Conflict increasingly takes place online. And also aid providers, hospitals, and humanitarian organisations increasingly rely on digital infrastructure like servers and networks. In the physical world, the emblems of the Red Cross, Red Crescent, and Red Crystal identify protected sites such as hospitals, but no equivalent signal exists in cyberspace. The Digital Emblem project is building that missing signal: a machine-readable marker identifying digital infrastructure as protected under International Humanitarian Law.

The Digital Emblem is a protocol with an unusual threat model. Most security systems are built for the people you want to let in. The Digital Emblem is built for the people you want to keep out. Its most important users are those who want to attack digital infrastructure. The Digital Emblem project’s success hinges on whether attackers are willing to take the new signal into account. The Digital Emblem cannot put offensive operations at risk, and it must be verifiable and trustworthy.

Initiated by the International Committee of the Red Cross (ICRC) in 2020, the project has progressed far. In 2024, all states party to the Geneva Conventions adopted a resolution strengthening the ICRC’s mandate to develop the Emblem. In 2025, standardisation work began at the IETF and ITU in parallel. The same year, a Digital Emblem prototype developed at ETH Zurich was first tested with NATO in a military exercise.

This talk covers where the project stands, the requirements a Digital Emblem must meet, the adversarial constraints that shaped them, and how both led to ADEM, the prototype for a Digital Emblem currently being tested.

About the speaker

Felix Linker

Security Researcher at ETH Zurich

Felix Linker is a security researcher at ETH Zurich. He collaborates with the International Committee of the Red Cross on the Digital Emblem project, and is the lead designer of ADEM, a design for a Digital Emblem. Felix specializes in the design and formal verification of protocols and systems with security guarantees in general. He obtained his Doctorate in the Information Security Group at ETH Zurich, where he researched protocol design and verification. In particular, he is one of the leading experts for the Tamarin prover, a state-of-the-art tool that can formally reason about protocol security. Felix is also active in the Internet Engineering Task Force where he works on the standardization and formal analysis of protocols.
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