Currently used digital signatures based on asymmetric cryptography will be vulnerable to quantum computers running Shor's algorithm. In this work, we propose a new quantum-assisted digital signature protocol based on symmetric keys generated by QKD, that allows signing and verifying messages in a simple way implementing an integration of currently available classical and quantum technologies. The protocol is described for a three-user scenario composed of one sender and two receivers. In contrast to previous schemes, it is independent of the message length. The security of the protocol has been analyzed, as well as its integrity, authenticity and non-repudiation properties.
Currently used digital signatures based on asymmetric cryptography will be vulnerable to quantum computers running Shor's algorithm. In this work, we propose a new quantum-assisted digital signature protocol based on symmetric keys generated by QKD, that allows signing and verifying messages in a simple way implementing an integration of currently available classical and quantum technologies. The protocol is described for a three-user scenario composed of one sender and two receivers. In contrast to previous schemes, it is independent of the message length. The security of the protocol has been analyzed, as well as its integrity, authenticity and non-repudiation properties.
One of the most important applications of cryptography is digital signature (DS), which aims to certify the provenance of a message as well as its authenticity, ensuring the nonrepudiation, unforgeability, and transferability of messages. However, the forthcoming advent of quantum computers poses a significant threat to classical signature schemes. In this work, an improved version of a novel quantum-assisted digital signature (QADS) solution will be presented, in which quantum keys generated by quantum key distribution (QKD) are used together with standard classical cryptographic functions to provide a hybrid system that integrates quantum and classical cryptography. The quantum keys enhance the security of the DS, allowing to sign messages with arbitrary lengths while maintaining a suitable DS length. The proposed solution could push the practical exploitation of QKD in a new application domain, leading to a more pervasive integration of quantum technology in realistic scenarios.
Digital signature (DS) is an essential application of cryptography, used to certify the provenance of a message and its authenticity, guaranteeing the non-repudiation, unforgeability, and transferability of messages. However, the forthcoming advent of quantum computation poses a significant threat to classical signature schemes. A possible solution could be the introduction of novel DS schemes based on the fundamental laws of quantum physics. Recently, several quantum DS (QDS) protocols have been proposed, even relying on the exploitation of off-the-shelf quantum key distribution (QKD) solutions. However, their efficiency and large signature size, uncorrelated to the size of the message to sign, represent the main limitation in their employment in a practical scenario. A trade-off solution could be a quantum-assisted DS (QADS), where the QKD technology is exploited together with classical cryptographic functions to achieve a stronger DS scheme, more resistant even to quantum attacks. We propose a generalized quantum-assisted digital signature (G-QADS) protocol based on a hybrid system, composed by the standard Wegman-Carter Message Authentication Code (WG-MAC) together with symmetric QKD keys, to enhance the security of the DS, allowing messages with arbitrary lengths to be signed while maintaining a suitable DS length. In this work, the G-QADS process is proposed for a three-party configuration (one signer and two verifiers), where the third participant is involved in the procedure just in the case of contention between the other two parties. The G-QADS protocol is then experimentally tested to prove its resilience to forging and non-repudiation attacks, demonstrating its capability in securing the message signature (with a success probability of the attacks <10 −18 ). The performance is experimentally tested exploiting QKD prototypes based on standard BB84 protocol with decoy states and polarization encoding, in a software-defined network (SDN) infrastructure supervised by a single SDN controller, which provides the management of both classical and quantum communication channels. The proposed solution could push the practical exploitation of QKD into a new application domain, leading to a more pervasive integration of quantum technology in realistic scenarios.
With the quantum computational paradigm rapidly developing across the world, new vulnerabilities on currently deployed cryptography protocols are to be taken in consideration. A possible answer to said vulnerabilities is using quantum technologies on cryptography. For a quantum-assisted cryptography protocol, key pairs can be generated via quantum state measurements. This protocol is known as quantum key distribution, of extended use for providing security against any algorithm-based attack to the keys. Ensured the key protection against eavesdroppers, a QKD-assisted protocol can focus its security analysis on party behaviour. Depending on the protocol rules and steps to follow, users can attempt attacks on it with the purpose of causing disagreement or misunderstanding between parties. In this work, we present a simulation environment for a hybrid, quantum-assisted digital signature (QDS) protocol. The configurations available for the simulated network as well as the digital signature protocol make it possible to design specific communication scenarios, such as attacks on the message integrity, forging and repudiation attempts or noisy communication across the quantum channels.
Quantum digital signatures can be used to authenticate classical messages in an information-theoretically secure way. Previously, a novel quantum digital signature for classical messages has been proposed and gave an experimental demonstration of distributing quantum digital signatures from one sender to two receivers. Some improvement versions were subsequently presented, which made it more feasible with present technology. These proposals for quantum digital signatures are basic building blocks which only deal with the problem of sending single bit messages while no-forging and non-repudiation are guaranteed. For a multi-bit message, it is only mentioned that the basic building blocks must be iterated, but the iteration of the basic building block still does not suffice to define the entire protocol. In this paper, we show that it is necessary to define the entire protocol because some attacks will arise if these building blocks are used in a naive way of iteration. Therefore, we give a way of defining an entire protocol to deal with the problem of sending multi-bit messages based on the basic building blocks and analyse its security.
Digital signatures are widely used for providing security of communications. At the same time, the security of currently deployed digital signature protocols is based on unproven computational assumptions. An efficient way to ensure an unconditional (information-theoretic) security of communication is to use quantum key distribution (QKD), whose security is based on laws of quantum mechanics. In this work we develop an unconditionally secure signature scheme that guarantees authenticity and transferability of arbitrary length messages in a QKD network. In the proposed setup, the QKD network consists of two subnetworks: (i) an internal network that includes the signer and with limitation on the number of malicious nodes and (ii) an external network that has no assumptions on the number of malicious nodes. A consequence of the absence of the trust assumption in the external subnetwork is the necessity of assistance from internal subnetwork recipients for the verification of message-signature pairs by external subnetwork recipients. We provide a comprehensive security analysis of the developed scheme, perform an optimization of the scheme parameters with respect to the secret key consumption, and demonstrate that the developed scheme is compatible with the capabilities of currently available QKD devices.
This paper introduces Generalized Quantum-assisted Digital Signature (GQaDS), an improved version of a recently proposed scheme whose information theoretic security is inherited by adopting QKD keys for digital signature purposes. Its security against forging is computed considering a trial-and-error approach taken by the malicious forger and GQaDS parameters are optimized via an analytical approach balancing between forgery and repudiation probabilities. The hash functions of the previous implementation are replaced with Carter-Wegman Message Authentication Codes (MACs), strengthening the scheme security and reducing the signature length. For particular scenarios where the second verifier has a safe reputation, a simplified version of GQaDS, namely deterministic GQaDS, can further reduce the required signature length, keeping the desired security strength.