Oberon HomeKit Accessory Protocol (OberonHAP) #
Between January and April 2015, I co-developed an implementation of Apple’s HomeKit Accessory Protocol (HAP) at Oberon microsystems AG. Our initial target was Bluetooth Low Energy (BLE) chipsets, specifically the Nordic Semiconductor nRF51 featuring an ARM Cortex-M0 core, 32kB of RAM, and 256kB of ROM.
Initial pairing on this constrained platform took just under 30 seconds—within the early HomeKit and BLE specification requirements. While pairing was sluggish due to the resource-intensive Secure Remote Password (SRP) protocol—which involved a 384-bit integer multiplication—subsequent reconnections were fast and seamless thanks to modern cryptographic algorithms like Ed25519 and ChaCha20-Poly1305. These significantly helped the user experience by making the accessory feel responsive and reliable.
The result was a compact, efficient implementation named OberonHAP, available under license. Shortly afterward, I transitioned to a different project with ETH/MeteoSwiss.
Rejoining the Project #
In early 2018, I rejoined the OberonHAP effort, supporting customers as they integrated the enhanced version of the library—now featuring IP transport—into their products. I provided example implementations for various HomeKit profiles and assisted in tailoring integrations to their specific needs. At the end of the project, we shipped binary releases for more than 50 platform variants, using a wide array of compilers including Clang, GCC, IAR, Keil, Microsoft Visual Studio (2008 and 2019), and Xtensa. Due to the increased memory and performance requirements introduced by IP support, we phased out support for Cortex-M0 targets.
Oberon microsystems AG is now listed as a contributor to the Apple HomeKit ADK on GitHub:
The cryptographic engine behind OberonHAP lives on in a standalone library: OCrypto.
I left Oberon microsystems at the end of 2019 to join Meteomatics.