A commonly-used protocol for managing the security of a transmission of a message transmission. SSL uses the public-and-private key encryption system from RSA, which also includes the use of a digital certificate. SSL was the de facto standard until it evolved into Transport Layer Security (TLS). For more information on TLS, see TLS in the Glossary. TLS 1.0 and SSL are disallowed in some protocols, such as PCI-DSS, as of June 30, 2018 for TLS 1.0.