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In addition, wolfSSL now has a support-specific blog page dedicated to answering some of the more commonly received support questions.

Upcoming Webinar: Secure and Reliable Firmware Updates with wolfBoot

Please join us for our upcoming webinar with Sr. Engineer and Security Expert Daniele Lacamera!

Connected embedded systems that support remote updates of different artifacts must take into account the security risks involved. A secure boot mechanism is the best way to prevent the execution of unauthorized code. Our universal, open-source, secure bootloader, wolfBoot, takes care of authenticating and installing new valid firmware images. Due to its transport-agnostic update management, it can be combined with any secure transfer implementation to provide secure and reliable firmware updates.

In this short webinar, we explore some of the possibilities of real-life secure firmware update solutions, designed using the latest standards and best cryptography algorithms.

When: Mar 17, 2021 09:00 AM Pacific Time (US and Canada)
Topic: Webinar: Secure and reliable Firmware updates with wolfBoot

Register in advance for this webinar:

After registering, you will receive a confirmation email containing information about joining the webinar.

Bring any questions you may have, and we look forward to seeing you there!

wolfSSL Xilinx Support

wolfSSL  supports Xilinx SoCs and FPGAs. The wolfSSL embedded SSL/TLS library can be used with FPGAs which use the MicroBlaze CPU and/or Zynq and Zynq UltraScale+ SoCs. Improved performance speeds with using the hardware crpyto can be seen. Increasing AES-GCM, RSA, and SHA3 operations performance. In addition to the performance gained a user also gets the additional security the hardware provides while executing the algorithms.

For more information contact 

Building Qt with wolfSSL Support

Did you know that you can build Qt 5.12 and 5.13 against the wolfSSL embedded SSL/TLS library instead of the default OpenSSL backend?  Using wolfSSL as a TLS provider in Qt can have many advantages, depending on application and industry.  Some of these may include:

To compile wolfSSL for Qt, wolfSSL includes a configure option named --enable-qt.  To compile Qt with the wolfSSL, first obtain the Qt patch file from wolfSSL (contact us at, then follow the steps below:

1. Follow the Building Qt Guide to download needed Qt dependencies and initialize the Qt repository.
2. Change directories into the qt5 directory and checkout a branch between 5.12-5.13.

$ cd qt5
$ git checkout [branch_name]

3. Apply the wolfSSL Qt patch file to qt5.

$ cd qt5/qtbase
$ patch -p1 < /path/to/wolfssl_qt_src.patch

4. Link to wolfSSL directly by setting the WOLFSSL_LIBS variable.

$ export WOLFSSL_LIBS="-L/path/to/wolf-install/lib -lwolfssl"

5. Configure Qt using the “-wolfssl-linked” option, and add wolfSSL header directories to the include path.

$ ./configure -wolfssl-linked -I/path/to/wolf-install/include/wolfssl -I/path/to/wolf-install/include

6. Build Qt.

$ make

7. Test the build.

$ make test

8. Or, run tests individually:

$ qtbase/tests/auto/network/ssl/qsslcertificate/tst_qsslcertificate
$ qtbase/tests/auto/network/ssl/qasn1element/tst_qasn1element
$ qtbase/tests/auto/network/ssl/qpassworddigestor/tst_qpassworddigestor 
$ qtbase/tests/auto/network/ssl/qsslcipher/tst_qsslcipher
$ qtbase/tests/auto/network/ssl/qssldiffiehellmanparameters/tst_qssldiffiehellmanparameters
$ qtbase/tests/auto/network/ssl/qsslellipticcurve/tst_qsslellipticcurve 
$ qtbase/tests/auto/network/ssl/qsslerror/tst_qsslerror 
$ qtbase/tests/auto/network/ssl/qsslkey/tst_qsslkey 
$ qtbase/tests/auto/network/ssl/qsslsocket/tst_qsslsocket
$ qtbase/tests/auto/network/ssl/qsslsocket_onDemandCertificates_member/tst_qsslsocket_onDemandCertificates_member
$ qtbase/tests/auto/network/ssl/qsslsocket_onDemandCertificates_static/tst_qsslsocket_onDemandCertificates_static

wolfSSL’s port into Qt has not been merged upstream yet, and is currently distributed in patch form.  To request access to the wolfSSL Qt patch file, please email us at!

Do you need to secure your ARINC 653?

