Understanding SSH
Definition and Purpose
SSH stands for Secure Shell. It is a cryptographic network protocol that provides secure remote administration and command execution on servers and network devices. It was developed to replace older protocols like Telnet, which sent data without any encryption. SSH secures all traffic, including passwords, to protect privacy and data integrity during a connection. This protocol is widely used for managing servers in shared, dedicated, or cloud-hosted environments. Admins and users access systems over networks that may not be trusted, so encryption is necessary to stop others from reading or changing data as it moves across the network.
How SSH Works (Key-Based Authentication, Encryption)
SSH starts with the client checking the server’s host key. On the first connection, the client saves the host key to verify future connections. This helps protect against impersonation.
Next, the client and server use public-key methods to negotiate a session key. This session key is used to encrypt data during that session. The actual commands or file transfers travel within this secure channel.
Authentication can use passwords, but using key-based authentication is much more common and secure. Here is how it works:
- The user creates a pair of cryptographic keys: a public key and a private key.
- The public key is copied to the server. The private key stays on the user’s computer and is usually protected with a passphrase.
- During login, the server uses the public key to challenge the user. Only the matching private key can solve this challenge. If so, access is granted.
All traffic between the client and server is encrypted. This includes all commands entered, files transferred, or data tunneled through SSH.
Common Use Cases (Servers, Automated Scripts)
- Remote server management: IT staff log in to Unix or Linux servers to perform system updates, installs, log checks, and troubleshooting.
- Secure file transfer: Admins and scripts use SCP (secure copy) or SFTP (SSH File Transfer Protocol) to upload or download files in encrypted form.
- Automated scripts: Automated deployments, backups, or remote health checks run over SSH. Key-based authentication allows scripts to connect without manual password entry.
- Port forwarding or tunneling: SSH can forward network ports between computers to encrypt data streams for applications like databases, email, or even web servers.
Understanding SSL/TLS
Definition and Purpose
SSL means Secure Sockets Layer. It has been replaced by TLS, or Transport Layer Security. Both serve the same core purpose: to secure communications across the internet, especially between web browsers and servers. These protocols allow websites to protect user data from eavesdropping, tampering, and impersonation. SSL/TLS ensures that the server is authentic, secures data transfers through encryption, and prevents attackers from reading or modifying information as it travels.
How SSL/TLS Works (Certificates, Public-Key Encryption)
SSL/TLS depends on digital certificates. A Certificate Authority (CA) issues each certificate after verifying information about the site or company.
Here is how the process works:
- When you visit a website, your browser and the server exchange messages to begin an SSL/TLS handshake.
- The server presents its digital certificate to the browser.
- The browser checks the certificate’s validity, including the issuer and expiration date. It also checks that the certificate’s domain matches the website domain.
- If the certificate is valid, the browser and server negotiate which encryption technologies to use.
- They perform a public-key handshake to create a shared secret session key. This session key encrypts all further communication during that visit.
Most sites use SSL/TLS with web traffic (HTTPS), but email servers, APIs, and other services also use these protocols to secure data.
Common Use Cases (Websites, Secure Communications)
- HTTPS websites: Secures connections between browsers and web servers for logins, purchases, and private browsing.
- Email security: Protects email in transit for protocols like SMTP, IMAP, and POP3.
- APIs and web service connections: Encrypts API traffic and integrations between servers, including payment systems and software-as-a-service connectors.
SSH vs SSL – Technical Comparison
Protocol Architecture and Ports Used
| Aspect | SSH | SSL/TLS |
| Default Port | 22 | 443 (HTTPS), 465, 993 |
| Network Layer | Runs on the network layer | Runs on the transport layer |
SSH uses port 22 by default. It sets up a secure tunnel between endpoints. SSL/TLS most often runs on port 443 for HTTPS web traffic, but can use other ports for email and legacy services. SSL/TLS encrypts data at the application level.
Authentication Methods
SSH verifies the server host and the user. Host checks happen using the server’s host key. User verification can be password-based, but best practice is to use public/private key-based authentication.
SSL/TLS confirms the server’s identity using digital certificates signed by trusted CAs. The user’s browser must trust the CA for the process to succeed. Client-side certificate authentication is possible but not common for most websites.
Encryption and Handshake Processes
SSH starts with a handshake. Client and server agree on encryption algorithms and exchange keys using public-key cryptography. They switch to symmetric encryption for the rest of the session. User authentication happens after the handshake.
