Device-independent security of quantum cryptography against collective attacks

Phys Rev Lett. 2007 Jun 8;98(23):230501. doi: 10.1103/PhysRevLett.98.230501. Epub 2007 Jun 4.


We present the optimal collective attack on a quantum key distribution protocol in the "device-independent" security scenario, where no assumptions are made about the way the quantum key distribution devices work or on what quantum system they operate. Our main result is a tight bound on the Holevo information between one of the authorized parties and the eavesdropper, as a function of the amount of violation of a Bell-type inequality.