TY - GEN
T1 - Separating two-round secure computation from oblivious transfer
AU - Applebaum, Benny
AU - Brakerski, Zvika
AU - Garg, Sanjam
AU - Ishai, Yuval
AU - Srinivasan, Akshayaram
N1 - Publisher Copyright:
© Benny Applebaum, Zvika Brakerski, Sanjam Garg, Yuval Ishai, and Akshayaram Srinivasan.
PY - 2020/1
Y1 - 2020/1
N2 - We consider the question of minimizing the round complexity of protocols for secure multiparty computation (MPC) with security against an arbitrary number of semi-honest parties. Very recently, Garg and Srinivasan (Eurocrypt 2018) and Benhamouda and Lin (Eurocrypt 2018) constructed such 2-round MPC protocols from minimal assumptions. This was done by showing a round preserving reduction to the task of secure 2-party computation of the oblivious transfer functionality (OT). These constructions made a novel non-black-box use of the underlying OT protocol. The question remained whether this can be done by only making black-box use of 2-round OT. This is of theoretical and potentially also practical value as black-box use of primitives tends to lead to more efficient constructions. Our main result proves that such a black-box construction is impossible, namely that non-black-box use of OT is necessary. As a corollary, a similar separation holds when starting with any 2-party functionality other than OT. As a secondary contribution, we prove several additional results that further clarify the landscape of black-box MPC with minimal interaction. In particular, we complement the separation from 2-party functionalities by presenting a complete 4-party functionality, give evidence for the difficulty of ruling out a complete 3-party functionality and for the difficulty of ruling out black-box constructions of 3-round MPC from 2-round OT, and separate a relaxed “non-compact” variant of 2-party homomorphic secret sharing from 2-round OT.
AB - We consider the question of minimizing the round complexity of protocols for secure multiparty computation (MPC) with security against an arbitrary number of semi-honest parties. Very recently, Garg and Srinivasan (Eurocrypt 2018) and Benhamouda and Lin (Eurocrypt 2018) constructed such 2-round MPC protocols from minimal assumptions. This was done by showing a round preserving reduction to the task of secure 2-party computation of the oblivious transfer functionality (OT). These constructions made a novel non-black-box use of the underlying OT protocol. The question remained whether this can be done by only making black-box use of 2-round OT. This is of theoretical and potentially also practical value as black-box use of primitives tends to lead to more efficient constructions. Our main result proves that such a black-box construction is impossible, namely that non-black-box use of OT is necessary. As a corollary, a similar separation holds when starting with any 2-party functionality other than OT. As a secondary contribution, we prove several additional results that further clarify the landscape of black-box MPC with minimal interaction. In particular, we complement the separation from 2-party functionalities by presenting a complete 4-party functionality, give evidence for the difficulty of ruling out a complete 3-party functionality and for the difficulty of ruling out black-box constructions of 3-round MPC from 2-round OT, and separate a relaxed “non-compact” variant of 2-party homomorphic secret sharing from 2-round OT.
KW - Oblivious transfer
KW - Oracle separation
KW - Secure multiparty computation
UR - http://www.scopus.com/inward/record.url?scp=85077979067&partnerID=8YFLogxK
U2 - 10.4230/LIPIcs.ITCS.2020.71
DO - 10.4230/LIPIcs.ITCS.2020.71
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AN - SCOPUS:85077979067
T3 - Leibniz International Proceedings in Informatics, LIPIcs
BT - 11th Innovations in Theoretical Computer Science Conference, ITCS 2020
A2 - Vidick, Thomas
T2 - 11th Innovations in Theoretical Computer Science Conference, ITCS 2020
Y2 - 12 January 2020 through 14 January 2020
ER -