Wei-Chuen Yau

Cloud data sharing allows users to outsource data storage and management to external servers, but it also raises privacy concerns when data must remain encrypted while still supporting efficient search and fine-grained access control. Attribute-based encryption with keyword search (ABE-EKS) addresses this problem by combining searchable encryption with attribute-based access policies. However, existing schemes often focus on separate aspects such as expressive search, online/offline computation, revocation, or policy protection, while controlled trapdoor delegation and inequality-based keyword predicates are less commonly considered together in an implementation-oriented Type-3 pairing setting. This paper revisits the ABE-EKS framework of Yang et al. and adapts it to the Type-3 pairing setting. The construction follows the main structure of Yang et al.’s ABE-EKS scheme, but places the group elements in the appropriate source groups for asymmetric pairings. It further supports expressive access-control and keyword-search policies, Boolean keyword predicates, inequality comparisons, and trapdoor key delegation. We also analyse its security under the honest-but-curious cloud model and implement the scheme using the Apache Milagro Cryptographic Library (AMCL). Experimental results on the Enron Email dataset demonstrate the feasibility of the proposed construction for outsourced encrypted data-sharing scenarios.

Counterfeit artwork presents a significant risk to copyright holders and the economy. Without expertise in art, it is not straightforward to distinguish an artwork counterfeit from a genuine piece. This work designs and implements a reliable solution that enables users with near‐field communication‐enabled Android smartphones to verify artwork authenticity by accessing its respective certificate of authenticity stored in the Ethereum blockchain. To represent a physical artwork, the artwork image and metadata are stored in an inter‐planetary file system and minted as an ERC721 non‐fungible token to a smart contract deployed in Ethereum Rinkeby Testnet. The mobile app ArtProtect was developed to generate certificate of authenticity based on each non‐fungible token fetched through OpenSea Testnet API. Users access this information by scanning an near‐field communication tag embedded into the artwork. The content of the tag is signed by the respective artwork's artist and responsible agent by using Ethereum signing with their Ethereum wallet accounts. Through testing and analysis, the implemented work is secure, tamper‐evident, usable, flexible, and inexpensive to be applied to a real‐world scenario.

The public key encryption with keyword search (PEKS) scheme allows searches to be performed over ciphertext by a server in a public-key setting. The PEKS scheme suffers from a major drawback which is keyword guessing attack. A keyword guessing attack (KGA) allows the attacker to successfully guess the correct keyword encrypted in a searchable ciphertext and trapdoor. To overcome this vulnerability, security notions, such as keyword privacy and trapdoor privacy were introduced. Keyword privacy prevents any information leaked from the keyword itself, and similarly trapdoor privacy prevents any information leaked from the trapdoor side. A PEKS scheme that is secure against KGA should satisfy trapdoor privacy. In this paper, we compare various types of PEKS schemes in terms of their underlying computational hardness, system model, search function, security properties of keyword privacy and trapdoor privacy, and security against offline KGA and online KGA. From the comparison analysis, we highlight that trapdoor privacy and keyword privacy are essential for a PEKS scheme to be secure against KGA. Lastly, we draw some potential research directions.