Secure Arbitrated Quantum Signature Scheme with Bell State

Recent researches on quantum signatures has no formal proof. Based on the Bell state and key-controlled hash function, an arbitrated quantum signature (AQS) scheme with formal proof is presented. In this scheme, the signer gets the quantum signature by encoding/encrypting Bell states, the encoded/encrypted states are swapped according to the protocol. The signature verification is performed by a trusted arbitrator. Arbitrator decoding/decrypting the swapped quantum states and comparing the decrypted message with the output of the key-controlled hash function to verify the validity of the signature. The security proof of the scheme reduces to the fundamental assumption of quantum mechanics: The indistinguishability of any two unknown quantum states. And its unforgeability can be formally proved with a security model under a chosen-message attack. Therefore, its security can be supported by a formal proof.