IACR News item: 08 June 2015
Yevgeniy Dodis, Ilya Mironov, Noah Stephens-Davidowitz
ePrint ReportWhile Mironov and Stephens-Davidowitz demonstrated that reverse firewalls can be constructed for very strong cryptographic primitives (which are of mostly theoretical interest), we study reverse firewalls for perhaps the most natural cryptographic task: secure message transmission. 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 a small constant number of public-key operations. 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.
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