Abstract—With the growing awareness of data privacy, more and more cloud users choose to encrypt their sensitive data before outsourcing them to the cloud. Search over encrypted data is therefore a critical function facilitating efficient cloud data access given the high data volume that each user has to handle nowadays. Inverted index is one of the most efficient searchable index structures and has been widely adopted in plaintext search. However, securing an inverted index and its associated search schemes is not a trivial task. A major challenge exposed from the existing efforts is the difficulty to protect user’s query privacy. The challenge roots on two facts: 1) the existing solutions use a deterministic trapdoor generation function for queries; and 2) once a keyword is searched, the encrypted inverted list for this keyword is revealed to the cloud server. We denote this second property in the existing solutions as one-time-only search limitation. Additionally, conjunctive multi-keyword search, which is the most common form of query nowadays, is not supported in those works. In this paper, we propose a public-key searchable encryption scheme based on the inverted index. Our scheme preserves the high search efficiency inherited from the inverted index while lifting the one-time-only search limitation of the previous solutions. Our scheme features a probabilistic trapdoor generation algorithm and protects the search pattern. In addition, our scheme supports conjunctive multi-keyword search. Compared with the existing public key based schemes that heavily rely on expensive pairing operations, our scheme is more efficient by using only multiplications and exponentiations. To meet stronger security requirements, we strengthen our scheme with an efficient oblivious transfer protocol that hides the access pattern from the cloud. The simulation results demonstrate that our scheme is suitable for practical usage with moderate overhead. I.

Abstract Public Key Encryption with Keyword Search (PEKS) scheme enable one to search the encrypted data with a keyword without revealing any information. The concept of a PEKS scheme was proposed by

Abstract: We introduce the technique of searchable encryption into the problem of secure two-party computation, and obtain novel approaches to accomplish Private Set Intersection (PSI). We present two protocols for PSI. The first one uses Baek’s Public Key Encryption with Multiple Keywords Search (MPEKS) as the basic tool, and the second one uses Gu’s Public Key Encryption with Keyword Search (PEKS) as the basic tool. Baek’s MPEKS supports multiple keywords search, but it requires expensive MapToPoint operations. Although the computation complexity of the MapToPoint operation can be reduced by new techniques, it indeed influences the efficiency. A natural method is to find a searchable encryption which requires no MapToPoint operations. So, we present the second protocol based on Gu’s PEKS. Gu’s PEKS does not support multiple keywords search, however, it still can help us to improve the efficiency of PSI significantly. We aim to achieve PSI in computationally asymmetric settings such as Cloud Computing, and both of our two protocols gain linear computation complexity for the client. We assume that m denotes the cardinality of the client’s input set. Concretely, in the protocol based on MPEKS, the client needs to compute m multiplications, m MapToPoint operations and one modular exponentiation; and in the protocol based on PEKS, the client only needs to compute m multiplications, m ordinary hashes, and one modular exponentiation to get the intersection. Both protocols satisfy privacy with respect to semi-honest behaviors.