Efficient Data Retrieval Over Encrypted Attribute-Value Type Databases in Cloud-Assisted Ehealth Systems

Abstract

In cloud-assisted electronic health (eHealth) systems, outsourced electronic health records (EHRs) have attribute-value type formats: an EHR corresponds to an entry with a unique identity and has multiple types of attribute values. Such formatted EHRs form an attribute-value type database, where both the attribute values and unique identities can serve as keywords for searching. Since EHRs are very sensitive, they are always encrypted before being outsourced, which makes retrieval of target EHRs by either identity or attribute value hard. Moreover, the EHRs are encrypted by different doctors, a researcher, who is delegated to research a certain kind of disease, cannot find out all corresponding EHRs due to the difference of encryption keys. In this article, we construct a triple dictionary index structure for the attribute-value type database to allow a researcher to retrieve encrypted EHRs by the identity and attribute value and to perform dynamic operations over them. We employ an identity server to assist doctors in generating encryption keys via an oblivious way. By doing so, the researcher can retrieve encrypted EHRs without leaking any information to the identity server. We analyze the security and evaluate the performance of our scheme to demonstrate that it achieves <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L$</tex-math></inline-formula> -adaptive security and forward security with high efficiency.