[en] We present a quantum signature scheme based on a two-qubit quantum search algorithm. For secure transmission of signatures, we use a quantum search algorithm that has not been used in previous quantum signature schemes. A two-step protocol secures the quantum channel, and a trusted center guarantees non-repudiation that is similar to other quantum signature schemes. We discuss the security of our protocol. (paper)

[en] We present a quantum signature scheme for a participant attack using only Pauli operators. The arbitrator verifies the signature and serves to prevent the denial of participants as well as the existing arbitrated quantum signature. Conversely, Bob’s existential forgery and Alice’s disavowal, which are reported to be a shortcoming of Pauli operators, are not allowed. This simplifies the structure and increases the efficiency of communication.

[en] In challenge-response authentication, the claimants are required to prove that they are legitimate users while minimizing the exposure of their confidential information. We propose a quantum challenge-response identification protocol using single qubit unitary operators that utilizes the mechanism of challenge-response, unlike most existing protocols that use (one-time) password authentication. We utilized the commutation relations of single qubit unitary operators to design this protocol that ensures the security of confidential information during identification in a quantum computing environment. For security analysis, we estimated the average fidelity of two quantum states after performing operations with the unitary operators based on the random numbers generated by two users. Subsequently, we evaluated the amount of information acquired by an eavesdropper to show that the proposed protocol is robust against impersonation and intercept-measurement attacks. Finally, we described the advantages of the protocol by comparing it with the existing quantum identification protocols. (paper)