Processing Over Encrypted Data: Between Theory and Practice

Data encryption is a common approach to protect the confidentiality of users' data. However, when computation is required, the data must be decrypted before processing. The decryption-for-processing approach causes critical threats. For instance, a compromised server may lead to the leakage of data or cryptographic keys. On the other hand, data owners are concerned since the data is beyond their control. Thus, they look for mechanisms to achieve strong data protection. Accordingly, alternatives for protecting data become essential. Consequently, the trend of processing over encrypted data starts to arise along with a rapidly growing literature. This paper surveys applications, tools, building blocks, and approaches that can be used to directly process encrypted data (i.e., without decrypting it). The purpose of this survey is to provide an overview of existing systems and approaches that can be used to process encrypted data, discuss commercial usage of such systems, and to analyze the current developments in this area