@inproceedings{8322,
  abstract     = {Reverse firewalls were introduced at Eurocrypt 2015 by Miro-nov and Stephens-Davidowitz, as a method for protecting cryptographic protocols against attacks on the devices of the honest parties. In a nutshell: a reverse firewall is placed outside of a device and its goal is to “sanitize” the messages sent by it, in such a way that a malicious device cannot leak its secrets to the outside world. It is typically assumed that the cryptographic devices are attacked in a “functionality-preserving way” (i.e. informally speaking, the functionality of the protocol remains unchanged under this attacks). In their paper, Mironov and Stephens-Davidowitz construct a protocol for passively-secure two-party computations with firewalls, leaving extension of this result to stronger models as an open question.
In this paper, we address this problem by constructing a protocol for secure computation with firewalls that has two main advantages over the original protocol from Eurocrypt 2015. Firstly, it is a multiparty computation protocol (i.e. it works for an arbitrary number n of the parties, and not just for 2). Secondly, it is secure in much stronger corruption settings, namely in the active corruption model. More precisely: we consider an adversary that can fully corrupt up to 𝑛−1 parties, while the remaining parties are corrupt in a functionality-preserving way.
Our core techniques are: malleable commitments and malleable non-interactive zero-knowledge, which in particular allow us to create a novel protocol for multiparty augmented coin-tossing into the well with reverse firewalls (that is based on a protocol of Lindell from Crypto 2001).},
  author       = {Chakraborty, Suvradip and Dziembowski, Stefan and Nielsen, Jesper Buus},
  booktitle    = {Advances in Cryptology – CRYPTO 2020},
  isbn         = {9783030568795},
  issn         = {1611-3349},
  location     = {Santa Barbara, CA, United States},
  pages        = {732--762},
  publisher    = {Springer Nature},
  title        = {{Reverse firewalls for actively secure MPCs}},
  doi          = {10.1007/978-3-030-56880-1_26},
  volume       = {12171},
  year         = {2020},
}