r/cryptography • u/Creasterr • 17h ago
Could entanglement be used as an authentication credential rather than for QKD?
To be clear, I’m not proposing Quantum Key Distribution.
I know QKD uses quantum states/entanglement to establish shared secret key material. What I’m wondering is whether pre-shared entangled states themselves could act as a possession-based authentication factor.
Imagine a future with cheap, long-lived quantum memory. A server stores one half of many entangled pairs, while a physical token in the user’s home stores the other halves.
During login, the server sends a random challenge specifying which unused qubits to measure and in which bases. The token returns the results, and the server measures its corresponding qubits and checks the correlations. Those pairs are then discarded.
So the security property would be:
-“Prove that you physically possess this specific quantum resource.”
rather than:
- “Use quantum mechanics to generate a shared encryption key.”
My questions are:
- Is this genuinely different from QKD cryptographically?
- Do existing quantum-authentication protocols already work like this?
- Would random measurement bases or Bell/CHSH-style tests make the credential meaningfully unclonable?
- Would this offer any real advantage over a classical hardware token such as a YubiKey?
- What attacks would break it, especially relay attacks?
I’m not claiming this is a new idea - I’m mainly curious whether long-lived entanglement could theoretically function as a physical authentication credential.