SSL/TLS also uses a handshake to share a session key. It uses asymmetric encryption during the handshake, then symmetric encryption for session traffic. SSL/TLS uses X.509 digital certificates. SSH uses unique host keys and optional user key pairs.
Use Case Comparison
Remote Server Access (SSH)
SSH is the standard for remote shell access and server administration. System administrators rely on SSH to maintain, update, and troubleshoot servers in data centers or cloud environments. SSH gives control over the command line and secure file transfer abilities.
Browser-to-Server Security (SSL/TLS)
SSL/TLS is fundamental for secure website access. It encrypts data sent between browsers and web servers. This protection is important for websites that require logins, handle payment data, or share any sensitive user information.
API Connections and Integrations
APIs that send private or sensitive data use SSL/TLS to secure the connection. This is common for payment processors, user authorization flows, and webhooks between cloud services. SSH is rarely used for API traffic, but is useful for managing the server hosting the API or securing Git repository access.
Performance & Overhead
Connection Latency and Handshake Speed
SSL/TLS handshakes are usually more complex and take slightly longer than SSH handshakes. This is due to certificate checking and additional steps during validation. TLS 1.3 has made progress in speeding up handshakes for HTTPS. SSH handshakes are faster since they are designed for quick, interactive command-line access.
Impact on Data Transfer Performance
Both protocols introduce encryption overhead that can slow down data transfers, especially on older or lower-powered servers. TLS allows session resumption and persistent connections, which can reduce handshake time for web browsing. SSH encrypts all data, which can slow very large file transfers in busy environments. Both SSH and TLS support data compression, but its impact depends on server configuration.
Resource Usage on the Host
SSH and SSL/TLS use system resources to perform cryptographic tasks. The load increases with more active connections and higher-strength encryption. Modern hardware usually manages these demands with ease, except in cases with very high volume or on limited-resource hosting plans.
Security and Vulnerabilities
Threat Models and Typical Attacks
With SSH, attackers focus on brute-forcing passwords or exploiting weaknesses in old settings or ciphers. Poor configuration, use of weak keys, or exposed root login can create risks. There are also threats related to unauthorized port forwarding or use of known, stolen keys.
With SSL/TLS, risks include attempts to issue fraudulent certificates, use of expired certificates, or disabling of proper certificate checks in browsers or apps. Older SSL/TLS protocol versions contain known vulnerabilities. Both protocols are targets for attacks if not updated with secure settings.
Best Practices: Key/Certificate Management
For SSH, create unique key pairs for each user. Keys should have passphrases and never be stored in shared or unprotected locations. Password authentication should be disabled. Access should be limited to known key holders. Remove old or unused keys immediately.
For SSL/TLS, use certificates from trusted authorities. Monitor expiration dates. Only private servers should store the private key, and file permissions should prevent unauthorized access. Replace compromised certificates at once. Never share certificate private keys across servers or services.
Renewal and Revocation Methods
SSH keys are rotated manually, usually once or twice per year, or whenever staff changes. Remove old keys without delay. SSL/TLS certificate lifespans are set by their authority. Let’s Encrypt certificates need renewal every 90 days. Many hosting providers, including GreenGeeks, offer automatic renewal features. Revocation in SSL/TLS may use certificate revocation lists or the online status protocol, but not all browsers or systems check these each time.
Setup and Configuration on GreenGeeks
Enabling SSH Access via GreenGeeks Dashboard
On GreenGeeks hosting, SSH access is off by default. You can enable it in the hosting dashboard. Add your public SSH keys as needed and restrict connections by IP to reduce risk. Default access helps prevent unauthorized logins. You have options to adjust permissions or specify which accounts can authenticate.
Installing and Renewing SSL/TLS Certificates (Let’s Encrypt)
GreenGeeks includes Let’s Encrypt support in its dashboard. Certificates are free and renew automatically every 90 days. You can start installation, force certificate renewal, or upload custom certificates as needed. Tools are in the dashboard; minimal manual effort is needed for most SSL/TLS management.
Tips for Secure Key and Cert Storage
SSH private keys should stay on your computer, protected by a passphrase and secured using permission controls. Never email keys or store them in public cloud drives. SSL/TLS private keys should only be on your site’s web server, with owner-only permissions and regular encrypted backups. Avoid reusing the same key or certificate on multiple domains or systems.
