Provably Secure Self-Extractable Encryption

Abstract

There is an increasing demand of data sharing via cloud. Data privacy and secrecy protections are arguably the major challenges in such applications. It is widely suggested to encrypt outsourced data using advanced encryption primitives for flexible sensitive data sharing in cloud. In all existing asymmetric based systems, a subtle issue is that the data owner itself cannot read the encrypted and outsourced data. This raises a problem for the data owner when she needs to access the outsourced data but locally there is no copy in the clear text form. To cope with this problem, we formalize a new framework, referred to as Self-EXtractable Encryption (SEXE). In addition to the normal functionalities of an advanced encryption primitive, SEXE is equipped with a useful self-extractability. With this property, the data owner can always access her encrypted data. We propose a generic SEXE construction from any advanced encryption primitives. Following the proposed generic construction, we instantiate several typical SEXE systems, including Self-EXtractable Identity-Based Encryption (SEXIBE), Self-Extractable Attribute-Based Encryption (SXABE) in Key-Policy setting and in Ciphertext-Policy setting.