Did you know that wolfSSL is OS and architecture agnostic, and it can run on bare metal? Did you know that we have DO-178C artifacts for our wolfCrypt software?

The DO-178C wolfCrypt product which is a cryptographic foundation for secure boot and secure firmware update has been integrated and tested with various operating systems including multi-core ARINC 653 compliant Wind River VxWorks 653 and DDC-I’s DO-178C Level A Deos real-time operating system.

You can start using wolfCrypt as an application with ARINC 653 for space and time partitioning in safety-critical avionics real-time operating systems (RTOS).

Let us know if you need help with security for your ARINC 653 requirements. We can make a world of difference for you!

For more information about wolfSSL, or help getting started with using it in your project, contact us at

wolfSSL DTLS Bandwidth Optimization

wolfSSL provides a robust and secure DTLS 1.2 implementation. During the handshake process, wolfSSL will re-send its previous flight of messages in the following circumstances:

  1. a network timeout has occurred waiting on data to arrive for processing
  2. the last message of the peer’s current flight has been received out of order
  3. a duplicate of the first message of the peer’s current flight has been received

These steps aim to provide a fast and reliable connection process. Unfortunately, the latter two cases may cause wolfSSL to use up more bandwidth than would be necessary for the handshake. If network bandwidth is at a premium for you and you are less worried about latency, then wolfSSL 4.7.0 has introduced a new macro: WOLFSSL_DTLS_RESEND_ONLY_TIMEOUT.

Compile wolfSSL with this macro, either by adding it to your configure command (for example ./configure --enable-dtls CPPFLAGS=-DWOLFSSL_DTLS_RESEND_ONLY_TIMEOUT) or by defining it in your user_setting.h header file. This macro instructs wolfSSL to only re-send its last flight of messages on a network timeout. In practice, wolfSSL will wait longer before re-sending handshake messages so that re-ordered messages get a chance to be processed and duplicate messages don’t trigger re-sends.

If you are interested in using the new features available in wolfSSL 4.7.0, please contact us at

Introducing wolfSentry – An Embedded IDPS

wolfSSL has a major new product in development — wolfSentry, the universal, dynamic, embedded IDPS (intrusion detection and prevention system). At a high level, wolfSentry is a dynamically configurable logic hub, arbitrarily associating user-defined events with user-defined actions, contextualized by connection attributes, tracking the evolution of the client-server relationship. At a low level, wolfSentry is an embedded firewall engine (both static and fully dynamic), with O(log n) lookup of known hosts/netblocks.

wolfSentry will be fully integrated into the wolfSSL library, wolfMQTT, and wolfSSH, with optional in-tree call-ins and callbacks that give application developers turnkey IDPS across all network-facing wolfSSL products, with a viable zero-configuration option. These integrations will be available via simple --enable-wolfidps configure options in wolfSSL sibling products.

The wolfSentry engine will be dynamically configurable programmatically through an API, or from a textual input file supplied to the engine. Callback and client-server implementations will also be supplied that deliver advanced capabilities including remote logging through MQTT or syslog, and remote configuration and status queries, all cryptographically secured.

Notably, wolfSentry is designed from the ground up to function well in resource-constrained, bare-metal, and realtime environments, with algorithms to stay within designated maximum memory footprints and maintain deterministic throughput. Opportunities include RTOS IDPS, and IDPS for ARM silicon and other common embedded CPUs and MCUs. wolfSentry with dynamic firewalling can add as little as 64k to the code footprint, and 32k to the volatile state footprint, and can fully leverage the existing logic and state of applications and sibling libraries.

The first beta release of wolfSentry is planned for April 2021, with turnkey product integrations to follow.

For questions or help getting started using wolfSSL in your project, contact us at! wolfSSL supports TLS 1.3, FIPS 140-2/140-3, DO-178C, and more!

RFC 5705: Keying Material Exporters for TLS

With the release of wolfSSL 4.7.0, we now support Keying Material Exporters for TLS as defined in RFC 5705! This new functionality allows applications to establish common secrets using the underlying (D)TLS connection. A popular project that makes use of exported keying material is OpenVPN (which wolfSSL supports!). It uses the user provided label, in the --keying-material-exporter option, to generate secure shared secrets for use by plugins from the (D)TLS connection.

