Paper 2025/1105

Low-cost anonymous reputation update for IoT applications

Abstract

This paper presents a novel zero-trust anonymous reputation update protocol for IoT crowd-sensing applications. We use a suite of cryptographic functions to achieve anonymity, including unlinkability of sensing reports to the principals that submit them, and of reports to one another, while enabling the infrastructure to reliably quantify the degree of trust expressed as a reputation level. The protocol is low-cost for the anonymous participant due to the use of cheap standard functions: low-exponent modular exponentiation and cryptographic hashing, which makes it quite suitable for IoT. Despite that, uniquely it does not require anonymous clients to trust the servers even if the latter could collude in an attempt to de-anonymise the former. Furthermore under the protocol, selective onboarding does not require trust either, as the gate keeper issues tickets assuredly blindly after examining the real user's credentials. On the other hand, reputation values versus time can be, and are, linked, enabling statistical analysis for accurately assessing reports without jeopardising anonymity. The protocol has been benchmarked on an off-the-shelf microcontroller broadly used in IoT solutions, with the latency measured at less than 30ms per round for the 4K RSA modulus that NIST recommends until the year 2035. The power drain has been calculated to be low enough for an implementation as a key fob using actual components and their manufacturer guaranteed data, with an embedded disc battery supporting the solution for in excess of 3 years.

Note: Typos fixed, abstract and conclusions revised, some minor changes to the main text.