Quantum Secure Direct Communication Based on Secret Initial States of EPR Pairs

This paper proposes the protocol of Quantum Secure Direct Communization (QSDC) based on the secret initial Bell states which are shared by two legitimate communicators. Then, we analyze the security of the protocol against the intercept-and-resend attack and individual attack. It is unnecessary for the scheme to make odd particles especially which is used for detection of eavesdropping. Instead, it extracts some particles for detection from the travel sequence carrying secret messages. The results show that this protocol is secure and the information will not be leaked out even if the communication is forced to interrupt for eavesdropping.