Secure quantum signature scheme without entangled state

The security of most quantum signatures cannot be proved with security model under chosen-message attack. No formal proof can prove that their security is fully dependent on the basic quantum theory. Based on the orthogonal quantum state and key-controlled quantum hash function, an arbitrated quantum signature is proposed. In this scheme, the signatory produces the quantum signature by quantum-encrypting the output of key-controlled quantum hash function. The signature verification is performed by decrypting the signed message and comparing the decrypted message with the output of the key-controlled quantum hash function. The security of the proposed scheme depends on the indistinguishability of the unknown quantum sequence. Its unforgeability can be formally proved with security model under chosen-message attack. Therefore, its security can be supported by the formal proof. On the other hand, in the proposed scheme, no entangled state is used. It also has better qubit efficiency as well.