  In this paper, two information leakage resistant quantum dialogue (QD)
protocols over a collective-noise channel are proposed. Decoherence-free
subspace (DFS) is used to erase the influence from two kinds of collective
noise, i.e., collective-dephasing noise and collective-rotation noise, where
each logical qubit is composed of two physical qubits and free from noise. In
each of the two proposed protocols, the secret messages are encoded on the
initial logical qubits via two composite unitary operations. Moreover, the
single-photon measurements rather than the Bell-state measurements or the more
complicated measurements are needed for decoding, making the two proposed
protocols easier to implement. The initial state of each logical qubit is
privately shared between the two authenticated users through the direct
transmission of its auxiliary counterpart. Consequently, the information
leakage problem is avoided in the two proposed protocols. Moreover, the
detailed security analysis also shows that Eve's several famous active attacks
can be effectively overcome, such as the Trojan horse attack, the
intercept-resend attack, the measure-resend attack, the entangle-measure attack
and the correlation-elicitation (CE) attack.
