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*** Description ***

The wolfSSL embedded SSL library (formerly CyaSSL) 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. Two versions of the wolfCrypt cryptography library have been FIPS 140-2 validated (Certificate #2425 and certificate #3389). For additional information, visit the wolfCrypt FIPS FAQ ( or contact

*** Why choose wolfSSL? ***

There are many reasons to choose wolfSSL as your embedded SSL solution. Some of the top reasons include size (typical footprint sizes range from 20-100 kB), support for the newest standards (SSL 3.0, TLS 1.0, TLS 1.1, TLS 1.2, TLS 1.3, DTLS 1.0, and DTLS 1.2), current and progressive cipher support (including stream ciphers), multi-platform, royalty free, and an OpenSSL compatibility API to ease porting into existing applications which have previously used the OpenSSL package. For a complete feature list, see chapter 4 of the wolfSSL manual. (

*** Notes, Please read ***

Note 1) wolfSSL as of 3.6.6 no longer enables SSLv3 by default. wolfSSL also no longer supports static key cipher suites with PSK, RSA, or ECDH. This means if you plan to use TLS cipher suites you must enable DH (DH is on by default), or enable ECC (ECC is on by default), or you must enable static key cipher suites with


though static key cipher suites are deprecated and will be removed from future versions of TLS. They also lower your security by removing PFS. Since current NTRU suites available do not use ephemeral keys, WOLFSSL_STATIC_RSA needs to be used in order to build with NTRU suites.

When compiling ssl.c, wolfSSL will now issue a compiler error if no cipher suites are available. You can remove this error by defining WOLFSSL_ALLOW_NO_SUITES in the event that you desire that, i.e., you're not using TLS cipher suites.

Note 2) wolfSSL takes a different approach to certificate verification than OpenSSL does. The default policy for the client is to verify the server, this means that if you don't load CAs to verify the server you'll get a connect error, no signer error to confirm failure (-188).

If you want to mimic OpenSSL behavior of having SSL_connect succeed even if verifying the server fails and reducing security you can do this by calling:

wolfSSL_CTX_set_verify(ctx, SSL_VERIFY_NONE, 0);

before calling wolfSSL_new();. Though it's not recommended.

Note 3) The enum values SHA, SHA256, SHA384, SHA512 are no longer available when wolfSSL is built with --enable-opensslextra (OPENSSL_EXTRA) or with the macro NO_OLD_SHA_NAMES. These names get mapped to the OpenSSL API for a single call hash function. Instead the name WC_SHA, WC_SHA256, WC_SHA384 and WC_SHA512 should be used for the enum name.

*** end Notes ***

wolfSSL Release 4.4.0 (04/22/2020)

If you have questions about this release, feel free to contact us on our info@ address.

Release 4.4.0 of wolfSSL embedded TLS has bug fixes and new features including:

New Feature Additions

  • Hexagon support.
  • DSP builds to offload ECC verify operations.
  • Certificate Manager callback support.
  • New APIs for running updates to ChaCha20/Poly1305 AEAD.
  • Support for use with Apache.
  • Add support for IBM s390x.
  • PKCS8 support for ED25519.
  • OpenVPN support.
  • Add P384 curve support to SP.
  • Add BIO and EVP API.
  • Add AES-OFB mode.
  • Add AES-CFB mode.
  • Add Curve448, X448, and Ed448.
  • Add Renesas Synergy S7G2 build and hardware acceleration.


