Internet and computer basics

Certificate authority (CA)

An organization that issues the digital certificates that websites and other services use to prove who they are, a bit like an office that issues ID cards. Browsers and phones keep a list of the certificate authorities they trust. If the secret key a certificate authority signs certificates with (a long secret number) gets out, anyone can make fake certificates, pass off a fake site as the real one, or read traffic through a man-in-the-middle attack. In October 2026 the secret keys of eight certificates of eMudhra, a certificate authority in India, turned out to be so weak that anyone could work them out. Browser makers quickly blocked them, and eMudhra said it would stop issuing certificates for websites worldwide.