SSLeay

SSLeay was a free software cryptographic library that implemented the Secure Sockets Layer (SSL) protocol and its successor Transport Layer Security (TLS) for securing communications over computer networks. It was developed by Eric A. Young and Tim J. Hudson and first released in 1995. The project encompassed two main components: libssl, which provided the SSL/TLS protocol implementation, and libcrypto, a general-purpose cryptographic library that offered primitives such as symmetric ciphers, public-key algorithms, and digests used by applications built on top of it.

SSLeay was distributed under the SSLeay License, a permissive open-source license. The library gained broad adoption in the late 1990s and formed the basis for many secure communication implementations used by web servers, clients, and other network software. In 1998–1999, the SSLeay project was effectively superseded by OpenSSL, a fork and expansion of the codebase maintained by a broader community. The OpenSSL project adopted a dual-licensing approach that included the original SSLeay license alongside the OpenSSL license, and it continued development of the library under the name OpenSSL.

Legacy: The SSLeay codebase and its OpenSSL successor were influential in the standardization and adoption of TLS in web infrastructure. OpenSSL remains a central component of many secure communications stacks, though current best practices recommend newer TLS libraries for new projects.