# WolfSSL

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Implementation of TLS protocols

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wolfSSL Developer Todd Ouska Release February 19, 2006 (2006-02-19)[1] Stable release 5.9.2[2] / 25 June 2026 Written in C Operating system Multi-platform Type Cryptography library License GPL-3.0-or-later or proprietary[3] Website www.wolfssl.com Repository github.com/wolfssl/wolfssl

**wolfSSL** is a small, portable, embedded SSL/TLS library targeted for use by embedded systems developers. It is an [open source](/source/Open-source_software) implementation of [TLS](/source/Transport_Layer_Security) (SSL 3.0, TLS 1.0, 1.1, 1.2, 1.3, and [DTLS](/source/Datagram_Transport_Layer_Security) 1.0, 1.2, and 1.3) written in the [C programming language](/source/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](/source/Secure_Sockets_Layer) and [TLS](/source/Transport_Layer_Security). wolfSSL also includes an [OpenSSL](/source/OpenSSL) compatibility interface with the most commonly used OpenSSL functions.[4][5]

## Platforms

wolfSSL is currently available for [Microsoft Windows](/source/Microsoft_Windows), [Linux](/source/Linux), [macOS](/source/MacOS), [Solaris](/source/Solaris_(operating_system)), [ESP32](/source/ESP32), [ESP8266](/source/ESP8266), [ThreadX](/source/ThreadX), [VxWorks](/source/VxWorks), [FreeBSD](/source/FreeBSD), [NetBSD](/source/NetBSD), [OpenBSD](/source/OpenBSD), [embedded Linux](/source/Embedded_Linux), [Yocto Project](/source/Yocto_Project), [OpenEmbedded](/source/OpenEmbedded), [WinCE](/source/WinCE), [Haiku](/source/Haiku_os), [OpenWrt](/source/OpenWrt), [iPhone](/source/IPhone), [Android](/source/Android_(operating_system)), [Wii](/source/Wii), and [GameCube](/source/GameCube) through DevKitPro support, [QNX](/source/QNX), [MontaVista](/source/MontaVista), [Tron](/source/TRON_Project) variants, [NonStop OS](/source/NonStop_OS), [OpenCL](/source/OpenCL), Micrium's [MicroC/OS-II](/source/MicroC%2FOS-II), [FreeRTOS](/source/FreeRTOS), [SafeRTOS](/source/SafeRTOS), [Freescale MQX](/source/MQX), [Nucleus](/source/Nucleus_RTOS), [TinyOS](/source/TinyOS), [TI-RTOS](/source/TI-RTOS), [HP-UX](/source/HP-UX), uTasker, uT-kernel, embOS, [INtime](/source/INtime), [mbed](/source/Mbed), [RIOT](/source/RIOT_(operating_system)), CMSIS-RTOS, FROSTED, [Green Hills INTEGRITY](/source/Integrity_(operating_system)), Keil RTX, TOPPERS, PetaLinux, [Apache Mynewt](/source/Apache_Mynewt), and [PikeOS](/source/PikeOS),[6] Deos, Azure Sphere OS, Zephyr, AIX, and Cesium.

## History

The genesis of wolfSSL dates to 2004. [OpenSSL](/source/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](/source/MySQL).[9] Through bundling with MySQL, yaSSL has achieved extremely high distribution volumes in the millions.

In February 2019, [Daniel Stenberg](/source/Daniel_Stenberg), the creator of [cURL](/source/CURL), was hired by the wolfSSL project to work on cURL.[10]

## Protocols

Main article: [Transport Layer Security](/source/Transport_Layer_Security)

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](/source/Server_Name_Indication) (SNI), Maximum Fragment Length, Truncated [HMAC](/source/HMAC), [Application Layer Protocol Negotiation](/source/Application_Layer_Protocol_Negotiation) (ALPN), Extended Master Secret, Supported Elliptic Curves

- Ciphersuites: [TLS Secure Remote Password](/source/TLS-SRP), [TLS Pre-Shared Key](/source/TLS-PSK)

