Bellare, Paterson, and Rogaway recently studied this question. They show a strong lower bound that in particular rules out even semantically secure public-key encryption in their model. However, Mironov and Stephens-Davidowitz recently introduced a new framework for solving such problems: reverse firewalls. A secure reverse firewall is a third party that ``sits between Alice and the outside world'' and modifies her sent and received messages so that even if the her machine has been corrupted, Alice's security is still guaranteed. We show how to use reverse firewalls to sidestep the impossibility result of Bellare et al., and we achieve strong security guarantees in this extreme setting.
Indeed, we find a rich structure of solutions that vary in efficiency, security, and setup assumptions, in close analogy with message transmission in the classical setting. Our strongest and most important result shows a protocol that achieves interactive, concurrent CCA-secure message transmission with a reverse firewall---i.e., CCA-secure message transmission on a possibly compromised machine! Surprisingly, this protocol is quite efficient and simple, requiring only four rounds and a small constant number of public-key operations for each party. It could easily be used in practice. Behind this result is a technical composition theorem that shows how key agreement with a sufficiently secure reverse firewall can be used to construct a message-transmission protocol with its own secure reverse firewall.Category / Keywords: cryptographic protocols / reverse firewalls, exfiltration, secure message transmission Date: received 4 Jun 2015, last revised 16 Feb 2016 Contact author: noahsd at gmail com Available format(s): PDF | BibTeX Citation Version: 20160216:214441 (All versions of this report) Short URL: ia.cr/2015/548 Discussion forum: Show discussion | Start new discussion