ACVP and FIPS 140-3

As many in the FIPS world are aware NIST retired CAVP (Cryptographic Algorithm Validation Protocol) testing on June 30th of 2020, permanently replacing CAVP with ACVP (Automated Cryptographic Validation Protocol), also referred to as ACVTS (Automated Cryptographic Validation Test System).

In order to prepare for this transition NIST offered a “demo server” that Vendors like wolfSSL and FIPS Labs could utilize in standup of the new protocol. Once the transition was completed NIST also setup “production servers” which only FIPS Labs with a trusted certificate issued by NIST can connect to; Production Vectors passing are now the gateway to Algorithm Certification (IE certs like the ones wolfSSL just received!).

Algorithm Certification is a prerequisite to CMVP FIPS 140-2 (and 140-3) validations. This design keeps in place the need for a FIPS lab to achieve algorithm certification but it now allows for Vendors such as wolfSSL to pre-test in advance of requesting production vectors for certification! wolfCrypt has been listed on the CMVP IUT List for FIPS 140-3! We are currently working with our testing lab to get validated as quickly as possible with the new FIPS standard from the NIST. wolfSSL is the first software library on the FIPS 140-3 IUT list for embedded development.

Concurrently wolfSSL is also in the process of developing our own ACVP client based off of the current draft (draft-fussell-acvp-spec-01). Having many algorithms already completing the validation process through the NIST operated ACVP Demo server. Where our test vendor information can be seen publicly listed on the demo site here (

More on ACVP’s

ACVP stands for (Automated Cryptographic Validation Protocol) and it is the upcoming protocol that will be used for FIPS validation. This is going to be a prerequisite certificate for the CMVP(Cryptographic Module Validation Program) and CAVP(Cryptographic Algorithm Validation Program) certificates.

ACVP makes testing cryptographic algorithms and modules more efficient than the current method and more automated. There are three main parts to ACVP – a server, a proxy, and a client.

  • The server side handles requests for test vectors and requests for validation among other requests. This side is operated by a FIPS lab or by NIST themselves.
  • A proxy with ACVP can be used to communicate to offline systems and handle transferring information from the system being tested to the server. Often an ACVP client is used instead.
  • The last part being a client, which is most relevant to users who are wanting to get their cryptography FIPS validated. An ACVP client is directly hooked up to the module to be tested and then communicates with the ACVP server to send requests for test vectors, responses of the results from running those tests, and requests for algorithm validation. There are multiple pieces required to build a ACVP client in order to complete a validation process, some of the large portions of the effort go into
    • JSON parsing / creation for communication with a ACVP server
    • HTTPS GET / POST / PUT / DELETE messages used for securely transporting information
    • 2 factor authentication with TOTP (Time-Based One-Time Password Algorithm)
    • Plugging in the test harness that runs crypto operations

Ultimately an ACVP client communicates with the server to validate cryptographic operations. This includes creating, or referencing meta data such as; vendor, OE, and module information. A simplified message flow for getting an algorithm validated is as follows:

We can assist with your FIPS needs. Contact us at for questions or more information.

More information from NIST’s website about the ACVP project can be found here:

wolfSSL Examples Repository

From the early days of the wolfSSL library, we have provided example clients and servers with wolfSSL. These examples have shown how easy it is to use wolfSSL in various configurations. We also use them to help test the library. Over the years we’ve added new features available with TLS to our examples, and our examples have grown a little complicated.

Enter the wolfSSL Examples GitHub repository. We tasked some of our interns, with little to no experience with the wolfSSL library, to write some example clients and servers that set up and test various types of connections. They give you a bare-bones simple demonstration on how to set up a client or server using wolfSSL. We also have examples showing off how to use some features of the library like the certificate manager. 

The repository contains example applications, written in C, which demonstrate how to use the wolfSSL lightweight SSL/TLS library for secure communication. Each directory represents a unique topic (SSL/TLS, DTLS, PSK, etc.) and contains a Makefile as well as a simple tutorial on the given topic.


Current Examples:

  • utasker (uTasker wolfSSL Example Tasks)

This directory contains example uTasker client and server tasks that demonstrate using wolfSSL with the uTasker stack. These have been tested on the uTasker Simulator.

Please see the utasker/ for further usage and details.

  • android (Android NDK Examples)

This directory contains examples that demonstrate using wolfSSL and wolfSSLJNI on the Android platform, using the Android NDK toolchain.

Please see the android/ for further usage and details.

