Crypto: RSA

The RSA sample shows how to perform singing and verification of a sample plaintext using a 1024-bit key.


The sample supports the following development kits:

Hardware platforms


Board name

Build target

nRF9160 DK



nrf9160dk_nrf9160_ns nrf9160dk_nrf9160

nRF5340 DK



nrf5340dk_nrf5340_cpuapp_ns nrf5340dk_nrf5340_cpuapp

nRF52840 DK




When built for an _ns build target, the sample is configured to compile and run as a non-secure application with Cortex-M Security Extensions enabled. Therefore, it automatically includes Trusted Firmware-M that prepares the required peripherals and secure services to be available for the application.


The sample performs the following operations:

  1. Initialization:

    1. The Platform Security Architecture (PSA) API is initialized.

    2. A random RSA key pair is generated and imported into the PSA crypto keystore.

    3. The public key of the RSA key pair is imported into the PSA crypto keystore.

  2. RSA signing and verification:

    1. Signing is performed using the RSA private key.

    2. The signature is verified using the exported public key.

  3. Cleanup:

    1. The RSA key pair and public key are removed from the PSA crypto keystore.

Building and running

This sample can be found under samples/crypto/rsa in the nRF Connect SDK folder structure.

When built as firmware image for the _ns build target, the sample has Cortex-M Security Extensions (CMSE) enabled and separates the firmware between Non-Secure Processing Environment (NSPE) and Secure Processing Environment (SPE). Because of this, it automatically includes the Trusted Firmware-M (TF-M). To read more about CMSE, see Processing environments.

To build the sample with Visual Studio Code, follow the steps listed on the How to build an application page in the nRF Connect for VS Code extension documentation. See Building and programming an application for other building and programming scenarios and Testing and debugging an application for general information about testing and debugging in the nRF Connect SDK.


After programming the sample to your development kit, complete the following steps to test it:

  1. Connect to the kit with a terminal emulator (for example, PuTTY). See How to connect with PuTTY for the required settings.

  2. Compile and program the application.

  3. Observe the logs from the application using an RTT Viewer or a terminal emulator.


By default, the sample is configured to use both RTT and UART for logging. If you are using RTT, skip the first step of the testing procedure.