SKC-CCCO: an encryption algorithm for quantum group signature

Quantum group signature (QGS) is an important variation in arbitrated quantum signature, and it can be used for special demands. However, most of existing QGS schemes suffer from different aspects of disavowals and forgeries owing to the employed encryption algorithm. We present a novel QGS scheme using single-key-controlled chained-CNOT and coin operator (SKC-CCCO), an encryption combined by key-controlled chained-CNOT and key-controlled coin operator. The former is sensitive to modifications of the message and the key due to its intrinsic chain effect, and the latter consists of random unitary operators instead of restricted Pauli operators in quantum one-time pad. It encrypts the ciphertext and the signer’s identity information to generate the group signature. Moreover, the quantum-walk-based teleportation is applied to transmit the ciphertext replica from the signer to the verifier for facilitating signature validity verification, in which advance preparation of the required entangled states and tricky joint measurements get averted. Additionally, the utilization of random number along with public board evades the verifier’s denials on the receipt and the integrality of the signature. Security and performance analyses show that the SKC-CCCO-based QGS scheme conforms to security requirements of a QGS and that the SKC-CCCO encryption possesses adequate keyspace and key sensitivity property against brute force attacks. Further, discussions exhibit the scheme has better efficiency in terms of transmission and key usage.