Efficient Multi-User Indexing for Secure Keyword Search

Secure keyword search in shared infrastructures prevents stored documents from leaking confidential information to unauthorized users. We assume that a shared index provides confidentiality if it can only be used by users authorized to search all the documents contained in the index. We introduce the Lethe indexing workflow to improve query and update efficiency in secure keyword search. Lethe clusters together documents with similar sets of authorized users, and only creates shared indices for configurable volumes of documents with common users. Based on the published statistics of an existing dataset, we show that Lethe generates an indexing organization that simultaneously achieves both low search and update cost.