  • certfields (X509 field extraction)

This directory contains an example that demonstrates using the wolfSSL to read a DER encoded certificate and extract the public key and subject name information.

Please see the certfields/ for further usage and details.

  • certmanager (wolfSSL CertManager)

This directory contains examples that demonstrate using the wolfSSL CertManager (Certificate Manager) functionality.

Please see the certmanager/ for further usage and details.

  • wolfCLU (wolfSSL Command Line Utility)

This is a tool to provide command line access to wolfcrypt cryptographic libraries. wolfSSL command line utility will allow users to encrypt or decrypt a user specified file to any file name and extension.

Please see the clu/ for further usage and details.

Unique feature to wolfSSL CLU

The decision to allow for unique file extensions was prompted by automated tools available for brute forcing files. It will not provide extra security cryptographically however it will force attackers to check the header information on every single brute force attempt. This will provide further frustration and an extra step in any attempt to brute force a file encrypted with our utility.

This directory contains examples of using DTLS, with client and server examples demonstrating UDP, DTLS, non-blocking, session resumption, and multi-threading.

When compiling wolfSSL for use with these examples, wolfSSL will need to be compiled with DTLS support:

cd wolfssl-[version]
./configure --enable-dtls

Examples in this directory may be compiled using:

cd ./dtls

This directory contains examples of using PSK, with client and server examples demonstrating TCP/IP, PSK, non-blocking, session resumption, and multi-threading.

When compiling wolfSSL for use with these examples, wolfSSL will need to be compiled with PSK support:

cd wolfssl-[version]
./configure --enable-psk

Examples in this directory may be compiled using:

cd ./psk

This directory contains examples of using SSL/TLS, with client and server examples demonstrating TCP/IP, SSL/TLS, non-blocking, session resumption, and multi-threading.

Examples in this directory may be compiled using:

cd ./tls

This directory contains examples for securing a Bluetooth Low Energy Link (BTLE). BTLE packets are small and throughput is low, so these examples demonstrate a way to exchange data securely without BTLE pairing.


When necessary, examples will use the example certificates and keys located in the ./certs directory. These certificates and keys have been pulled in from the main wolfSSL repository.


Please contact wolfSSL at with any questions, bug fixes, or suggested feature additions.


Upcoming Webinar: Introducing wolfSentry, an Embeddable IDPS

wolfSSL personally invites you to our wolfSentry webinar, where we are introducing our newest product wolfSentry, a universal, dynamic, embeddable IDPS (intrusion detection and prevention system)! Join us to learn about about what an IDPS is, why you should care, and wolfSentry is the solution to all of your problems

About the webinar:

When: Mar 31, 2021 10:00 AM Pacific Time (US and Canada)
Topic: Introducing wolfSentry, an Embeddable IDPS

Register in advance for this webinar:

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

Please bring any questions you have, and we look forward to seeing you there!

wolfTPM brings TPM Physical Presence and IO Support to Embedded Systems

We see a continuing adoption of wolfTPM and TPM 2.0 modules in IoT and Edge embedded systems. In addition, there is a new trend of adding wolfTPM to safety-critical systems, such as aerospace and medical products. For many years, there was no TPM 2.0 stack designed for baremetal and RTOS systems and wolfTPM changed this.

Today, we can announce that wolfTPM is also the first TPM 2.0 stack to support Physical Presence (PP). This feature allows the user to confirm TPM 2.0 operations by asserting physical input to the TPM chip and increase the level of security assurance for critical operations.

For example, TPM2_Clear is a command that returns the TPM to a factory state, destroying existing primary and storage keys, and can be safeguarded by a PP request. TPM2_Clear is typically used when onboarding a new owner of a system, e.g. second market or internal change of ownership equipment.

PP requests are satisfied by controlling a dedicated I/O pin on the TPM chip and now wolfTPM has the capability to extend the list of commands that require it. This could be used to restrict certain operations. It could also be used in existing designs to replace a mechanical switch previously used for Physical Presence.

Another new feature of wolfTPM is the ability to control extra I/O pins available on TPM modules, such as the STMicroelectronics ST33 TPM 2.0 module. The developer can use a single wolfTPM call to control additional I/O pins and pass physical signals, as sign of security or system events, to other subsystems.


