How Certificate Transparency Logs Work

1. Certificate Request

• A website owner asks a trusted Certificate Authority (CA) for an SSL/TLS certificate.

• The CA verifies domain ownership and checks business credentials.

• After validation, the CA creates a pre‑certificate a preliminary version with all key details.

2. Logging the Pre‑certificate

• The CA submits the pre‑certificate to multiple independent CT logs.

• These logs are distributed globally to avoid a single point of control.

• Each log entry is permanent and tamper‑proof, forming a secure public ledger.

3. Getting a Signed Certificate Timestamp (SCT)

• Each log issues an SCT a cryptographic timestamp proving the pre‑certificate was logged at a specific time.

• The SCT acts like a digital receipt that's embedded into the final certificate.

• The timestamp is secure and cannot be forged or altered.

4. Browser Verification

• When a user visits the website, the browser checks the certificate’s SCTs against public CT logs in real time.

• If everything matches, the browser shows the padlock and establishes a secure connection.

• If the SCTs are missing or inconsistent, the browser warns the user.

5. Ongoing Monitoring by the Community

• Security researchers, domain owners, and browser vendors scan CT logs for suspicious certificates.

• They look for unauthorized certificates, policy violations, or malicious activity.

• Alerts are issued quickly when something seems off, ensuring swift corrective action.