Safety Analysis And Improvement Of Quantum Signature Scheme

In the near future, because the quantum signature can provide the unconditional security by the principles of quantum mechanics, it might be used widely as an alternative to the classical digital signature. Cryptanalysis on the existing schemes helps to estimate a protocol’s security level, find potential loopholes, and try to fix security flaws. This thesis points out the security issues on three quantum signature scheme and constructs a new arbitrated quantum signature scheme. Specifically, the major work finished is as follows.(1) This thesis points out that there are two security issues in an arbitrated quantum signature scheme with Bell states by constructing the valid attacks. First, a signer’s disavowal attack on this quantum signature scheme is proposed and the main reasons of this scheme being insecure the proposed attack is analyzed. Then, a receiver’s existential forgery on this quantum signature scheme is proposed; further, even if the Hadamard operation in the encryption method of this scheme is replaced with any 2nd-order unitary operation, this thesis points out that the proposed attack is still valid.(2) This thesis proposes a man-in-the-middle attack on a quantum signature scheme which based on a two-qubit quantum search algorithm, and points out this quantum signature scheme does not satisfy the security requirements it claimed. First, any attacker’s man-in-the-middle attack on this scheme is proposed. Then, this thesis points out that the man-in-the-middle attack can be exploited by both the signer and receiver,and enables them to disavow and forgery respectively. At last, this thesis analyzes the reasons of this scheme being insecure to the proposed man-in-the-middle attack.(3) This thesis proposes signers’ colluding attack on a quantum homomorphic signature scheme which uses the entanglement swapping. The main reasons why this scheme is vulnerable to the proposed colluding attack are analyzed from two aspects: the entanglement swapping and the verify of the schemes.(4) This thesis constructs an arbitrated quantum signature scheme, and its security is provided by the teleportion and the strengthened QOTP. This thesis also shows that this scheme can resist the signer’s disavowal attack and the receiver’s existential forgery.