The wolfSSL embedded SSL library is a lightweight SSL/TLS library written in ANSI C and targeted for embedded, RTOS, and resource-constrained environments - primarily because of its small size, speed, and feature set.  It is commonly used in standard operating environments as well because of its royalty-free pricing and excellent cross-platform support.  wolfSSL supports industry standards up to the current TLS 1.3 and DTLS 1.2 levels, is up to 20 times smaller than OpenSSL, and offers progressive ciphers such as ChaCha20, Curve25519, NTRU, and Blake2b.  User benchmarking and feedback reports dramatically better performance when using wolfSSL over OpenSSL. wolfSSL is powered by the wolfCrypt library. A version of the wolfCrypt cryptography library has been FIPS 140-2 validated (Certificate #2425 and#3389). Highlights

• Up to TLS 1.3 and DTLS 1.2
• Full client and server support
• Progressive list of supported ciphers
• Key and Certificate generation
• OCSP, CRL support
• Commercially supported

Lightweight

• Small size: 20-100kB
• Runtime memory: 1-36kB
• 20x smaller than OpenSSL

Portable

• Abstraction Layers (OS, Custom I/O, Standard C library, and more)
• Simple API
• OpenSSL Compatibility Layer
• The long list of supported platforms