Ascon-128 and Utility Functions for Arduino

This library implements Ascon-128¹ (taken from Rhys Weatherley's great Crypto and CryptoLW libraries), hexadecimal en-/decoding, and Z85 encoding utility functions.

Entry points:

• For memory-constrained systems, as128z85.hpp provides as128_encrypt_print_z85, which encrypts a buffer and immediately prints it to an output stream such as Serial using the Z85 encoding, so that the encrypted buffer doesn't have to be kept in RAM.
• as128.hpp provides simple wrappers for the Ascon128 class that encrypt a buffer and use the 16-byte IV as the unencrypted-but-checksummed "associated data".
• hex.hpp provides several functions to en- and decode hexadecimal strings in-place (or printed directly to an output stream).
• uint128.hpp provides a simple 128-bit integer that can be used as a nonce/IV (monotonically increasing counter).
• And of course you are welcome to use only the Z85 or Ascon128 functions individually.

The code in this repository was tested via run_tests.py on the following:

• Arduino UNO R3 (arduino:avr:uno, i.e. ATmega328P)
• Arduino UNO R4 WiFi (arduino:renesas_uno:unor4wifi)
• Arduino MKR Zero (arduino:samd:mkrzero)
• D1 mini (ESP8266, esp8266:esp8266:d1_mini / esp8266:esp8266:d1_mini_clone)

¹ Specifically, implements Ascon v1.2 Ascon-128 as submitted to NIST LWC and CAESAR, not the final NIST SP 800-232 "Ascon-AEAD128" variant. This implementation is tested against the default variant="Ascon-128" from the Python package ascon 0.0.9.

References:

• https://ascon.isec.tugraz.at/
• https://github.com/meichlseder/pyascon
• https://rweather.github.io/arduinolibs/classAscon128.html
• https://github.com/rweather/arduinolibs/tree/master/libraries/CryptoLW

The reason I split Ascon128 out of Rhys Weatherley's CryptoLW and Crypto libraries and copied it here is that the former currently isn't listed as part of the Arduino library collection, making installation a little trickier, and the latter includes quite a few code files that are not necessary for Ascon128, some of which cause compilation warnings. Plus, its RNG class sets up a WDT ISR vector, which interferes with a custom WDT ISR when RNG is not needed.

Author, Copyright, and License

As mentioned in the header of each source file, parts of this software were derived from: https://github.com/rweather/arduinolibs/tree/37a76b8f7516568e1c575b6dc9268da1ccaac6b6

Copyright (C) 2015, 2018 Southern Storm Software, Pty Ltd.

While other parts are:

Copyright (c) 2026 Hauke Daempfling at the IGB Berlin

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.