İndexing of XML-based encrypted medical documents in worm storage

Abstract

Since the medical records are increasingly stored in electronic forms, especially in XML based documents, the storage devices for these records must preserve their trustworthiness. The regularity requirements rely on storing the critical data in Write-Once- Read-Many (WORM) storage devices to prevent them from easy modification. The XML documents stored in the WORM storage may also be encrypted in order to protect the sensitive data, and satisfy the security requirements. Efficient access of the large volume of records requires the use of direct access mechanisms such as indexes. Relying on indexes for accessing records could, however, provide a means for effectively altering or deleting records, even those stored in WORM storage. In this study, we propose a novel indexing structure and an encryption schema for encrypted medical XML documents stored in WORM storage structures. The proposed indexing method expedites projection, selection and join operations on encrypted medical XML records stored in WORM storages, and uses Generalized Hash Tree (GHT) data structure. Also, medical XML documents are stored with a novel encryption schema which combines traditional encryption techniques with order preserving encryption schema (OPES). In the literature so far, there are only some studies on indexing techniques for some ordinary documents such as electronic mail, financial statements, quality assurance documents which all stored in WORM structures, and these indexing structures only manage simple insert and search algorithms. Finally, we demonstrate that the proposed system gives satisfactory performance.