Reduction of Information Leakage Related to the Access Patterns in Searchable Symmetric Encryption

Abstract

Cloud Computing is becoming a necessity with each passing day. As more and more Cloud Service Provider (CSP) are entering the market, the data security factor, which was the foremost concern, is still lurking around. As soon as the data is outsourced to a CSP, the original owner would depend on the CSP for its security. This may pose as a threat to the security of the data if the confidentiality of data of CSP is breached. Due to these issues, the clients are always concerned about their data being outsourced to cloud. Searchable encryption gives clients control over their sensitive data on the cloud. This thesis explores the effects of information leakage when access patterns are disclosed by searchable encryption scheme to an adversary. It is observed that in most of the existing schemes, a successful statistical attack can help the adversary learn the access pattern, provide him with the required document and reveal the underlying data. This paper addresses these issues by devising a SE scheme which leaks minimum possible information related to access pattern. The scheme uses an inverted indexbased approach to preserve the high search efficiency inherited from the inverted index while lifting the one-time-only search limitation of the previous solutions. Compared with the existing techniques, this solution uses keyword analysis to extract limited words from the documents based on their occurrence frequency. The test results demonstrate that our scheme is suitable for practical usage with minimal overhead.