Insecurity of position-based quantum cryptography protocols against entanglement attacks

Understand

Recently, position-based quantum cryptography has been claimed to be unconditionally secure.

• In contrary, here we show that the existing proposals for position-based quantum cryptography are, in fact, insecure if entanglement is shared among two adversaries.
• Specifically, we demonstrate how the adversaries can incorporate ideas of quantum teleportation and quantum secret sharing to compromise the security with certainty.
• The common flaw to all current protocols is that the Pauli operators always map a codeword to a codeword (up to an irrelevant overall phase).