Quantum key distribution with trusted quantum relay
  A trusted quantum relay is introduced to enable quantum key distribution links to form the basic legs in a quantum key distribution network. The idea is based on the well-known intercept/resend eavesdropping. The same scheme can be used to make quantum key distribution between several parties. No entanglement is required. 
H. Bechmann-Pasquinucci and A. Pasquinucci