- [Post-quantum cryptography](/source/Post-quantum_cryptography): ML-DSA added to sigAlgs, ML-KEM added to Supported Groups, QSH (deprecated and removed), Dual Algorithm Certificate, and TLS 1.3 Dual Algorithm Authentication Support

- Hybrid TLS Key Establishment Schemes: - ECDHE P-256 with Kyber Level 1 - ECDHE P-384 with Kyber Level 3 - ECDHE P-521 with Kyber Level 5

- [Public Key Cryptography Standards](/source/PKCS): - [PKCS #1](/source/PKCS_1) - [RSA Cryptography](/source/RSA_(cryptosystem)) - PKCS #3 - [Diffie-Hellman Key Agreement](/source/Diffie-Hellman_key_exchange) - PKCS #5 - [Password-Based Encryption](/source/Password-based_cryptography) - [PKCS #7](/source/PKCS_7) - [Cryptographic Message Syntax](/source/Cryptographic_Message_Syntax) (CMS) - [PKCS #8](/source/PKCS_8) - Private-Key Information Syntax - PKCS #9 - Selected Attribute Types - [PKCS #10](/source/PKCS_10) - [Certificate signing request](/source/Certificate_signing_request) (CSR) - [PKCS #11](/source/PKCS_11) - Cryptographic Token Interface - [PKCS #12](/source/PKCS_12) - Certificate/Personal Information Exchange Syntax Standard

- QUIC support

- OCSP, OCSP Stapling, CRL

- HPKE (Hybrid Public Key Encryption)

- ECH (Encryption Client Hello)

- x.509v3 Certificates

- Mutual authentication

**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](/source/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]

## Algorithms

wolfSSL uses the following cryptography libraries:

### wolfCrypt

By default, wolfSSL uses the cryptographic services provided by wolfCrypt.[13] wolfCrypt Provides [RSA](/source/RSA_(algorithm)), [DSA](/source/Digital_Signature_Algorithm), [ECC](/source/Elliptic_curve_cryptography), [DSS](/source/Digital_Signature_Algorithm), [Diffie–Hellman](/source/Diffie%E2%80%93Hellman_key_exchange), [EDH](/source/Error_Detection_and_Handling), ECDH-ECDSA, ECDHE-ECDSA, ECDH-RSA, ECDHE-RSA, [NTRU](/source/NTRU) (deprecated and removed), [DES](/source/Data_Encryption_Standard), [Triple DES](/source/Triple_DES), [AES](/source/Advanced_Encryption_Standard) (CBC, CTR, CCM, GCM, OFB, XTS, GMAC, CMAC), [Camellia](/source/Camellia_(cipher)), [IDEA](/source/International_Data_Encryption_Algorithm), [ARC4](/source/ARC4), [HC-128](/source/HC-128), [ChaCha20](/source/ChaCha20), [MD2](/source/MD2_(cryptography)), [MD4](/source/MD4), [MD5](/source/MD5), [SHA-1](/source/SHA-1), [SHA-2](/source/SHA-2), [SHA-3](/source/SHA-3), [BLAKE2](/source/BLAKE_(hash_function)), [RIPEMD-160](/source/RIPEMD-160), [Poly1305](/source/Poly1305), SM2, [SM3](/source/SM3_(hash_function)), [SM4](/source/SM4_(cipher)) Random Number Generation, Large Integer support, base 16/64 encoding/decoding, [HMAC](/source/HMAC), [PBKDF2](/source/PBKDF2), and post-quantum cryptographic algorithms: [ML-KEM](/source/ML-KEM) (certified under FIPS 203) and ML-DSA (certified under FIPS 204).

- ECC curve types: SECP, SECPR2, SECPR3, BRAINPOOL, KOBLITZ

- ECC key lengths: 112, 128, 160, 192, 224, 239, 256, 320, 384, 512, 521

wolfCrypt also includes support for the [X25519](/source/X25519) and [Ed25519](/source/Ed25519) algorithms, as well as the [X448](/source/X448) and [Ed448](/source/Ed448) algorithms..

