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 (AQS) schemes have been proposed. It was claimed that these AQS schemes could guarantee unconditional security. However, we show that they can be repudiated by the receiver Bob. To conquer this shortcoming, we construct an AQS scheme using a public board. The AQS scheme not only avoids being disavowed by the receiver but also preserves all merits in the existing schemes. Furthermore, we discover that entanglement is not necessary while all these existing AQS schemes depend on entanglement. Therefore, we present another AQS scheme without utilizing entangled states in the signing phase and the verifying phase. This scheme has three advantages: it does not utilize entangled states and it preserves all merits in the existing schemes; the signature can avoid being disavowed by the receiver; and it provides a higher efficiency in transmission and reduces the complexity of implementation.
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 (AQS) schemes have been proposed. It was claimed that these AQS schemes could guarantee unconditional security. However, we show that they can be repudiated by the receiver Bob. To conquer this shortcoming, we construct an AQS scheme using a public board. The AQS scheme not only avoids being disavowed by the receiver but also preserves all merits in the existing schemes. Furthermore, we discover that entanglement is not necessary while all these existing AQS schemes depend on entanglement. Therefore, we present another AQS scheme without utilizing entangled states in the signing phase and the verifying phase. This scheme has three advantages: it does not utilize entangled states and it preserves all merits in the existing schemes; the signature can avoid being disavowed by the receiver; and it provides a higher efficiency in transmission and reduces the complexity of implementation.
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.
Arbitrated quantum signature (AQS) schemes use quantum cryptography to ensure their security, and the schemes provide that the signature receiver verifies the signature with the arbitrator's assistance.Very recently, Gao and Choi found in some previous AQS schemes, the receiver, Bob can counterfeit the signer's signature under known message.Additionally, the paper gives the security analysis of the AQS scheme, and results show that not only the receiver, but also the attacker can forge the signature in the AQS scheme.Furthermore, the signer can successfully disavow any message she ever signed.To conquer these shortcomings, this paper gives a new AQS scheme without quantum entangled state; it uses special quantum logic gate and new quantum one-time pads to ensure its security.Compares with other previous AQS schemes, the new scheme has following advantages: (1) the new scheme guarantees the receiver and the attacker cannot forge the signature; (2) Because the new scheme does not use quantum entangled states, so it can reduce the complexity of implementation and provides a higher efficiency in transmission; (3) The receiver, Bob has verified the signature's integrity, so Alice cannot disavow her having signed message.
Arbitrated quantum signature (AQS) schemes aim at ensuring the authenticity of a message with the help of an arbitrator. Moreover, they aim at preventing repudiation, both from a sender that denies the origin of a message, and from a receiver who disavows its reception. Such protocols use quantum communication and are often designed to protect quantum messages. In this paper, we study four recently submitted AQS schemes and propose attacks on their security.
Firstly, we look at Zhang, Sun, Zhang and Jia's AQS scheme which aims at signing quantum messages with chained CNOT encryption. We show that the sender can repudiate her messages and make false allegation of reception. Moreover, we show that a dishonest receiver can forge signatures.
Secondly, we analyse Ding, Xin, Yang and Sang's AQS protocol to sign classical messages based on GHZ states. We show that both the sender and the receiver have simple repudiation strategies.
Thirdly, we study Lu, Li, Yu and Han's AQS scheme that uses controlled teleportation to protect quantum messages. We expose forgeries, false allegation attacks and the possibility of repudiation by both parties.
Fourthly, we focus on the AQS scheme by Zhang, Xin, Sun, Li and Li designed to sign classical messages without entangled states. We show that one can disavow the reception of messages, and that information-theoretic security is not achieved for other security goals.
Arbitrated quantum signatures (AQS), for signing quantum message, have been proposed. It was claimed that the AQS schemes could guarantee unconditional security. However, in this paper, we show that all the presented AQS protocols are insecure if quantum one-time pad encryption is used where the signer Alice can always successfully acquire Bob's secret key and disavow any of her signatures. The detailed attack strategies and security analysis are described. Furthermore, the original version of the protocols is revised and accordingly the security of the AQS protocols are improved. And meanwhile we present a method to against Alice's disavowal proposed by Gao et al. (arXiv:1106.4398v1).
Due to potential capability of providing unconditional security, arbitrated quantum signature (AQS) schemes, whose implementation depends on the participation of a trusted third party, received intense attention in the past decade. Recently, some typical AQS schemes were cryptanalyzed and improved. In this paper, we analyze security property of some AQS schemes and show that all the previous AQS schemes, no matter original or improved, are still insecure in the sense that the messages and the corresponding signatures can be exchanged among different receivers, allowing the receivers to deny accepting the signature of an appointed message. Some further improvement methods on the AQS schemes are also discussed.
In the most arbitrated quantum signatures (AQSs), the signers and verifiers need to perform the quantum key distribution protocols or some other protocols to share secret keys before signing a signature. In some schemes, the entangle states, which are not easily implemented, have to be prepared and distributed among the partners. Based on single photon and one-way functions, a new AQS scheme without entangled states is proposed. In our scheme, the signer generates a quantum signature on the classical message with his/her private key and the one-way function. The arbitrator communicates with the signer through a classical unencrypted channel. The signer and verifier need not perform the key distribution protocol before signing a message. On the other hand, without entangled states, our scheme can reduce the complexity of implementation. Then, our scheme is more efficient than the similar schemes. At the same time, our scheme is secure against forgery attack and disavowal attack.