SSH Keys vs SSH Passwords: A Comprehensive Comparison for Enhanced Security

When discussing the security of authentication mechanisms, SSH keys and SSH passwords are often compared. While password authentication has been in use for decades, its efficiency and ease of implementation have made it a familiar choice. However, modern enterprises are increasingly adopting SSH keys for their robust security features. This article delves into the advantages and challenges of using SSH keys versus passwords, with a particular emphasis on security benefits and practical considerations.

Security Benefits of SSH Keys

The security benefits of SSH key-based access are often overlooked by many companies. SSH keys provide a more resilient and secure authentication method compared to passwords, which are frequently targeted by cyber attacks. Key-based authentication offers several advantages:

Reduced risk of keylogging and server compromise: Unlike passwords, which can be captured by keyloggers or compromised servers, SSH keys are significantly less vulnerable to such attacks. This makes them a preferred choice for securing sensitive systems.

Granular access control: SSH keys can be restricted to specific domains, addresses, or even certain commands. This granular control ensures that access is confined to necessary resources and operations, enhancing overall security.

Audit trails: With OpenSSH server verbose logging, the key fingerprint can be captured, providing an audit trail. This is invaluable for detecting unauthorized access and managing multiple users with access.

Challenges with SSH Keys

Despite their security benefits, SSH keys also present unique challenges that must be addressed:

Change Management Nightmare

Without proper control, SSH key access can become a significant nightmare. For instance, configurations in SSH server setups often do not prevent the unauthorized creation of key authorizations. These authorizations could bypass centralized methods of controlling access, leading to potential security breaches.

This lack of control creates a scenario where someone could create unauthorized access without tracking or approvals, making it difficult to manage and enforce security policies effectively.

Un-managed SSH Key Access

Un-managed SSH key access can lead to retained key authorizations that should no longer be active. A real-world example includes a former system administrator who took their private key with them when they left the company. If their public key was not removed from the end hosts, this former employee could still gain access to the systems even though they no longer work there.

Compliance Considerations

Compliance requirements often mandate that SSH keys be managed just as rigorously as passwords. Regulations like PCI DSS, HIPAA, and MAS clearly indicate that proper management of SSH keys is necessary to meet compliance standards. This includes key rotation, removing old and unused access, and implementing separation of duties, especially when granting access to production environments.

Manual Management Costs

The manual process of managing SSH keys can be resource-intensive and costly. Third-party guidelines, such as those used by the US Federal Government, provide excellent guidance on how to efficiently and securely manage SSH keys. These guidelines emphasize the importance of implementing best practices, such as key rotation and proper lifecycle management, to ensure ongoing security and compliance.

Real-World Example and Best Practices

Based on personal experience, I highly recommend using SSH keys whenever possible and blocking password access for the root account. OpenSSH server settings can be configured to allow verbose logging, which captures the key fingerprint and reveals which key was used to log in. This provides valuable audit trails and accountability.

While there is a risk of extending trust through poor key discipline, the balance is generally tipped in favor of using keys. The risk of someone creating a key with no passphrase and leaving it on an unsecured device can be mitigated by other security measures. Compared to default passwords in IoT devices or well-known passwords like “123456,” the potential harm from an SSH key breach is less immediate and easier to address.

Ultimately, the security benefits of SSH keys far outweigh the challenges if managed properly. Ensuring rigorous key management practices, thorough compliance adherence, and robust change controls are essential for leveraging the full potential of SSH key-based authentication.