Searchable encrypted data

Abstract

Data encryption is suggested to be used in data storage server such as mail and files system as it can ensure data security and reduce privacy risk. However, this induces that functionalities must be sacrificed for security, such as searching. For instance, if a client wants to retrieve encrypted mails which contain certain keywords from mail server, searching cannot be done without the loss of data confidentiality. That means encrypted data cannot be searched without decrypting it. Actually, there were papers to prove that encrypted data is searchable. One of those was proposed by Song et al. They claimed that their cryptographic schemes had several advantages. First of all, they were provably secure, in the sense that the untrusted server cannot learn anything about the plaintext with giving only the cipher text. Secondly, they provided query isolation for searches, meaning that the untrusted server cannot learn anything about the plaintext besides the search results. Thirdly, they provided controlled searching, so that the untrusted server cannot search for an arbitrary word without the user’s authorization. Fourthly, they support hidden queries, such that the user may ask the untrusted server to search for a secret word without revealing the word to the server. Finally, they are simple, fast and nearly no space and communication overhead. In our project, we implemented a secure email system with Song et al’s idea and tried to proof that whether their searching techniques on encrypted data are work or not.