To solve the problem of blockchain interoperability, we propose an efficient decentralization oracle solution. We design a subgroup Schnorr multisignature for the off-chain aggregation mechanism of our system, which is proven to be secure and robust. Compared with threshold signature-based schemes, the subgroup multisignature-based scheme does not require the execution of the distributed key generation protocol, which greatly reduces off-chain costs. The on-chain verification of the Schnorr signature is also more efficient than the pairing-based signatures. Then, we design a fair incentive mechanism to encourage the oracle nodes to work hard to validate the external data, which is based on a repeated dynamic game. Compared with the existing incentive mechanisms, our mechanism considers the real actions of each node to determine whether it should be rewarded or penalized. We implement our system over the Ethereum blockchain, and the experiments show its good performance.

Fuzzy message detection is a novel cryptographic primitive in which the remote storage cloud can help the client carry out fuzzy detections with some false-positive rate. This primitive protects the privacy of clients and does not reveal exactly the matching messages to the untrusted cloud. However, the existing public-key-based schemes require many public keys to generate a single flag ciphertext. This introduces heavy costs in terms of public-key certificate management. In this paper, we propose an efficient identity-based fuzzy message detection method based on a novel identity-based online/offline encryption scheme. All heavy cost computation operations are carried out in the offline phase without the knowledge of the identities for each message, and the single flag ciphertext can be generated quickly with the message’s identities since only light cost computations are required in the online phase. We apply our scheme to the blockchain-based fuzzy message detection systems. Additionally, we design a new history indexing scheme based on Dodis’ verifiable random function and Schnorr’s signature. The transactions history and order of accessing storage cloud (storing and detecting messages) are indexed, and signed by each client. We provide the analysis of privacy guarantees and differential privacy requirements for our online/offline ID-FMD scheme, and implement our FMD system over the Fibos platform and the Huawei Elastic Cloud.

Updatable oblivious key management (UOKM) schemes are considered an important backbone of key management for large storage systems, which allows the key management server to periodically update all its clients’ ciphertexts stored in the remote storage cloud without interacting with the clients. All the encrypted data can only be decrypted by the current key (tag), which ensures security against forward and post compromise. In this paper, we propose two UOKM schemes: the first is public key-based, while the second is identity-based. Compared with Jarecki et al.'s UOKM scheme from oblivious pseudorandom functions, the implementations show that our chameleon hash-based schemes have faster updating processes. Moreover, our identity-based UOKM scheme does require ”heavy” public key certificate management and maintains a secure channel from the key management server to the storage cloud, which greatly enhances security and efficiency. Our proofs show that theunconditional obliviousandsecurityof our schemes are based on the security of chameleon hash functions.