At Paradox Engineering, we are deeply committed to the development of standard-based network solutions to build truly open City infrastructures. While we continue to endorse the benefits of interoperability for urban environments, these days we see a huge interest for standardized frameworks in other domains, specifically Covid-19 contact tracing. Many governments around the world are in a race to develop mobile apps to monitor Covid-19 cases and collect data to feed public healthcare decisions, as well as de-confinement and recovery actions. A team of researchers at the University of Oxford studied the effect of a Covid-19 contact tracing app in a City of about one million people: according to their simulation, if the app was used by 80% of current smartphone owners, it could be effective in slowing the spread of the virus. It might be useful even if fewer people downloaded it, preventing one infection for every one or two users. Promising real-life examples are TraceTogether in Singapore, COVIDSafe in Australia, or HaMagen in Israel. About one month ago Google and Apple jointly announced that they would integrate functionality to support Bluetooth-based apps directly into Android and iOS operating systems. Their decentralized reporting protocol is built on a combination of Bluetooth Low Energy technology and privacy-preserving cryptography. European governments have different views and fragmented approaches, with personal data protection under the spotlight as the greatest barrier to any solution proposed so far. In the resolution adopted on 17 April and during its plenary debate on 14 May, the European Parliament stressed that any digital measure against the pandemic must be in full compliance with data protection and privacy legislation. EU Commission recognized Covid-19 contact tracing apps, based on short-range technologies such as Bluetooth rather than geolocation, as the most promising from a public health perspective, and prepared guidelines and a toolbox for member states. And here is where standards come into play. Any solution based on proprietary technology is destined to add complexity and costs, jeopardizing community efforts: it happens in Smart Cities, it would happen in Covid-19 contact tracing. In order to be effective in breaking the virus transmission chains, a standardized framework should be preferred to allow full interoperability across countries, different proximity tracing and alert systems, while decentralized protocols happen to be more respectful of individual privacy. That’s why most European countries are eagerly looking at the developments of DP3T protocols (inspired by 3Ps: privacy, preserving, proximity), and projects such as COCOVID, the free and open initiative based on Big Data, Artificial Intelligence and digital technology that promises to contain Covid-19 resurgence while respecting data sovereignty. The newly established ETSI Industry Specification Group “Europe for Privacy-Preserving Pandemic Protection” is also working on a standard for secure smartphone-based Covid-19 contact tracing systems. But there might be another way. EIT Digital is developing an alternative solution using physical tokens, a technology already in use in logistic and banking applications. Physical tokens don’t require a smartphone and have only the minimal functionality needed for contact tracing, being small, robust, cheap, and little energy consuming. Their proximity technologies could include Bluetooth, but also the more accurate UltraWideBand, and allow for high levels of security. If successfully tested and implemented, they might represent a system to quickly inform possibly infected individuals while observing anonymity, voluntariness, transparency, security, temporality, and interoperability.