For more information about TPM 2.0 Physical Presence and extra I/O support, please contact us at 

wolfSSL Online Certificate Status Protocol (OCSP) Support

wolfSSL supports the Online Certificate Status Protocol (OCSP) [] as a client and OCSP stapling version 1 [] and 2 []. OCSP is a substitute for Certificate Revocation Lists (CRL). CRLs are a list of certificates that shouldn’t be temporarily or permanently trusted. A major setback for CRLs is the time it takes for these lists to propagate. It may take up to a week [] due to CRLs being issued periodically by Certificate Authorities (CA). OCSP allows clients to verify the validity of server certificates with an OCSP responder and know in real time whether to trust a certificate or not.

OCSP stapling is a TLS extension sent by a client that instructs the server that it would like to receive certificate status information. Stapling significantly cuts down on bandwidth and on round trips needed to set up a connection. When a TLS server receives the Certificate Status Request extension from a client, it will transmit the OCSP responders complete, DER-encoded OCSP response. This relieves the client from having to ask an OCSP responder about the certificate validity and saves the OCSP responder bandwidth coming from clients of a frequently visited server.

OCSP stapling version 1 is severely limited by being able to only transmit the status information of only one certificate. Many TLS servers opt to send intermediate certificates along with its own certificate in case clients do not know the intermediate certificate chain. OCSP stapling version 1 will only save the client the trouble of confirming the status of the server’s certificate, but not of checking the intermediate certificates. OCSP stapling version 2 defines a new extension that allows “servers […] to provide status information about not only the server’s own certificate but also the status of intermediate certificates in the chain” [].

To compile wolfSSL with OCSP support, use the following configure options:
OCSP: --enable-ocsp
OCSP stapling: --enable-ocspstapling
OCSP stapling v2: --enable-ocspstapling2

The following API are available in wolfSSL to enable OCSP usage:

int wolfSSL_CTX_EnableOCSP(WOLFSSL_CTX*, int options);
 int wolfSSL_CTX_DisableOCSP(WOLFSSL_CTX*);
 int wolfSSL_CTX_SetOCSP_OverrideURL(WOLFSSL_CTX*, const char*);
 CbOCSPIO, CbOCSPRespFree, void*);
 int wolfSSL_CTX_EnableOCSPStapling(WOLFSSL_CTX*);
 int wolfSSL_CTX_DisableOCSPStapling(WOLFSSL_CTX*);
 int wolfSSL_CTX_EnableOCSPMustStaple(WOLFSSL_CTX*);
 int wolfSSL_CTX_DisableOCSPMustStaple(WOLFSSL_CTX*);

The following flow is enough to use OCSP in wolfSSL:

wolfSSL_CTX_EnableOCSP(ctx, 0);

To use OCSP stapling:

 wolfSSL_UseOCSPStapling(ssl, WOLFSSL_CSR_OCSP, 0);
 wolfSSL_CTX_EnableOCSP(ctx, 0);

To use OCSP stapling version 2:

 wolfSSL_UseOCSPStaplingV2(ssl, WOLFSSL_CSR2_OCSP*, 0);
 wolfSSL_CTX_EnableOCSP(ctx, 0);

* To provide status request information for intermediate certificates use WOLFSSL_CSR2_OCSP_MULTI

To allow the server to provide OCSP stapling responses use:

wolfSSL_CTX_EnableOCSP(ctx, 0);

To provide a custom OCSP responder URL use:

wolfSSL_CTX_SetOCSP_OverrideURL(ctx, ocspUrl);

OCSP stapling version 2 can’t be used with TLS 1.3 as it has been deprecated []. TLS 1.3 uses OCSP stapling version 1 but the certificate status is not a separate message. Instead it is included as an extension to the corresponding certificate.

To learn more about the many features of wolfSSL, email us at

wolfSSL OpenVPN Upstream Support

Support for wolfSSL has been upstreamed to the master OpenVPN branch in f6dca235ae560597a0763f0c98fcc9130b80ccf4! This means that you will be able to use wolfSSL directly in OpenVPN. wolfSSL is a lightweight and embedded SSL/TLS library that is extensively tested to provide the best security available. Using OpenVPN with wolfSSL, you can take advantage of our hardware cryptography and acceleration on many platforms.

To use OpenVPN with wolfSSL:

Compile wolfSSL with:

./configure --enable-openvpn
make install

Compile OpenVPN with:

./configure --with-crypto-library=wolfssl
make check
make install

Contact us at with any questions or feedback.

FIPS certificate #2425 is being added to NIST sunset list: wolfSSL customers can achieve effortless transition to FIPS cert #3389

FIPS 140-2 requires the use of validated cryptography in the security systems implemented by federal agencies to protect sensitive information. The wolfCrypt Module is a comprehensive suite of FIPS Approved algorithms. All key sizes and modes have been implemented to allow flexibility and efficiency.

