EncPDS: Encrypted Personal Data Stores via Key-Aggregate ID-Based Proxy Re-Encryption

Personal data stores (PDSs) are gaining attention as an alternative to the current systems used by tech giants to manage users' data. PDSs centrally manage user logs and data across services and enable data to be passed on to service providers in accordance with the user's own intentions. Using cloud servers to manage personal information is a natural choice from the perspectives of convenience and cost. Therefore, security is highly important in the PDS model. However, to the best of our knowledge, not enough research on encrypting PDS data has been conducted. This is because merely using conventional encryption schemes could compromise the functionality of PDSs. In this study, we developed a key-aggregate identity-based proxy re-encryption (KA-IB-PRE) scheme combining a key-aggregate cryptosystem technique with an identity-based proxy re-encryption scheme. Our approach is highly compatible with PDSs, and a system using KA-IB-PRE called EncPDS can construct a privacy-preserving model that meets their requirements. In particular, it offers advantages in privacy protection compared with existing methods, allowing for selective re-encryption of any data through key aggregation while keeping information about which data to re-encrypt hidden from the cloud.