The protocol used to establish secure communication over the internet is Secure Sockets Layer (SSL) or its successor, Transport Layer Security (TLS). These cryptographic protocols encrypt data exchanged between clients and servers, ensuring that sensitive information remains confidential and protected from eavesdropping and tampering. SSL/TLS certificates validate the identities of parties involved, further enhancing security. These protocols are fundamental to enabling secure online transactions and protecting user data in various applications, including websites and email communications.