  • Fix for RSA public encrypt / private sign with RSA key sizes over 2048-bit.
  • Correct misspellings.
  • Secure renegotiation fix.
  • Fix memory leak when using ATECC and non-SECP256R1 curves for sign, verify, or shared secret.
  • Fix the RSA verify only build.
  • Fix in SP C implementation for small stack.
  • Fix using the auth key id extension is set, hash might not be present.
  • Fix when flattening certificate structure to include the subject alt names.
  • Fixes for building with ECC sign/verify only.
  • Fix for ECC and no cache resistance.
  • Fix memory leak in DSA.
  • Fix build on minGW.
  • Fix PemToDer() call in ProcessBuffer() to set more than ECC.
  • Fix for using RSA without SHA-512.
  • Add some close tags to the echoserver HTTP example output.
  • Miscellaneous fixes and updates for static analysis reports.
  • Fixes for time structure support.
  • Fixes for VxWorks support.
  • Fixes for Async crypto support.
  • Fix cache resist compile to work with SP C code.
  • Fixes for Curve25519 x64 asm.
  • Fix for SP x64 div.
  • Fix for DTLS edge case where CCS and Finished come out of order and the retransmit pool gets flushed.
  • Fix for infinite loop in SHA-1 with small inputs. Thanks to Peter W.
  • Fix for FIPS Hmac where wc_HmacInit() isn't used. wc_HmacSetKey() needs to initialize the Hmac structure. Type is set to NONE, and checked against NONE, not 0.
  • Fixes for SP RSA private operations.
  • Fixes for Xilinx SDK and Zynq UltraScale+ MPSoC
  • Fix leak when building with HAVE_AESGCM and NO_AES_DECRYPT. Thanks G.G.
  • Fixes for building ECC without ASN.
  • Fix for async TLSv1.3 issues.
  • Fix wc_KeyPemToDer() with PKCS1 and empty key.
  • Omit -fomit-frame-pointer from CFLAGS in


  • Qt 5.12 and 5.13 support.
  • Added more digest types to Cryptocell RSA sign/verify.
  • Some memory usage improvements.
  • Speed improvements for mp_rand.
  • Improvements to CRL and OCSP support.
  • Refactor Poly1305 AEAD/MAC to reduce duplicate code.
  • Add blinding to RSA key gen.
  • Improvements to blinding.
  • Improvement and expansion of OpenSSL Compatibility Layer.
  • Improvements to ChaCha20.
  • Improvements to X.509 processing.
  • Improvements to ECC support.
  • Improvement in detecting 64-bit support.
  • Refactor to combine duplicate ECC parameter parsing code.
  • Improve keyFormat to be set by algId and let later key parsing produce fail.
  • Add test cases for 3072-bit and 4096-bit RSA keys.
  • Improve signature wrapper and DH test cases.
  • Improvements to the script.
  • Added constant time RSA q modinv p.
  • Improve performance of SP Intel 64-bit asm.
  • Added a few more functions to the ABI list.
  • Improve TLS bidirectional shutdown behavior.
  • OpenSSH 8.1 support.
  • Improve performance of RSA/DH operations on x64.
  • Add support for PKCS7/CMS Enveloped data with fragmented encrypted content.
  • Example linker description for FIPS builds to enforce object ordering.
  • C# wrapper improvements. Added TLS client example and TLSv1.3 methods.
  • Allow setting MTU in DTLS.
  • Improve PKCS12 create for outputting encrypted bundles.
  • Constant time EC map to affine for private operations.
  • Improve performance of RSA public key ops with TFM.
  • Smaller table version of AES encrypt/decrypt.
  • Support IAR with position independent code (ROPI).
  • Improve speed of AArch64 assembly.
  • Support AES-CTR on esp32.
  • Add a no malloc option for small SP math.

This release of wolfSSL includes fixes for 2 security vulnerabilities.

  • For fast math, use a constant time modular inverse when mapping to affine when operation involves a private key - keygen, calc shared secret, sign. Thank you to Alejandro Cabrera Aldaya, Cesar Pereida García and Billy Bob Brumley from the Network and Information Security Group (NISEC) at Tampere University for the report.

  • Change constant time and cache resistant ECC mulmod. Ensure points being operated on change to make constant time. Thank you to Pietro Borrello at Sapienza University of Rome.

For additional vulnerability information visit the vulnerability page at

See INSTALL file for build instructions. More info can be found on-line at

*** Resources ***

wolfSSL Website

wolfSSL Wiki


wolfSSL Documents

wolfSSL Manual

[wolfSSL API Reference] (

[wolfCrypt API Reference] (

TLS 1.3

[wolfSSL Vulnerabilities] (

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