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

wolfCrypt is [FIPS](/source/Federal_Information_Processing_Standards) validated and holds two [FIPS 140-2](/source/FIPS_140-2) certificates (#2425[15] and #3389[16]) and two [FIPS 140-3](/source/FIPS_140-3) certificates (#4718[17] and #5041[18]).

### NTRU

CyaSSL+ includes [NTRU](/source/NTRUEncrypt)[19] public key encryption. The addition of NTRU in CyaSSL+ was a result of the partnership between yaSSL and Security Innovation.[19] 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.

## Post-Quantum

wolfSSL provides support for a range of post-quantum cryptographic algorithms, including the Kyber Key Encapsulation Mechanism (KEM), hybridized with NIST-recommended ECC curves to maintain FIPS compliance. Supported ML-KEM levels include Level 1 (ML-KEM-512), Level 3 (ML-KEM-768), and Level 5 (ML-KEM-1024). For digital signatures, wolfSSL implements ML-DSA at Levels 2, 3, and 5; FALCON at Levels 1 and 5; and SLH-DSA, LMS/HSS, and XMSS/XMSS^MT. The library also supports hybrid TLS key exchange schemes, combining ECDHE with ML-KEM at corresponding security levels as well as dual-algorithm certificates and TLS 1.3 dual-algorithm authentication.

## Hardware Integration

### Secure Element Support

wolfSSL supports the following [Secure Elements](/source/Secure_element):

- [STMicroelectronics](/source/STMicroelectronics) STSAFE

- [Microchip](/source/Microchip_Technology) CryptoAuthentication ATECC508A

- Microchip TA100

- [NXP](/source/NXP_Semiconductors) EdgeLock SE050 Secure Element

### Technology Support

wolfSSL supports the following hardware technologies:

- [Intel](/source/Intel) SGX ([Software Guard Extensions](/source/Software_Guard_Extensions)) [20] - 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.

- [NXP](/source/NXP_Semiconductors) CAAM (Cryptographic Acceleration and Assurance Module) on i.MX6 (QNX), i.MX8 (QNX/Linux), RT1170 FreeRTOS

- ARM TrustZone CryptoCell 310

- MAXQ1065/1080 RNG

- MAX32665 and MAX32666 TPU (Trust Protection Unit)

## Licensing

wolfSSL is dual licensed: under both the [GPL-3.0-or-later](/source/GNU_General_Public_License) license and commercial licensing.

## See also

- [Free and open-source software portal](https://en.wikipedia.org/wiki/Portal:Free_and_open-source_software)

- [Transport Layer Security](/source/Transport_Layer_Security)

- [Comparison of TLS implementations](/source/Comparison_of_TLS_implementations)

- [Comparison of cryptography libraries](/source/Comparison_of_cryptography_libraries)

- [GnuTLS](/source/GnuTLS)

- [Network Security Services](/source/Network_Security_Services)

- [OpenSSL](/source/OpenSSL)

## References

1. **[^](#cite_ref-wolfSSL-ChangeLog_1-0)** ["wolfSSL ChangeLog"](https://www.wolfssl.com/wolfSSL/Docs-wolfssl-changelog.html). 10 August 2017.

1. **[^](#cite_ref-wikidata-91b0c8febb4f573ccbb774ebc098ac8fbd29756f-v20_2-0)** ["Release 5.9.2"](https://github.com/wolfSSL/wolfssl/releases/tag/v5.9.2-stable). 25 June 2026. Retrieved 26 June 2026.

1. **[^](#cite_ref-LICENSING_3-0)** ["LICENSING"](https://github.com/wolfSSL/wolfssl/blob/master/LICENSING). *[GitHub](/source/GitHub)*.

1. ^ [***a***](#cite_ref-compatibility_4-0) [***b***](#cite_ref-compatibility_4-1) [wolfSSL – Embedded Communications Products](https://www.wolfssl.com/wolfSSL/Products.html)

1. **[^](#cite_ref-5)** ["What You Need to Know About the TLS 1.3 Protocol and wolfSSL's SSL/TLS Libraries"](https://www.allaboutcircuits.com/news/what-you-need-to-know-about-the-tls-1.3-protocol-and-wolfssls-ssl-tls-libra/). *www.allaboutcircuits.com*. Retrieved 2018-12-28.