Troubleshooting and Common Issues
SSH Connection Issues (Auth Failures, Timeouts)
Problems connecting by SSH often result from mismatched or missing keys, incorrect file permissions, server rebuilds that change host keys, or blocked connections due to firewalls. Use the command ssh -v to see details as the connection starts. Check directory and key file permissions on both client and server (~/.ssh should usually be 700, files like id_rsa set to 600). Server-side logs and config files are useful when troubleshooting.
SSL Warnings and Mixed-Content Errors
Broken SSL on a site can trigger browser warnings, such as “Not secure” or a failed padlock icon. Reasons include expired or mismatched certificates, not serving HTTPS for all site content (mixed content), or failed auto-renewal with Let’s Encrypt. If the certificate covers “example.com” but you visit “www.example.com,” it may not work. Browsers may block all or part of the site in these cases. Let’s Encrypt renewal errors often stem from DNS or web server rules that block certificate validation checks.
Tools for Diagnosis (ssh -v, SSL Labs, OpenSSL)
- Use ssh -v or ssh -vvv on the command line for SSH connection tracing.
- Use SSL Labs to scan your site’s SSL/TLS setup and get a detailed grade and security report.
- OpenSSL has commands to check certificates, test supported ciphers, and connect to remote servers to test SSL/TLS responses.
Choosing Between SSH and SSL/TLS
Decision Matrix Based on Needs
- For working directly on a server, always use SSH.
- For public websites and browser traffic, use SSL/TLS to secure those connections.
- For APIs and webhooks, SSL/TLS is standard. Only use SSH for server-to-server automation or code repository access.
- For file transfer, use SCP or SFTP (via SSH) for direct server file management. Use HTTPS if moving data between apps or sites.
When Both Are Needed Together
Some server tasks require both protocols. For example, you may use SSH to log in and set up a web application on a server, and then use SSL/TLS to secure access to that application’s website or API. This is common in web development and site deployment.
Checklist for GreenGeeks Users
- Enable SSH only if remote command-line control is needed. Always use key-based authentication instead of passwords.
- Turn on SSL/TLS for all domains, even if the site does not take logins or payments.
- Review and update your keys and certificates on a regular schedule. Revoke and replace them if staff changes or there is any sign of compromise.
- Check that all cipher suites, ports, and authentication methods in server settings use current security recommendations.
Final Takeaways
SSH and SSL/TLS secure different types of network traffic and should not be substituted for each other. SSH is made for direct server access and scripting. SSL/TLS is required for safe browser and API traffic. Both need proper setup and routine checks for reliable protection. Poor key and certificate management can create risks even on modern systems.
FAQs
1. Can I use SSL instead of SSH for remote access?
No. SSL/TLS secures websites and APIs but does not allow shell access or command execution on servers. Use SSH for remote command-line server access.
2. Do I need both SSH and SSL for a secure website?
Yes. You use SSH to manage the server. SSL/TLS secures the actual web traffic for site visitors.
3. What’s more secure: SSH keys or SSL certificates?
Both provide strong security if implemented correctly. SSH keys are highly resistant to guessing attacks. SSL certificates establish trusted web traffic. Each method protects a different channel.
4. How do I renew my SSL cert on GreenGeeks?
GreenGeeks uses Let’s Encrypt, which renews certificates automatically. Manual renewal or reissue options are also present in the dashboard.
5. Can SSH tunnels be used for HTTPS traffic?
Yes. SSH port forwarding can move HTTPS traffic securely through SSH, but this is an advanced process and not a replacement for setting up SSL/TLS on a web server.
6. How do I disable weak SSH algorithms?
Open the SSH server configuration file (sshd_config). Set only strong ciphers, MACs, and key exchange options. Restart SSH after testing the changes.
7. Why does my browser show “Not secure”?
The site does not have a current SSL/TLS certificate, has an expired or invalid certificate, or is loading insecure HTTP resources. Fix the certificate and switch all resources to HTTPS.
8. Should I enable SSH root login?
No. Always disable root login by SSH. Use non-root user accounts with sudo permissions as needed.
9. How often should I rotate SSH keys and SSL certs?
Update SSH keys at least once per year or any time team members change. Let’s Encrypt certificates renew every 90 days, and other certificates have set expiration dates.
10. Which tools help audit SSH and SSL configurations?
- For SSH: ssh-audit, nmap, manual review of config files.
- For SSL/TLS: SSL Labs online checker, OpenSSL command line tools, testssl.sh, or security panels in the hosting dashboard.
