openssl.org

OpenSSL.org is a software package that provides a robust, commercial-grade toolkit for general-purpose cryptography and secure communication. It includes libssl, which implements TLS protocol versions, libcrypto, a general-purpose cryptographic library, and the openssl command line tool for various cryptographic tasks. It can be downloaded from the official website, and precompiled versions are available for different operating systems. Development and contributions are done through the OpenSSL repository on GitHub.