Certificate Transparency

Certificate Transparency (CT) is an Internet security standard for monitoring and auditing the issuance of digital certificates. When an internet user interacts with a website, a trusted third party is needed for assurance that the website is legitimate and that the website's encryption key is valid. This third party, called a certificate authority (CA), will issue a certificate for the website that the user's browser can validate. The security of encrypted internet traffic depends on the trust that certificates are only given out by the certificate authority and that the certificate authority has not been compromised. Certificate Transparency makes public all issued certificates in the form of a distributed ledger, giving website owners and auditors the ability to detect and expose inappropriately issued certificates. Work on Certificate Transparency first began in 2011 after the certificate authority DigiNotar became compromised and started issuing malicious certificates. Google engineers submitted a draft to the Internet Engineering Task Force (IETF) in 2012. This effort resulted in IETF RFC 6962, a standard defining a system of public logs to record all certificates issued by publicly trusted certificate authorities, allowing efficient identification of mistakenly or maliciously issued certificates.