Electronic patient record (EPR) gains popularity in the health care system with easy availability and usually employs searchable encryption to guarantee both record confidentiality and record retrieval. However, traditional searchable encryption schemes cost a linear complexity of database and even reveals the query index. Both problems hinder EPR applications thereby balancing privacy and search efficiency becomes challenging. In this article, we design a cryptographically searchable EPR system named FastPRS which supports strong privacy and high performance. FastPRS is built on top of online/offline puncturable search (OOPS), a newly defined primitive which splits the search process into the offline phase and the online phase and embeds an index in puncturable pseudorandom sets. Leveraging a combination of linearly homomorphic encryption and oblivious transfer, the query index is punctured. OOPS, therefore, hides the query index obliviously and reduces the search complexity to a sublinear size. We also implement a FastPRS prototype system that supports more than 60 000 keywords and evaluation results show that FastPRS optimizes the search efficiency to 417 search operations per millisecond.

The concept of time release provides a new mode of sending information to the future, where the message will be available after a certainly specified period. Time-release encryption (TRE), as a promising approach, has a widespread releasing application and ensures data confidentiality. TRE relies on two main frameworks, one based on the time-lock puzzle and the other based on a trusted third party, while this primitive is impeded by frameworks’ unreliability limitations and time disclosure. We present ReleaseSC, a decentralized and privacy-aware system that combines smart contract with TRE. ReleaseSC leverages a novel three-part architecture that harmonizes time release and contracts, enabling efficient time-hidden smart contract. Our prototype is with reasonable performance through EVM evaluations on both private chain and official test network. ReleaseSC is built on the top of a new cryptographic notion named ID-based TRE that supports a flexible time policy and preserves the to-be-released time. We propose an ID-based TRE instantiation and show rigorous security analysis in formal security models. The insight from ReleaseSC will open more possibilities to address security issues in hybridized cryptography-blockchain systems.

Encrypted retrieval ensures the secure retrieval over the encrypted data without sacrificing the confidentiality. Its applications in the database systems have brought this primitive under the spotlight. Once the malicious sender sends the wrong message, conventional encrypted retrieval is arduous to provide message-moderation and even abuse reporting arises when any receiver is allowed to fabricate and convince a malicious message. We introduce the idea of searchable message-moderation, a newly exquisite framework named CleanSE that enables the system to simultaneously provide encrypted retrieval and fallacious reporting resistance. In a nutshell, CleanSE is achieved via a securely technical combination of asymmetric message franking and searchable encryption. We design two CleanSE schemes. The first, calledRecon, leverages designated verifier signatures to generate a report proof such as to prevent fallacious report and undeniability, and assists with designated-server searchable encryption to protect confidentiality and privacy. Our improved scheme is calledReclean. Compared withRecon,Recleanadds an additional algorithm,$\mathsf {Clean}$, to filter forged message and employs asymmetric message franking to provide stronger deniability and accountability. We implement and evaluate prototype of our CleanSE system to highlight its feasibility and practicality.

Internet of Things (IoT) makes great development and gains popularity with a mature combination with cloud computing. Plaintext data can be encrypted when data owners try to secure the confidentiality, while the encrypted data retrieval can be achieved by a cryptographic primitive named searchable encryption. Public-key encryption with keyword search (PEKS) is built on the asymmetric setting, however, the “honest-but-curious” assumption in PEKS creates challenges on the search reliability when malicious behaviors happen. It is nontrivial to enable the reliable search while preserving keyword privacy, as users who have paid need to receive either correct-and-wanted results or compensations. In this work, we apply blockchain to resolve this problem and design SearchBC, a blockchain-based PEKS framework supporting private, reliable, and fair encrypted search over the asymmetric setting. SearchBC is built on top of the blockchain and a keyword server to allow fairness in transactions and keyword preprocessing. We present a SearchBC instantiation and formally prove its security under the newly defined security model. SearchBC guarantees that search operations are fair and reliable and that the used keyword keeps privacy. The implementation results show that SearchBC provides a feasible means with reasonable communication and computation costs.