The National Institute of Standards and Technology (NIST) is sending FIPS cert #2425 into sunset June 2021. For customers who will be impacted, the wolfCrypt Cryptographic Module maintains its #3389 certificate and can be used in conjunction with the wolfSSL embedded SSL/TLS library for full TLS 1.3 client and server support. Upgrade your FIPS cert with wolfSSL to stay afloat and benefit from: 

  • Algorithm support for TLS 1.3!
  • New algorithms such as AES (CBC, GCM, CTR, ECB), CVL, Hash DRBG, DSA, DHE, ECDSA (key generation, sign, verify), HMAC, RSA (key generation, sign, verify), SHA-3, SHA-2, SHA-1, and Triple-DES
  • Hardware encryption support for NXP’s Cryptographic Assistance and Assurance Module (CAAM), NXP Memory-Mapped Cryptographic Acceleration Unit (mmCAU), Intel’s AES-NI, and more
  • Support for secure elements and TPM’s
  • Interoperability with wolfBoot, wolfSSH, and wolfTPM
  • Integration support for third party libraries such as strongswan, nginx, python and more

Contact us to upgrade to FIPS cert #3389 at

Additional Resources 

Learn more about wolfSSL support for FIPS cert #3389: 

For a list of supported Operating Environments for wolfCrypt FIPS, check our FIPS page: 

Our FIPS Story

wolfSSL is currently the leader in embedded FIPS certificates. We have a long history in FIPS starting with wolfCrypt FIPS 140-2 Level 1 Certificate #2425 as well as wolfCrypt v4 FIPS 140-2 Level 1 Certificate #3389. wolfSSL partners with FIPS experts KeyPair to bring you FIPS consulting services, and high assurance along each step of your FIPS certification process. Additionally, wolfSSL will be the first implementation of FIPS 140-3.

wolfSSL also provides support for a wolfCrypt FIPS Ready version of the library! wolfCrypt FIPS Ready is our FIPS enabled cryptography layer code included in the wolfSSL source tree that you can enable and build. You do not get a FIPS certificate, you are not FIPS approved, but you will be FIPS Ready. FIPS Ready means that you have included the FIPS code into your build and that you are operating according to the FIPS enforced best practices of default entry point, and power on self test.

wolfCrypt FIPS Ready can be downloaded from the wolfSSL download page located here: More information on getting set up with wolfCrypt FIPS Ready can be found in our FIPS Ready User guide here:


wolfSSL Cisco cjose Port

The wolfSSL library has added support for the cisco/cjose library in version 4.4.0. cjose implements Javascript Object Signing and Encryption (JOSE) in C/C++. JOSE is a framework that allows parties to exchange transfer claims in a secure way. The cjose library has been ported to work with wolfSSL, the best tested crypto library on the market.

To build wolfSSL for cjose:

  • ./configure --enable-opensslall --enable-aeskeywrap CPPFLAGS='-DHAVE_EX_DATA -DWOLFSSL_KEY_GEN'
  • make
  • make install

To build cjose for wolfSSL:

  • Download the appropriate patch from Choose a patch that corresponds or is closest to your version of cjose.
  • patch -p1 < <path/to/downloaded/patch>
  • autoreconf
  • ./configure --with-wolfssl=/usr/local
  • make

To verify that this build passes the tests run:

  • make check

wolfSSL currently supports cjose version 0.6.1,

Feel free to contact us at for additional information and help with using the new features of wolfSSL.

This feature has been added in commit 0cfde0794b9c5ab1c01171745b800140ee4f8662.

wolfSSL 4.7.0 has added support for S/MIME!

S/MIME is short for Secure/Multipurpose Internet Mail Extensions, a standard for public key encryption and signing of MIME data. The S/MIME standard allows you to sign, authenticate and encrypt plaintext MIME messages. It is commonly used in email. wolfSSL now supports both “enveloped data” (application/pkcs7-mime) and “detached signature” (multipart/signed) messages.

To enable S/MIME support in wolfSSL, run ./configure with the --enable-smime flag, or add HAVE_SMIME to your user_settings.h file. Then, call wolfSSL_SMIME_read_PKCS7() with 2 parameters:

  1. A BIO object containing your S/MIME message.
  2. A NULL BIO pointer which will be set to the signed data in case of a multipart message.
  3. This function call will give you a PKCS7 pointer, or NULL in case of an error.

If you have any questions, don’t hesitate to contact us at

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