Quantum Dialogue Revisited

An entanglement-based quantum dialogue protocol Phys. Lett. A 328(2004)6 is proven to be insecure: that is, in the protocol an eavesdropper can steal the secret messages without being detected provided that he/she adopts the intercept-and-resend attack strategy. We modify the protocol, i.e. in the control mode, by introducing and randomly choosing two sets of measuring basis: the intercept-and-resend attack can be accordingly detected. Hence, within the present version two users can securely and simultaneously exchange their secret messages.