a “Server Hello” message. It selects a compatible SSL version and cipher suite. It generates its 32-byte random number, or the Server Random, and sends it back with its SSL certificate, which contains its public key.

Server Authentication: The browser then verifies the server’s SSL certificate to ensure authenticity. It checks if the certificate is issued by a trusted certificate authority (CA), its expiration date, and its status. The browser confirms the server’s legitimacy if the certificate passes these checks. If not, the user is warned, and the connection is typically terminated.

Client Key Exchange: The browser then creates a pre-master secret, a 48-byte random number, encrypts it using the server’s public key, and sends it back. Since only the server possesses the private key corresponding to its public key, it can decrypt the pre-master secret.

Session Key Generation: At this stage, the browser and the server use the pre-master secret and the Client Random and Server Random to compute a shared session key. This symmetric key will encrypt and decrypt all data exchanged during the session and will be discarded once the session ends.

Session Key Verification: The browser sends a “Finished” message encrypted with the session key to verify that the session key is correctly shared. If the server successfully decrypts this message, it returns its encrypted “Finished” message to the browser. Once both messages are exchanged and verified, the handshake is complete, and the connection is established.

Advantages and Disadvantages of SSL

What is SSH?

SSH, or Secure Shell, lets you log into a remote computer and execute commands like managing your website’s server. It creates an encrypted channel between your system (the client) and the server for secure communication.

Let’s say you want to install a new WordPress plugin like WP Umbrella on your laptop. Instead of navigating through your website’s dashboard, you open a terminal and use SSH to log in.

Here’s what happens:

Establishing the Connection: You type a command: ssh username@yourserver.com. It tells your computer to initiate a connection. The system prompts for authentication via password or SSH key (your stored digital credential).

Access Granted: Once authenticated, you’re securely inside the remote server. Everything you type now interacts directly with it.

WordPress developers often leverage SSH to run WP-CLI (WordPress Command Line Interface) to manage WordPress installations directly from the terminal. In addition to server management, SSH is the backbone of other tools like SFTP (SSH File Transfer Protocol). Unlike traditional FTP, SFTP uses SSH tunneling to transfer files and mitigates the risk of data interception.

How Does SSH Work?

The Client-Server Foundation: SSH operates on a client-server system. The SSH client is software on your computer that talks to remote hosts, while the SSH server runs on the remote system, listening for connections through port 22.

Server Verification Process: The first connection triggers a verification sequence. Your client and the server negotiate encryption methods, and you’ll verify the server’s public key. This key is saved in your “known_hosts” file for future reference, automating subsequent verifications and ensuring you’re always connecting to the legitimate server.

Creating A Secure Channel: Following verification, both parties use the Diffie-Hellman algorithm to generate a session key. This creates a secure, encrypted tunnel for all communications without ever transmitting the actual key across the network.

Proving Your Identity: Authentication happens through either passwords or SSH keys. While passwords work, SSH keys provide superior security. With key-based authentication, your client proves its identity by responding to an encrypted challenge from the server. Only a client with the correct private key can decrypt and respond properly.

Advantages and Disadvantages of SSH

SSH Versus SSL: When to Use What

SSH and SSL are two different but critical protocols for WordPress developers. Use SSH to manage remote servers and run commands and SSL to encrypt sensitive data of your website visitors.

To maintain this security across multiple WordPress sites, WP Umbrella can be your go-to plugin. It provides real-time alerts on Slack or email if your SSL certificate becomes inactive, scans for vulnerabilities every six hours, and monitors uptime and PHP errors.

Try the 14-day free trial (no credit card required) to see how WP Umbrella helps you stay ahead of the issues before they affect your clients and focus on delivering results, not solving problems.