1. **[^](#cite_ref-6)** ["wolfSSL Embedded SSL/TLS Library | wolfSSL Products"](https://www.wolfssl.com/products/wolfssl/). 4 August 2017. Retrieved 2019-01-31.

1. **[^](#cite_ref-7)** [OpenSSL: Source, License](https://www.openssl.org/source/license.html)

1. **[^](#cite_ref-8)** [wolfSSL – License](https://www.wolfssl.com/wolfSSL/License.html)

1. **[^](#cite_ref-9)** ["MySQL, Building MySQL with Support for Secure Connections"](https://web.archive.org/web/20170706085054/https://dev.mysql.com/doc/refman/5.7/en/building-with-secure-connection-support.html). Archived from [the original](http://dev.mysql.com/doc/refman/5.7/en/building-with-secure-connection-support.html) on 2017-07-06. Retrieved 2016-06-12.

1. **[^](#cite_ref-10)** [Daniel Stenberg, founder and Chief Architect of cURL, joins wolfSSL](https://www.helpnetsecurity.com/2019/02/07/daniel-stemberg-joins-wolfssl/)

1. **[^](#cite_ref-protocols_11-0)** [wolfSSL – Docs | CyaSSL Manual – Chapter 4 (Features)](https://www.wolfssl.com/wolfSSL/Docs-cyassl-manual-4-features.html)

1. **[^](#cite_ref-12)** ["wolfSSL 3.6.6 is Now Available"](https://www.wolfssl.com/wolfSSL/Blog/Entries/2015/8/24_wolfSSL_3.6.6_is_Now_Available.html).

1. **[^](#cite_ref-13)** [wolfSSL – Docs | wolfSSL Manual – Chapter 10 (wolfCrypt Usage Reference)](https://www.wolfssl.com/wolfSSL/Docs-wolfssl-manual-10-wolfcrypt-usage-reference.html)

1. **[^](#cite_ref-14)** [Kerberos: The Network Authentication Protocol](http://web.mit.edu/kerberos/)

1. **[^](#cite_ref-15)** {{[title=Certificate #2425|url=[https://csrc.nist.gov/projects/cryptographic-module-validation-program/Certificate/2425}}](https://csrc.nist.gov/projects/cryptographic-module-validation-program/Certificate/2425}})

1. **[^](#cite_ref-16)** {{[title=Certificate #3389|url=[https://csrc.nist.gov/Projects/cryptographic-module-validation-program/Certificate/3389}}](https://csrc.nist.gov/Projects/cryptographic-module-validation-program/Certificate/3389}})

1. **[^](#cite_ref-17)** {{[title=Certificate #4718|url=[https://csrc.nist.gov/projects/cryptographic-module-validation-program/certificate/4718}}](https://csrc.nist.gov/projects/cryptographic-module-validation-program/certificate/4718}})

1. **[^](#cite_ref-18)** {{[title=Certificate #5041|url=[https://csrc.nist.gov/projects/cryptographic-module-validation-program/certificate/5041}}](https://csrc.nist.gov/projects/cryptographic-module-validation-program/certificate/5041}})

1. ^ [***a***](#cite_ref-securityinnovation_19-0) [***b***](#cite_ref-securityinnovation_19-1) [NTRU CryptoLabs](http://securityinnovation.com/cryptolab/) [Deprecated link](https://en.wikipedia.org/wiki/Wikipedia:Archive.today_guidance) archived 2013-02-02 at [archive.today](/source/Archive.today)

1. **[^](#cite_ref-20)** [wolfSSL – wolfSSL with Intel® SGX](https://www.wolfssl.com/wolfssl-with-intel-sgx/)

## External links

- [wolfSSL/CyaSSL Homepage](https://www.wolfssl.com)

