In cloud storage, symmetric encryption is a common method to protect the confidentiality of volume data. One critical issue in symmetric encryption is the management of volume symmetric keys such as key generation, update and distribution. Many schemes have adopted hierarchical structures based on key derivation to generate and organize the keys. However, the efficient update of these derived and associated keys and the distribution of multiple derived keys have not been well studied. This paper mainly studies in-situ key update and traffic cost of key distribution. First, we redesign the key node structure of our binary key-derivation tree to provide the basis of the in-situ key update. Then, secure in-situ key update algorithms are proposed, in which forward secrecy and backward secrecy are guaranteed. Finally, we propose a minimal key set generation algorithm, which can effectively reduce the communication cost of key distribution. We also describe the key distribution and derivation process. Security analysis and extensive experimental evaluations show the proposed algorithms are secure, efficient and practical.

As the Internet of Vehicles (IoV) has become the critical part of Intelligent Vehicular Transportation Systems (IVTS), massive IoV entities (e.g., RSU, OBU, pedestrians’ mobile devices, etc.) get involved into IVTS. At present, one of the biggest challenges with IoV/IVTS is how to maintain a balance between security and privacy. The receivers need to be sure that they are receiving reliable messages from the origin and could trace or link the attacker’s identity, but the tracing or linking may work against the sender’s need for identity privacy. To solve the security and privacy problem, most of current works have proposed authentication solutions to provide anonymous, traceable and unlinkable schemes, which are still vulnerable to either Sybil attacks or quantum attacks. Therefore, we propose the blockchain-based post-quantum anonymous, traceable and linkable authentication scheme by utilizing NIST winner post-quantum algorithms and related post-quantum linkable ring signature. Grounded on the authentication scheme, we also develop key exchange mechanism, which help IoV entities perform efficient message authentication encryption/decryption during P2P communication and broadcast. The security analysis shows that our proposal is resistant to Sybil attack and provides other essential security characteristics including man-in-the-middle-proof and anti-replay. Finally, we perform detailed performance evaluation including each on-chain API execution time, the off-chain communication time and the on-board/on-chain storage requirements. To further evaluate the feasibility of our scheme in the IoV/IVTS environment, we also show the effectiveness of our proposal in a blockchain-based simulation study.

Data assured deletion can achieve the deletion of outsourced data without possessing it physically in the cloud environment. However, most of existing schemes are designed and implemented on the traditional platforms, which might be not applicable to the scenarios that data is accessed via resource-constrained mobile terminals due to the bandwidth and computation consumptions. In this paper, we present a counter-based data assured deletion scheme using TrustZone, which can restrict the number of times that data can be accessed by restricting the number of times the encryption key can be used on resource-constrained mobile terminals. For this purpose, we bind the number of reads of a secure file to a virtual monotonic counter to count the number of times the key has been used. Then the currently used number of times is compared with the pre-set number of times to check the use condition is satisfied or not. If the comparison result is false, the key is destroyed securely and a public deletion proof is generated. Additionally, we check the hash-based integrity of the key information to detect and prevent the replay attack. In our design, the key retrieve is one-time, which can save the traffic cost. We only use some basic and common cryptographic operations provided by the operating system, which can save the computation cost. The physical security functionalities provided by TrustZone are taken advantage of, which provides a higher security guarantee for our scheme. The simulation implementation and results show our scheme is feasible and practical for use.

Remote Attestation (RA) is a security service by which a Verifier (Vrf) can verify the platform state of a remote Prover (Prv). However, in most existing RA schemes, the Prv might be vulnerable to denial of service (DoS) attacks due to the interactive challenge-response methodology while there is no authentication about the challenge. Worse, many schemes cannot effectively detect mobile malware that can be inactive during the on-demand attestation launched by the Vrf. In this paper, we propose a self-measurement RA for SGX-based platforms, which can effectively mitigate DoS attacks and defend against mobile malware. To this end, a two-way identity authentication is first enforced between the Prv and Vrf with the help of a blockchain system, in which a shared session key is also generated. Secondly, trigger conditions of measurements on the Prv’s side are time points generated by the Prv self instead of Vrf’s requests. The Vrf can retrieve multiple self-measurement results during one execution of the protocol to monitor the Prv’s platform over a period of time continuously, which can detect mobile malware effectively. Our scheme utilizes SGX to provide the runtime protection for sensitive information such as session key, self-measurement code, time points of self-measurements, and self-measurement results, making a higher security guarantee. In addition, the session key, time points of self-measurements, and self-measurement code can be changed or upgraded, making our scheme more flexible and scalable. The simulation implementation and results show that our scheme is feasible and practical.

