  A digital signature is a mathematical scheme for demonstrating the
authenticity of a digital message or document. For signing quantum messages,
some arbitrated quantum signature schemes have being proposed. However, in the
existing literature, arbitrated quantum signature schemes depend on
entanglement. In this paper, we present two arbitrated quantum signature
schemes without utilizing entangled states in the signing phase and the
verifying phase. The first proposed scheme can preserve the merits in the
existing schemes. Then, we point out, in this scheme and the prior schemes,
there exists a problem that Bob can repudiate the integrality of the
signatures. To conquer this problem, we construct another arbitrated quantum
signature scheme without using quantum entangled states but using a public
board. The new scheme has three advantages: it does not utilize entangled
states while it can preserve all merits in the existing schemes; the
integrality of the signature can avoid being disavowed by the receiver; and, it
provides a higher efficiency in transmission and reduces the complexity of
implementation. Furthermore, we present a technique such that the quantum
message can keep secret to the arbitrator in a arbitrated quantum signature
scheme.
