OpenSSL Library

OpenSSL is a robust, commercial-grade, full-featured toolkit for general-purpose cryptography and secure communication, implementing the TLS (Transport Layer Security) protocol and providing a general-purpose cryptography library. Maintained by the OpenSSL Project under the Apache Software Foundation umbrella since 2017 (transferred from OpenSSL Software Foundation), OpenSSL is one of the most critical pieces of internet infrastructure, used by Apache, NGINX, Postfix, cURL, and countless other applications for HTTPS, SMTPS, FTPS, and other encrypted protocols. The toolkit consists of three main components: libssl (the TLS library implementing TLS 1.0 through 1.3, DTLS, and legacy SSL protocols, with TLS 1.3 support since version 1.1.1), libcrypto (the cryptography library providing symmetric ciphers like AES-128/192/256 in GCM/CBC/CTR modes, ChaCha20-Poly1305, Camellia; asymmetric algorithms including RSA, DSA, DH, ECDH, ECDSA with curves like P-256, P-384, Curve25519; hash functions SHA-1/256/384/512, SHA-3, BLAKE2/3, MD5; MAC algorithms HMAC, CMAC, GMAC; key derivation PBKDF2, scrypt, HKDF; random number generation; X.509 certificate management; PKCS standards), and the openssl command-line tool (for generating keys, creating certificate signing requests, managing certificates, testing TLS connections, and benchmarking cryptographic operations). OpenSSL 3.0+ introduced a provider architecture for cryptographic algorithm loading.