Consortium blockchain has been widely used in many application scenarios, where there is the demand for a universal user authentication and key exchange mechanism for all the application users in the system like Know Your Customer. Since current solutions heavily rely on traditional public-key cryptosystems that are vulnerable to attacks from quantum computers, we design and implement the first post-quantum (PQ) user authentication and key exchange system for consortium blockchain, which is integrated with all the PQ public-key (i.e., signature and encryption/KEM) algorithms in the current round of NIST call for national standard. Furthermore, we also provide chaincodes, related APIs together with client codes for further development. Last but not least, we perform a systematic evaluation on the performance of the system including the consumed time of chaincodes execution and the needed on-chain storage space. Based on the experiment results, we discuss the implications of our findings, which are helpful for the PQ blockchain-based application developers, the undergoing NIST call and the developers of the PQ algorithms.

It is straightforward to encrypt the outsourced data to protect its confidentiality using symmetric cryptography in cloud storage. How to control and restrict the use of the encryption key in data users’ devices becomes one of the critical issues. In most of existing time-based and policy-based schemes, the key cannot be stored locally in data users’ devices, making the traffic cost linear with the data access times as the key should be retrieved in each data access. In this paper, we propose a times-based scheme with Intel SGX to restrict the times the key can be used in the data user’s device to restrict the times of data access. The basic idea is to compare the current used times with the specified maximal times to determine whether the key can be used or not. To this end, we use a monotonic counter to count the times the key has been used. When the use condition is not satisfied, we destroy the key securely and generate public proof so that (i) the encrypted data cannot be accessed anymore, i.e., the data is deleted assuredly, (ii) the deletion can be verified. In addition, a hash-based integrity check approach is utilized to detect and prevent replay attacks. The experimental results on the implemented prototype show our scheme is feasible in practice.

Consortium blockchain has been widely used in different scenarios, where blockchain members demand that their uploaded data could be audited under their identities without exposing the data themselves. However, so far, no solution of privacy-preserving data auditing has been proposed. To address the problem, we propose zkrpChain, which focuses on protection of the integrity and privacy of the data uploaded by blockchain members while leaving their identities public. In zkrpChain, which is based on Hyperledger Fabric and Bulletproofs, both standard-range and arbitrary-range zero-knowledge range proofs generation and verification are supported. To improve the efficiency, the aggregation of multiple proofs and batch verification are also developed. For further development, we provide the client codes, chaincodes and related APIs. Finally, we conduct experiments to evaluate the performance of zkrpChaln, and the results show that the consumed time (in an 8-thread scheme) of chaincodes and needed on-chain space of zkrpChain are very close to Bulletproofs, which is evaluated in a single-machine environment.

A number of solutions have been proposed to tackle the user privacy-preserving issue. Most of existing schemes, however, focus on methodology and techniques from the perspective of data processing. In this paper, we propose a lightweight privacy-preserving scheme for user identity from the perspective of data user and applied cryptography. The basic idea is to break the association relationships between User identity and his behaviors and ensure that User can access data or services as usual while the real identity will not be revealed. To this end, an interactive zero-knowledge proof protocol of identity is executed between CSP and User. Besides, a trusted third-party is introduced to manage user information, help CSP to validate User identity and establish secure channel between CSP and User via random shared key. After passing identity validation, User can log into cloud platform as usual without changing existing business process using random temporary account and password generated by CSP and sent to User by the secure channel which can further obscure the association relationships between identity and behaviors. Formal security analysis and theoretic and experimental evaluations are conducted, showing that the proposal is efficient and practical.

Cloud storage allows users to store their data in a remote server to get rid of expensive local storage and management costs and then access data of interest anytime anywhere. A number of solutions have been proposed to tackle the verification of remote data integrity and retrievability in cloud storage systems. Most of existing schemes, however, do not support efficient data dynamics and/or suffer from security vulnerabilities when involving dynamic data operations. In this paper, we propose a dynamic proof of retrievability scheme supporting public auditability and communication-efficient recovery from data corruptions. To this end, we split up the data into data blocks and encode each data block individually using outer code and inner code before outsourcing so that i) an update inside any data block only affects a few codeword symbols and ii) communication-efficient data repair for a breakdown server can be achieved and communication overhead for small data corruptions within a server can be eliminated. Based on the encoded data blocks, we utilize rb23Tree to enforce the data sequence for dynamic operations, preventing the cloud service provider from manipulating data block to pass the integrity check in the dynamic scenario. Formal security analysis and extensive experimental evaluations are conducted, showing that the proposed scheme is practical for use in cloud storage systems.