wolfSSL (formerly CyaSSL or yet another SSL) is a small, portable, embedded SSL/TLS library targeted for use by embedded systems developers. It is an open source implementation of TLS (SSL 3.0, TLS 1.0, 1.1, 1.2, 1.3, and DTLS 1.0 and 1.2) written in the C language. It includes SSL/TLS client libraries and an SSL/TLS server implementation as well as support for multiple APIs, including those defined by SSL and TLS. wolfSSL also includes an OpenSSL compatibility interface with the most commonly used OpenSSL functions.[3]
A predecessor of wolfSSL, yaSSL is a C++ based SSL library for embedded environments and real time operating systems with constrained resources.
The genesis of yaSSL, or yet another SSL, dates to 2004. OpenSSL was available at the time, and was dual licensed under the OpenSSL License and the SSLeay license.[4] yaSSL, alternatively, was developed and dual-licensed under both a commercial license and the GPL.[5] yaSSL offered a more modern API, commercial style developer support and was complete with an OpenSSL compatibility layer.[3] The first major user of wolfSSL/CyaSSL/yaSSL was MySQL.[6] Through bundling with MySQL, yaSSL has achieved extremely high distribution volumes in the millions.
The wolfSSL lightweight SSL library implements the following protocols:[7]
SSL 3.0, TLS 1.0, TLS 1.1, TLS 1.2, TLS 1.3
DTLS 1.0, DTLS 1.2
Protocol Notes:
SSL 2.0 - SSL 2.0 was deprecated (prohibited) in 2011 by RFC 6176. wolfSSL does not support it.
SSL 3.0 - SSL 3.0 was deprecated (prohibited) in 2015 by RFC 7568. In response to the POODLE attack, SSL 3.0 has been disabled by default since wolfSSL 3.6.6, but can be enabled with a compile-time option.[8]
Algorithms
wolfSSL uses the following cryptography libraries:
wolfCrypt also includes support for the recent Curve25519 and Ed25519 algorithms.
wolfCrypt acts as a back-end crypto implementation for several popular software packages and libraries, including MIT Kerberos[10] (where it can be enabled using a build option).
NTRU
CyaSSL+ includes NTRU[11] public key encryption. The addition of NTRU in CyaSSL+ was a result of the partnership between yaSSL and Security Innovation.[11] NTRU works well in mobile and embedded environments due to the reduced bit size needed to provide the same security as other public key systems. In addition, it's not known to be vulnerable to quantum attacks. Several cipher suites utilizing NTRU are available with CyaSSL+ including AES-256, RC4, and HC-128.
SGX
wolfSSL supports use of Intel SGX (Software Guard Extensions[12][better source needed]). Intel SGX allows for a smaller attack surface area and has been shown to provide a higher level of security for executing code without a significant negative impact on performance.
