Practical Quantum Tokens: Challenges and Perspectives

The concept of quantum tokens dates back alongside quantum cryptography to Stephen Wiesner's seminal work in 19831. Already this initial work proposes society-relevant applications such as secure quantum banknotes, which can be exchanged between a bank and a customer. This quantum currency is bas...

Impersonating Quantum Secrets over Classical Channels

We show that a simple eavesdropper listening in on classical communication between potentially entangled quantum parties will eventually be able to impersonate any of the parties. Furthermore, the attack is efficient if one-way puzzles do not exist. As a direct consequence, one-way puzzles are...

Multi-Copy Security in Unclonable Cryptography

Unclonable cryptography leverages the quantum no-cloning principle to copy-protect cryptographic functionalities. While most existing works address the basic single-copy security, the stronger notion of multi-copy security remains largely unexplored. We introduce a generic compiler that upgrades...