OpenSSL

OpenSSL is a widely used open-source software library that provides cryptographic functions and implements the SSL and TLS protocols. It is written in C and includes two main components: libssl, which implements the TLS/SSL protocols and higher-level key management, and libcrypto, which provides cryptographic primitives used by other software. The project also ships the OpenSSL command-line tool, used for generating keys and certificates, converting formats, and performing cryptographic tests.

OpenSSL originated from the SSLeay project by Eric A. Young and Tim J. Hudson and was continued as OpenSSL in the late 1990s. It is maintained by the OpenSSL Project and a global community of contributors, with releases that include security advisories and patches. The library is cross-platform and widely deployed in web servers, application servers, email transfer agents, and clients. It is widely regarded as the de facto standard for securing communications, notably implementing the TLS protocol used by HTTPS.

Licensing and governance: OpenSSL is distributed under a permissive license model, historically including the OpenSSL License and the SSLeay License, with guidance to verify current terms. The project emphasizes security, providing periodic fixes and vulnerability advisories, and maintains compatibility with a broad range of operating systems and compiler environments. As an open-source project, OpenSSL relies on community contributions as well as commercial support from various vendors.