Universal quantum encryption for quantum signature using the swap test

We suggest a universal quantum encryption scheme suitable for use in quantum signature. The verifier in a variety of quantum signature protocols usually checks for the falsification of the quantum signature state pair by using a swap test. However, these quantum signature protocols are not secure against existential forgery attacks; We prove that the universal quantum encryption scheme proposed in this paper is secure against this type of forgery because it uses the non-(anti)commutativity of an arbitrary unitary operator. In addition, we demonstrate its use in a quantum signature. Moreover, the optimization of this encryption in comparison with other encryption schemes is presented.