In this paper, we provide the first treatment of MPC with graceful degradation of both security and corruptions. First of all, our protocols provide graceful degradation of security, i.e., different security guarantees depending on the actual number of corrupted parties: the more corruptions, the weaker the security guarantee. We consider all security properties generally discussed in the literature (secrecy, correctness, robustness, fairness, and agreement on abort). Furthermore, the protocols provide graceful degradation with respect to the corruption type, by distinguishing fully honest parties, passively corrupted parties, and actively corrupted parties. Security can be maintained against more passive corruptions than is possible for active corruptions. We focus on perfect security, and prove exact bounds for which MPC with graceful degradation of security and corruptions is possible for both threshold and general adversaries. Furthermore, we provide protocols that meet these bounds. This strictly generalizes known results on hybrid security and mixed adversaries.
Category / Keywords: cryptographic protocols / Multi-party computation, graceful degradation, hybrid security, mixed adversaries. Publication Info: Full version of a paper appearing at ICITS 2011 Date: received 24 Feb 2011 Contact author: clucas at inf ethz ch Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation Version: 20110228:223822 (All versions of this report) Short URL: ia.cr/2011/094