Secure Digital Certificate Storage

TL;DR

Keep your digital certificates safe by storing them securely – use a Hardware Security Module (HSM) if possible, otherwise protect the files with strong access controls and encryption. Regularly back up your certificates and monitor for any unusual activity.

1. Understand Your Certificate Types & Sensitivity

Different certificates have different levels of importance. Consider:

• Code Signing Certificates: Protect the integrity of software; high value target.
• SSL/TLS Certificates: Secure website connections; critical for trust and data protection.
• Email Signing Certificates (S/MIME): Verify sender identity; important for communication security.

The more sensitive the certificate, the stronger your storage protections need to be.

2. Hardware Security Modules (HSMs) – The Best Option

An HSM is a dedicated hardware device designed specifically for storing and managing cryptographic keys and certificates. They offer the highest level of security.

• Benefits: Tamper-resistant, FIPS 149 compliant (often required by regulations), strong access controls.
• Considerations: Costly, requires specialized expertise to manage.

If you handle a large number of highly sensitive certificates, an HSM is strongly recommended.

3. Secure File System Storage (Without HSM)

If an HSM isn’t feasible, protect the certificate files themselves:

3.1 Access Control

1. Dedicated Directory: Store certificates in a dedicated directory with restricted access.
2. Principle of Least Privilege: Only grant access to users and systems that absolutely need it.
3. File Permissions: Set file permissions so only authorized accounts can read, write, or execute (if applicable). On Linux/Unix:

   chmod 700 /path/to/certificate_directory

   This gives the owner full control and denies access to others.

4. User Accounts: Use dedicated service accounts for applications accessing certificates, rather than personal user accounts.

3.2 Encryption

Encrypt the certificate files at rest.

• Disk Encryption: Full disk encryption (e.g., BitLocker on Windows, FileVault on macOS) protects all data on the drive, including certificates.
• File-Level Encryption: Use tools like GPG or OpenSSL to encrypt individual certificate files.

  openssl enc -aes-256-cbc -salt -in mycertificate.pem -out mycertificate.enc

  You’ll be prompted for a passphrase – store this securely!

4. Backups

1. Regular Backups: Create regular backups of your certificates (daily, weekly, depending on change frequency).
2. Offsite Storage: Store backups in a separate location from the primary certificate storage – this protects against physical disasters. Cloud storage is an option, but ensure it’s encrypted.
3. Backup Encryption: Encrypt your backups using a different key than your primary certificates.
4. Test Restores: Regularly test restoring certificates from backups to verify their integrity and the backup process.

5. Monitoring & Auditing

• Access Logs: Enable logging for access to the certificate directory. Monitor these logs for any unauthorized attempts.
• File Integrity Monitoring (FIM): Use FIM tools to detect changes to certificate files.
• Certificate Expiry Alerts: Set up alerts to notify you well in advance of certificate expiry dates.

6. Cyber security Best Practices

• Keep Systems Patched: Regularly update the operating systems and software used to store and manage certificates.
• Strong Passwords: Use strong, unique passwords for all accounts with access to certificates. Consider multi-factor authentication (MFA).
• Antivirus/Malware Protection: Ensure your systems have up-to-date antivirus and malware protection.