OpenSSL is an open-source implementation of the SSL (Secure Sockets Layer) and TLS (Transport Layer Security) protocols. It provides a robust, full-featured library for implementing secure communications over computer networks.
OpenSSL includes tools for generating RSA private keys, creating CSRs (Certificate Signing Requests), and managing certificates and certificate authorities. It also supports various cryptographic algorithms, such as encryption, decryption, and message digests.