Leakage-abuse Attacks Against Forward Private Searchable Symmetric Encryption
Khosro Salmani, Ken Barker · Advances in Science Technology and Engineering Systems Journal · 2022
Access pattern leakage Search pattern leakage Data privacy Leakage-abuse attacksDynamic Searchable Symmetric Encryption (DSSE) methods address the problem of securely outsourcing\updating private data into a semi-trusted cloud server.Furthermore, Forward Privacy (FP) notion was introduced to limit data leakage and thwart the related attacks on DSSE approaches.FP schemes ensure previous search queries cannot be linked to future updates and newly added files.Since FP schemes use ephemeral search tokens and one-time use index entries, many scholars conclude that privacy attacks on traditional SSE schemes do not apply to SSE approaches that support forward privacy.However, to obtain efficiency, all FP approaches accept a certain level of data leakage, including access pattern leakage.Here, we introduce two new attacks on forward-private schemes.We demonstrate that it is still plausible to accurately unveil the search pattern by reversing the access pattern.Afterward, the attackers can exploit this information to uncover the search queries and consequently the documents.We also show that the traditional privacy attacks on SSE schemes are still applicable to schemes that support forward privacy.We then construct a new DSSE approach that supports parallelism and obfuscates the search and access pattern to thwart the introduced attacks.Our scheme is cost-efficient and provides secure search and update.Our performance analysis and security proof demonstrate our approach's practicality, efficiency, and security.