In a context where digital exchanges are at the core of business processes, securing application traffic and APIs is no longer optional but an operational requirement.
This article explains to CISOs, CIOs, and security leaders why the TLS protocol and strict management of X.509 certificates are foundational components of any cybersecurity strategy.

We detail the technical principles (authentication, encryption, integrity), configuration best practices (versions, cipher suites, forward secrecy), and the operational steps to deploy and maintain a reliable chain of trust.
Finally, we show how to automate the inventory, renewal, and monitoring of certificates to reduce business risks and ensure compliance.

Important terminology note: the historical term “SSL certificate” is commonly used but inaccurate.
Modern certificates are X.509 certificates, and the secure protocol in use is TLS (Transport Layer Security).
SSL versions (SSL 2.0/3.0) are obsolete and must not be used.
In this article, we therefore refer to TLS and X.509 certificates.

What Is an X.509 Certificate?

An X.509 certificate is a digital file that binds a public key to an identity (domain name, organization).
It is issued and signed by a Certificate Authority (CA) and contains:

• Subject name (domain),
• Public key,
• Validity period,
• Signature algorithm,
• CA signature.

Technically, it enables three key functions during a TLS connection:

• Authentication – the server proves its identity
• Confidentiality – encrypted channel for data exchange
• Integrity – detection of tampering or alteration

Security relies on a chain of trust: server certificate → intermediate certificates → root certificate.
Missing intermediate certificates or an incomplete chain causes client-side validation errors.

Types of X.509 Certificates

Certificates differ by validation level and scope:

• DV (Domain Validation) – verifies only domain ownership. Fast issuance, ensures encryption but not organization identity. Suitable for blogs, small sites, or platforms without sensitive data.
• OV (Organization Validation) – validates both the domain and the organization through official documents, providing higher credibility. Recommended for companies collecting non-critical customer data.
• EV (Extended Validation) – highest level of trust with strict legal and operational checks, often displaying the organization name in the browser. Essential for e-commerce, financial institutions, or any service handling highly sensitive information.

Other practices/formats:

• Wildcard – covers all subdomains of a domain.
• SAN / Multi-domain – covers multiple domains in a single certificate.

All of these remain X.509 certificates — the term “SSL certificate” is a historical misnomer.

TLS vs SSL: Differences and Recommended Versions

SSL is deprecated and replaced by TLS due to security vulnerabilities.
Current recommendations:

• TLS 1.3 – preferred (faster, stronger encryption, fewer handshake steps)
• TLS 1.2 – acceptable with strong configuration (modern cipher suites, ECDHE for forward secrecy)
• TLS < 1.2 (and SSL) – obsolete and insecure; disable on servers.

Technical key points:

• Enable ECDHE for forward secrecy.
• Prefer AES-GCM or CHACHA20-POLY1305 over legacy algorithms (e.g., RC4, weak CBC).
• Implement OCSP stapling to speed up revocation checks.
• Use Certificate Transparency and certificate monitoring.

Why TLS and X.509 Certificates Are Critical for Cybersecurity

• Confidentiality – encrypts data in transit to prevent interception (man-in-the-middle attacks).
• Integrity – protects against tampering of data during transmission.
• Authenticity – ensures users connect to the intended service.
• Operational trust – mitigates legal and reputational risks from leaks or impersonation.
• Compliance – required by frameworks such as ISO 27001, ANSSI guidelines, and industry regulations.
• Service availability – misconfigured TLS (obsolete versions, incomplete chains, expired certs) can cause outages.

For CISOs and CIOs, TLS is a non-negotiable component of application and API security.

How to Deploy an X.509 Certificate and Robust TLS Configuration

Recommended operational steps:

1. Choose certificate type (DV/OV/EV) and scope (SAN, wildcard).
2. Generate a CSR (Certificate Signing Request) on the server or internal PKI with a secure private key (RSA ≥ 2048 bits or ECDSA P-256/P-384).
3. Order / Issue – obtain the certificate from a trusted CA (e.g., DigiCert, Let’s Encrypt, Sectigo).
4. Install the server and intermediate certificates – the chain must be complete for client validation.
5. Configure TLS – enforce TLS 1.2+ (prefer TLS 1.3), enable ECDHE, use modern cipher suites, disable SSL/TLS < 1.2.
6. Test the configuration using SSL Labs, Mozilla Observatory, or internal scans to verify cipher suites, forward secrecy, and chain completeness.
7. Enable HSTS and OCSP stapling.
8. Automate renewals (e.g., Let’s Encrypt with ACME) to prevent unexpected expiration.
9. Monitor expiration, revocation (OCSP/CRL), and anomalies in Certificate Transparency logs.
10. Plan key rotation and revocation in case of private key compromise.

Practical checks:

• Ensure CN/SAN matches the domain.
• Avoid duplicate or incorrect certificates on multiple endpoints.
• Maintain a key-rotation schedule and PKI governance if applicable.

Cryptographic & Operational Best Practices

• Key length: RSA ≥ 2048 bits (3072+ for long-term), or ECDSA P-256/P-384.
• Signatures: SHA-256 or stronger.
• Cipher suites: AEAD only (AES-GCM, CHACHA20-POLY1305).
• Forward secrecy: mandatory (ECDHE).
• TLS 1.3: use whenever supported.
• Monitoring: centralized inventory, expiration alerts, configuration audits.

How Board of Cyber Helps Secure Your Exchanges

Board of Cyber streamlines certificate governance and TLS quality through:

• Automatic certificate inventory (servers, APIs, appliances) with expiration and algorithm tracking.
• Continuous monitoring of TLS versions, cipher suites, and detection of endpoints allowing TLS < 1.2.
• Alerting for upcoming expirations, incomplete chains, or revoked certificates.
• Third-party evaluation – continuous scoring of partner TLS configurations (TPRM) to secure inter-organizational exchanges.
• Dashboards & compliance – consolidated metrics (% of services running TLS 1.3, % with forward secrecy) aligned with ISO, ANSSI, and DORA requirements.

These features automate renewals, prioritize remediation, and simplify compliance audits.

Conclusion

To effectively secure digital communications, deploying TLS (v 1.2 or ideally v 1.3) and rigorously managing X.509 certificates is essential.
Beyond encryption, this means maintaining a complete chain of trust, strong configurations resistant to modern attacks, and operational processes for inventory, renewal, and monitoring.

Adopting a governance and monitoring solution — such as Board of Cyber — transforms certificate and TLS management into an automated, auditable, and compliant process.