Abstract
This paper closes the question of the possibility of two-round MPC protocols achieving different security guarantees with and without the availability of broadcast in any given round. Cohen et al. [CGZ20] study this question in the dishonest majority setting; we complete the picture by studying the honest majority setting. In the honest majority setting, given broadcast in both rounds, it is known that the strongest guarantee—guaranteed output delivery—is achievable [GLS15]. We show that, given broadcast in the first round only, guaranteed output delivery is still achievable. Given broadcast in the second round only, we give a new construction that achieves identifiable abort, and we show that fairness—and thus guaranteed output delivery—are not achievable in this setting. Finally, if only peer-to-peer channels are available, we show that the weakest guarantee—selective abort—is the only one achievable for corruption thresholds t> 1 and for t= 1 and n= 3. On the other hand, it is already known that selective abort can be achieved in these cases. In the remaining cases, i.e., t= 1 and n≥ 4, it is known [IKP10, IKKP15] that guaranteed output delivery (and thus all weaker guarantees) are possible.
| Original language | English |
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| Title of host publication | Advances in Cryptology – CRYPTO 2021 : Proceedings |
| Number of pages | 30 |
| Publisher | Springer |
| Publication date | 2021 |
| Pages | 155-184 |
| ISBN (Print) | 978-3-030-84244-4 |
| ISBN (Electronic) | 978-3-030-84245-1 |
| DOIs | |
| Publication status | Published - 2021 |
| Event | Annual International Cryptology Conference - Virtual Duration: 16 Aug 2021 → 20 Aug 2021 https://link.springer.com/conference/crypto |
Conference
| Conference | Annual International Cryptology Conference |
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| Location | Virtual |
| Period | 16/08/2021 → 20/08/2021 |
| Internet address |