Dynamic searchable symmetric encryption (DSSE) has been widely recognized as a promising technique to delegate update and search queries over an outsourced database to an untrusted server while guaranteeing the privacy of data. Many efforts on DSSE have been devoted to obtaining a good tradeoff between security and performance. However, it appears that all existing DSSE works miss studying on what will happen if the DSSE client issues irrational update queries carelessly, such as duplicate update queries and delete queries to remove non-existent entries (that have been considered by many popular database system in the setting of plaintext). In this scenario, we find that (1) most prior works lose their claimed correctness or security, and (2) no single approach can achieve correctness, forward and backward security, and practical performance at the same time. To address this problem, we study for the first time the notion of robustness of DSSE. Generally, we say that a DSSE scheme is robust if it can keep the same correctness and security even in the case of misoperations. Then, we introduce a new cryptographic primitive named key-updatable pseudo-random function and apply this primitive to constructing ROSE, a robust DSSE scheme with forward and backward security. Finally, we demonstrate the efficiency of ROSE and give the experimental comparisons.

Outsourcing encrypted data to cloud servers that has become a prevalent trend among Internet users to date. There is a long list of advantages on data outsourcing, such as the reduction cost of local data management. How to securely operate encrypted data (remotely), however, is the top-rank concern over data owner. Liang et al. proposed a novel encrypted cloud-based data share and search system without loss of privacy. The system allows users to flexibly search and share encrypted data as well as updating keyword field. However, the search complexity of the system is of extreme inefficiency, O(n d)O(nd), where dd is the total number of system files and nn is the size of query formula. This article, for the first time, leverages the 'oblivious cross search' technology in public key searchable encryption context to reduce the search complexity to only O(nf(w))O(nf(w)), where f(w)f(w) is the number of files embedded with the 'least frequent keyword' ww. The new scheme maintains efficient encrypted data share and keyword field update as well. This article further revisits the security models for payload security, keyword privacy and search token privacy (i.e., search pattern privacy) and meanwhile, presents security and efficiency analysis for the new scheme.

Public-Index Predicate Encryption (PIPE) allows users to encrypt according to boolean predicates defined on arbitrary attributes. The expensive algebraic operations are the major efficiency obstacle for PIPE to be applied to mobile clouds. This paper proposes a general Online/Offline PIPE (OO-PIPE) framework to address this issue. First, we propose a generic transformation from a Large Universe PIPE (LUPIPE) secure against chosen plaintext attack (CPA) to OO-PIPE in the same security model. The challenge is to generate ciphertext without the knowledge of the associated ciphertext attributes in the offline phase. We address the challenge by identifying an interesting attribute-malleability property in many LU-PIPE schemes. The property allows an encryptor to efficiently malleate a ciphertext associated with one ciphertext attribute to any assigned ciphertext attribute. Second, we design a generic transformation from CPA-secure LU-PIPE to OO-PIPE secure against adaptively chosen ciphertext attack (CCA2), assuming the underlying LUPIPE has attribute-malleability and public-verifiability properties. The main obstacle here is that the online/offline mechanism endogenously implies forgery in the sense that a pre-computed ciphertext must be able to be efficiently malleated to the resulting ciphertext associated with a different ciphertext attribute and a plaintext, while any efficient valid ciphertext forgery is forbidden in CCA2 security. We circumvent this obstacle by employing a universally collision resistant Chameleon hash, namely, only the original encryptor can malleate the ciphertext to associate with different attributes and provide a hash collision of the ciphertext components.