To export keying material in wolfSSL, use the new API:

int wolfSSL_export_keying_material(WOLFSSL *ssl,
    	unsigned char *out, size_t outLen,
    	const char *label, size_t labelLen,
    	const unsigned char *context, size_t contextLen,
    	int use_context);

This API outputs outLen data to out. The label and context match those defined in the RFC:

label – “a disambiguating label string”
context – “a per-association context value provided by the [wolfSSL user]”

If you are interested in using the new features available in wolfSSL 4.7.0, please contact us at

wolfSSL, Session Tickets, TLS 1.3 and TLS 1.2

At wolfSSL we have found more and more customers choosing to use TLS 1.3. That’s great! More businesses are taking advantage of the improved security in the new protocol. These customers are finding that they need to use session tickets for resumption for the first time in their applications. In the latest release of wolfSSL, 4.7.0, we’ve made this easier than ever.

Encryption Algorithm

Session tickets require the implementation of a callback that encrypts and decrypts them on the server. There is a great example of how in wolfssl/test.h. Take a look at myTicketEncCb(). Previously the callback encrypted with ChaCha20-Poly1305 but now we include using AES-GCM instead. Choose the one that suites your application!

Default Encryption Callback

At wolfSSL we decided that a default callback was a valuable addition. wolfSSL 4.7.0 now includes a default session ticket encryption callback. Understanding how it works will inform you as to whether to use the default or write your own.

The callback is encrypting and decrypting the session ticket. You can choose which encryption algorithm to use by defining one of the following:

  • WOLFSSL_TICKET_ENC_CHACHA20_POLY1305 – use ChaCha20-Poly1305
  • WOLFSSL_TICKET_ENC_AES128_GCM – use AES-GCM with 128-bit key
  • WOLFSSL_TICKET_ENC_AES256_GCM – use AES-GCM with 256-bit key

Otherwise, the default will be ChaCha20-Poly1305. If that algorithm is not compiled in then it will use AES-GCM with a 128-bit key.

There are two keys that are generated in the callback: primary and secondary. The primary key is generated, with a private random number generator, at first use and which point it is given a lifetime. By default, this is one hour. It can be customized at the second resolution by defining WOLFSSL_TICKET_KEY_LIFETIME. The lifetime must be larger than the lifetime of a session ticket which is 5 minutes by default. This too can be changed at the second resolution by defining SESSION_TICKET_HINT_DEFAULT. The longer the key lifetime the longer the exposure time if a key is compromised.

There are two lifetimes for a key: encryption and decryption. A key used to encrypt a ticket must be kept for the life of the ticket. Therefore the encryption lifetime is shorter than the total key lifetime, or decryption lifetime, by the ticket lifetime. See the diagram below:

If the primary key is expired for encryption but not for decryption, i.e is in the shaded area above, then a secondary key is generated on the next encrypt request. See below.

The secondary key is used until it expires for encryption and only then will a new primary key be generated. Note that in the scenario where session tickets are not commonly used, the primary key may expire for decryption before a new call for encryption. In this case, a new primary key will be generated. In a threaded environment, the generation of the global keys are protected by a mutex to ensure no overwriting.

Exporting and importing keys is also possible using: wolfSSL_CTX_get_tlsext_ticket_keys() and wolfSSL_CTX_set_tlsext_ticket_keys(). These APIs are useful for sharing keys across processes or server machines and expiration times are included in the blob.

The default session ticket encryption callback will cover most use cases. If you want to use another encryption algorithm, have very limited memory, or need an advanced sharing strategy between servers then define WOLFSSL_NO_DEF_TICKET_ENC_CB and set your own callback.

TLS 1.3 and TLS 1.2 Session Ticket Use

Finally, customers that haven’t been using session tickets for TLS 1.2 connections and now are for TLS 1.3, wanted to prevent session tickets being used with TLS 1.2. A reasonable request that we now support with the functions:


Calling these functions sets a flag against the context or object that results in the handshake ignoring session tickets on the client and server when the protocol version negotiated is TLS 1.2 or lower.

Session tickets are a integral part of TLS 1.3 for resumption. If you have questions about this feature, or have any commentary or feedback please reach out to our team at or!

Upcoming Webinar: DO-178

Do you need to secure your ARINC 664 transmissions?

Did you know that wolfSSL is transport agnostic, and can run on bare metal? Did you know that we have DO-178 artifacts for our software? Are you aware of MITM attacks or spoofing attacks that could compromise your network?

Let us know if you need help with security for your ARINC 664 transmissions. We can make a world of difference for you!

For more information about wolfSSL, or help getting started with using it in your project, contact us at

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