Distributed storage plays an essential role in realizing robust and secure data storage in a network over long periods of time. A distributed storage system consists of a data owner machine, multiple storage servers and channels to link them. In such a system, secret sharing scheme is widely adopted, in which secret data are split into multiple pieces and stored in each server. To reconstruct them, the data owner should gather plural pieces. Shamir's (k, n)-threshold scheme, in which the data are split into n pieces (shares) for storage and at least k pieces of them must be gathered for reconstruction, furnishes information theoretic security, that is, even if attackers could collect shares of less than the threshold k, they cannot get any information about the data, even with unlimited computing power. Behind this scenario, however, assumed is that data transmission and authentication must be perfectly secure, which is not trivial in practice. Here we propose a totally information theoretically secure distributed storage system based on a user-friendly single-password-authenticated secret sharing scheme and secure transmission using quantum key distribution, and demonstrate it in the Tokyo metropolitan area (≤90 km).
Distributed storage plays an essential role in realizing robust and secure data storage in a network over long periods of time. A distributed storage system consists of a data owner machine, multiple storage servers and channels to link them. In such a system, secret sharing scheme is widely adopted, in which secret data are split into multiple pieces and stored in each server. To reconstruct them, the data owner should gather plural pieces. Shamir's (k, n)-threshold scheme, in which the data are split into n pieces (shares) for storage and at least k pieces of them must be gathered for reconstruction, furnishes information theoretic security, that is, even if attackers could collect shares of less than the threshold k, they cannot get any information about the data, even with unlimited computing power. Behind this scenario, however, assumed is that data transmission and authentication must be perfectly secure, which is not trivial in practice. Here we propose a totally information theoretically secure distributed storage system based on a user-friendly single-password-authenticated secret sharing scheme and secure transmission using quantum key distribution, and demonstrate it in the Tokyo metropolitan area (≤90 km).
Distributed storage plays an essential role in realizing robust and secure data storage in a network over long periods of time. A distributed storage system consists of a data owner machine, multiple storage servers and channels to link them. In such a system, secret sharing scheme is widely adopted, in which secret data are split into multiple pieces and stored in each server. To reconstruct them, the data owner should gather plural pieces. Shamir's (k, n)-threshold scheme, in which the data are split into n pieces (shares) for storage and at least k pieces of them must be gathered for reconstruction, furnishes information theoretic security, that is, even if attackers could collect shares of less than the threshold k, they cannot get any information about the data, even with unlimited computing power. Behind this scenario, however, assumed is that data transmission and authentication must be perfectly secure, which is not trivial in practice. Here we propose a totally information theoretically secure distributed storage system based on a user-friendly single-password-authenticated secret sharing scheme and secure transmission using quantum key distribution, and demonstrate it in the Tokyo metropolitan area.
Abstract Secret sharing, as an important cryptographic technique, effectively reduces the risk of single points of failure and centralized leakage by distributing secret information across multiple independent entities. With the widespread application of cloud computing and cloud storage, achieving long-term secure storage and controllable recovery of sensitive data in untrusted cloud environments has become a critical issue. Traditional cloud storage solutions face potential risks of security degradation and privacy exposure under long-term operation and future quantum computing threats. This paper proposes a quantum secret sharing (QSS) scheme for cloud storage scenarios, combining the threshold secret sharing with quantum secure communication and quantum information processing to achieve distributed storage and secure reconstruction of secret information across multiple cloud servers. A quantum identity authentication mechanism is introduced to the authenticated user based on a quantum sequence. This protocol enhances the long-term security of the system during the storage phase through threshold distribution and proactive share refreshing mechanisms, and utilizes quantum states to complete the secure reconstruction of secrets during the recovery phase. Additionally, this scheme avoids direct interaction between cloud servers, improving the security in untrusted cloud environments. Security analysis shows that this protocol can effectively resist threats such as external eavesdropping and internal collusion.
The quantum key distribution (QKD) network with Vernam's one-time pad encryption and secret sharing are powerful security tools to realize an information theoretically secure (ITS) distributed storage system. In the work of Fujiwaraet al., a single-password-authenticated secret sharing (SPSS) scheme based on the QKD network and Shamirs secret sharing was experimentally demonstrated; it confirmed ITS data transmission, storage, authentication, and integrity. To achieve data integrity, an ITS message authentication code (MAC) tag is employed, and a data owner of the secret sharing performs both the MAC tag generation and verification. However, for a scenario in which the data owner and end users are different entities, the above approach may not work, since the data owner can cheat the end users. In this article, we resolve this problem by proposing an ITS integrity protection scheme employing a third-party verification with time-stamp. The ITS integrity protection is realized by two steps: integrity check by the data owner at data reconstruction and data integrity certification by the data owner, the end user, and the third-party verifier using a MAC based on universal2hash function and random number provided from the QKD network. In addition to introducing the third-party verifier, we institute “a trusted calculator,” which computes shares of the data and MAC tags and sends MAC tags to the third-party verifier. The random number used in calculation is stored in the trusted calculator. We implement this scheme on the SPSS system installed in the Tokyo QKD Network.
Abstract Supercomputers, quantum computers, other computers, and algorithmic advancements that can break cryptographic systems currently in use are becoming a reality. For information that requires long-term confidentiality (e.g. national security, military security, genomic data etc.), the threat of eavesdropping must be seriously considered. The leakage of such information would not only cause temporary confusion but would also have serious repercussions for future generations. Part of such important data are already being exchanged over the Internet using cryptography that is not resistant to quantum computers. Considering the possibility of harvest attacks on information that must be kept secret for centuries, developing a technology that can immediately eliminate the risk of eavesdropping in principle is desirable. In response to these demands, we previously developed an information-theoretically secure method for data transmission, storage, recovery, and authentication with a single password using a quantum key distribution network called a quantum secure cloud. We now apply this technology to develop an information-theoretically secure long-distance data-relay function and succeed in developing a distributed data-relay simulator that is compatible with current quantum key distribution networks. The throughput of this protocol is more than 10 Mbps for 10 MB data, so it can be applied to practical use.
With the increasing prominence of data security in cloud storage, we propose a practical and robust cloud storage scheme, which uses quantum random numbers as encryption keys, disperses the keys using Shamir’s secret sharing scheme, applies erasure coding to the ciphertext, and securely transmits the data through quantum key distribution protected networks to the distributed clouds. This system offers several key advantages, including quantum-level security, fault tolerance, and storage space saving. To validate its feasibility, we conduct comprehensive experimental tests covering essential functionalities such as encryption/decryption, key preservation, and data storage. By successfully demonstrating the effectiveness of our proposal, we aim to accelerate the application of quantum technology in cloud storage.
Storing data in the form of quantum states on cloud servers can significantly enhance storage efficiency. The storage and sharing of quantum data on cloud servers necessitate consideration of security issues. An ingenious solution is to store data in the form of ciphertext on cloud servers. When data needs to be shared with users, the cloud server performs a second encryption on the data ciphertext and sends the doubly encrypted ciphertext to the users. Users can decrypt and obtain the data itself using their private keys. This process can be regarded as the transformation of the data owner’s ciphertext into a shared ciphertext by a third party (the cloud server). This study proposes a new quantum data sharing scheme for cloud servers. One of our main contributions is the realization of sharing specific data with users who have appropriate permissions (satisfying certain attribute-based conditions). The security of the scheme is demonstrated through key analysis, plaintext analysis, first-level ciphertext analysis, and second-level ciphertext analysis.