WolfSSL

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wolfSSL
Developer(s)	Todd Ouska
Initial release	February 19, 2006 (2006-02-19)[1]
Stable release	5.8.2[2]  / 17 July 2025
Repository	github.com/wolfssl/wolfssl
Written in	C
Operating system	Multi-platform
Type	Cryptography library
License	GPL-2.0-or-later or proprietary[3]
Website	www.wolfssl.com

wolfSSL 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, 1.2, and 1.3) written in the C programming 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.^[4][5]

wolfSSL is currently available for Microsoft Windows, Linux, macOS, Solaris, ESP32, ESP8266, ThreadX, VxWorks, FreeBSD, NetBSD, OpenBSD, embedded Linux, Yocto Project, OpenEmbedded, WinCE, Haiku, OpenWrt, iPhone, Android, Wii, and GameCube through DevKitPro support, QNX, MontaVista, Tron variants, NonStop OS, OpenCL, Micrium's MicroC/OS-II, FreeRTOS, SafeRTOS, Freescale MQX, Nucleus, TinyOS, TI-RTOS, HP-UX, uTasker, uT-kernel, embOS, INtime, mbed, RIOT, CMSIS-RTOS, FROSTED, Green Hills INTEGRITY, Keil RTX, TOPPERS, PetaLinux, Apache Mynewt, and PikeOS.^[6]

The genesis of wolfSSL dates to 2004. OpenSSL was available at the time, and was dual licensed under the OpenSSL License and the SSLeay license.^[7] yaSSL, alternatively, was developed and dual-licensed under both a commercial license and the GPL.^[8] yaSSL offered a more modern API, commercial style developer support and was complete with an OpenSSL compatibility layer.^[4] The first major user of wolfSSL/CyaSSL/yaSSL was MySQL.^[9] Through bundling with MySQL, yaSSL has achieved extremely high distribution volumes in the millions.

In February 2019, Daniel Stenberg, the creator of cURL, was hired by the wolfSSL project to work on cURL.^[10]

The wolfSSL lightweight SSL library implements the following protocols:^[11]

• SSL 3.0, TLS 1.0, TLS 1.1, TLS 1.2, TLS 1.3
• DTLS 1.0, DTLS 1.2, DTLS 1.3
• Extensions: Server Name Indication (SNI), Maximum Fragment Length, Truncated HMAC, Application Layer Protocol Negotiation (ALPN), Extended Master Secret
• Ciphersuites: TLS Secure Remote Password, TLS Pre-Shared Key
• Post-quantum cryptography: ML-DSA added to sigAlgs, ML-KEM added to Supported Groups, QSH (deprecated and removed)
• Public Key Cryptography Standards:
  • PKCS #1 - RSA Cryptography
  • PKCS #3 - Diffie-Hellman Key Agreement
  • PKCS #5 - Password-Based Encryption
  • PKCS #7 - Cryptographic Message Syntax (CMS)
  • PKCS #8 - Private-Key Information Syntax
  • PKCS #9 - Selected Attribute Types
  • PKCS #10 - Certificate signing request (CSR)
  • PKCS #11 - Cryptographic Token Interface
  • PKCS #12 - Certificate/Personal Information Exchange Syntax Standard

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.^[12]

wolfSSL uses the following cryptography libraries:

By default, wolfSSL uses the cryptographic services provided by wolfCrypt.^[13] wolfCrypt Provides RSA, ECC, DSS, Diffie–Hellman, EDH, NTRU (deprecated and removed), DES, Triple DES, AES (CBC, CTR, CCM, GCM), Camellia, IDEA, ARC4, HC-128, ChaCha20, MD2, MD4, MD5, SHA-1, SHA-2, SHA-3, BLAKE2, RIPEMD-160, Poly1305, Random Number Generation, Large Integer support, base 16/64 encoding/decoding, and post-quantum cryptographic algorithms: ML-KEM (certified under FIPS 203) and ML-DSA (certified under FIPS 204).

wolfCrypt also includes support for the recent X25519 and Ed25519 algorithms.

wolfCrypt acts as a back-end crypto implementation for several popular software packages and libraries, including MIT Kerberos^[14] (where it can be enabled using a build option).

CyaSSL+ includes NTRU^[15] public key encryption. The addition of NTRU in CyaSSL+ was a result of the partnership between yaSSL and Security Innovation.^[15] 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.

wolfSSL supports the following Secure Elements:

• STMicroelectronics STSAFE
• Microchip CryptoAuthentication ATECC508A
• NXP EdgeLock SE050 Secure Element

wolfSSL supports the following hardware technologies:

• Intel SGX (Software Guard Extensions) ^[16] - Intel SGX allows a smaller attack surface and has been shown to provide a higher level of security for executing code without a significant impact on performance.

wolfSSL is dual licensed:

• Licensed under the GPL-2.0-or-later license. This is good for GPL open source projects and evaluation.
• Licensed under a commercial non-GPL license. This comes with additional support and maintenance packages and is priced at 7,500 USD per product or SKU as of 2025.

• Transport Layer Security
• Comparison of TLS implementations
• Comparison of cryptography libraries
• GnuTLS
• Network Security Services
• OpenSSL

• wolfSSL/CyaSSL Homepage
• wolfSSL Now With ChaCha20 and Poly1305