- [wolfSSL Now With ChaCha20 and Poly1305](http://embedded-computing.com/news/wolfssl-with-chacha20-poly1305)

v t e Cryptographic software Email clients Apple Mail Autocrypt Claws Mail Enigmail GPG Gpg4win GPG Mail Kontact Outlook p≡p PGP Proton Mail Sylpheed Thunderbird Secure communication OTR Adium BitlBee Centericq ChatSecure climm Jitsi Kopete Profanity SSH Dropbear lsh OpenSSH PuTTY SecureCRT WinSCP wolfSSH TLS & SSL BBM Enterprise Bouncy Castle BoringSSL Botan cryptlib GnuTLS JSSE LibreSSL MatrixSSL NSS OpenSSL mbed TLS BSAFE SChannel SSLeay stunnel TeamNote wolfSSL VPN Check Point VPN-1 Hamachi Openswan OpenVPN SoftEther VPN strongSwan Tinc WireGuard ZRTP Jitsi Linphone Jami Zfone P2P Bitmessage Briar RetroShare Tox DRA Matrix OMEMO Cryptocat ChatSecure Proteus Session Signal Protocol Facebook Messenger Google Allo Google Messages Signal TextSecure WhatsApp Zangi Olvid Disk encryption (Comparison) BestCrypt BitLocker Cryptoloop dm-crypt DriveSentry E4M eCryptfs FileVault FreeOTFE GBDE geli LUKS PGPDisk Private Disk Scramdisk Sentry 2020 TrueCrypt History VeraCrypt Anonymity GNUnet I2P Java Anon Proxy Mixnet Tor Vidalia RetroShare Ricochet Wickr File systems (List) EncFS EFS eCryptfs LUKS PEFS Rubberhose StegFS Tahoe-LAFS Security-focused operating system GrapheneOS Tails Qubes Service providers Hyphanet NordLocker Proton Drive Tresorit WinPT Wuala Educational CrypTool Anti–computer forensics USBKill BusKill Related topics Outline of cryptography Timeline of cryptography Hash functions Cryptographic hash function List of hash functions Homomorphic encryption End-to-end encryption S/MIME Category Commons

v t e TLS and SSL Protocols and technologies Transport Layer Security / Secure Sockets Layer (TLS/SSL) Datagram Transport Layer Security (DTLS) Server Name Indication (SNI) Application-Layer Protocol Negotiation (ALPN) DNS-based Authentication of Named Entities (DANE) DNS Certification Authority Authorization (CAA) HTTPS HTTP Strict Transport Security (HSTS) HTTP Public Key Pinning (HPKP) OCSP stapling Opportunistic TLS Perfect forward secrecy Public-key infrastructure Automated Certificate Management Environment (ACME) Certificate authority (CA) CA/Browser Forum Certificate policy Certificate revocation Certificate revocation list (CRL) Online Certificate Status Protocol (OCSP) OCSP stapling Domain-validated certificate (DV) Extended Validation Certificate (EV) Public key certificate Public-key cryptography Public key infrastructure (PKI) Root certificate Self-signed certificate See also Domain Name System Security Extensions (DNSSEC) Internet Protocol Security (IPsec) Secure Shell (SSH) History Export of cryptography from the United States Server-Gated Cryptography Implementations Bouncy Castle BoringSSL Botan BSAFE cryptlib GnuTLS JSSE LibreSSL MatrixSSL mbed TLS NSS OpenSSL Rustls s2n-tls SChannel SSLeay stunnel wolfSSL Notaries Certificate Transparency Convergence HTTPS Everywhere Vulnerabilities Theory Man-in-the-middle attack Padding oracle attack Cipher Bar mitzvah attack Protocol BEAST BREACH CRIME DROWN Logjam POODLE (in regards to SSL 3.0) Implementation Certificate authority compromise Random number generator attacks FREAK goto fail Heartbleed Lucky Thirteen attack POODLE (in regards to TLS 1.0) Kazakhstan MITM attack

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Adapted from the Wikipedia article [WolfSSL](https://en.wikipedia.org/wiki/WolfSSL) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/WolfSSL?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.