ShadowFPE: New Encrypted Web Application Solution Based on Shadow DOM

Most of users hesitate to use third-party web applications because of security and privacy concerns. An ideal solution would be to allow apps to work with encrypted data, so that users might be more willing to provide just the encrypted version of their sensitive data. ShadowCrypt, proposed in CCS 2014, is the first and so far only solution that can achieve this by leveraging the encapsulation provided by Shadow DOM V0, without the need for the users to trust neither server nor client codes of web applications. Unfortunately, researchers have shown that ShadowCrypt is vulnerable to several attacks. Note that ShadowCrypt is no longer compliant to the updated W3C standard since 2015. Furthermore, some attacks on ShadowCrypt have been proposed. Hence, currently there is no effective and secure solution to guarantee the privacy of users. In this paper, we present ShadowFPE, a novel format-preserving encryption that makes use of a robust property in Shadow DOM to obtain a feasible solution. Compared with ShadowCrypt, ShadowFPE does not destroy the data format and makes the data usable in most of cloud web applications. We confirmed the effectiveness and security of ShadowFPE through case studies on web applications. Our results show that ShadowFPE is practical since it has low computational overhead and requires minimal modification in existing applications.