The following statements seems to be a consensus in cryptography community.

Oblivious tranfer is a complete primitive for secure multiparty computation (SMC).

But I cannot find any explicit construction. What I want is a general method to construct SMC from OT with as few assumptions as possible, especially without the computational assumption so that it applies to information-theoretical security.


1 Answer 1


MPC is considered in many settings and flavors, so for simplicity, let's consider a 2-player, semi-honest MPC over $\mathbb{F}_2$ (the bit field).

Sharing the inputs, opening the output, and evaluating XOR gate should proceed as usual (via simple XOR secret sharing -- no need for OT). Alice and Bob can evaluate an AND gate on secret shared inputs $[x],[y]$ for $x,y\in \mathbb{F}_2$ as follows:

  1. Alice chooses a random bit $b$ and accepts it as its secret share of $[x\cdot y]$
  2. Alice prepares a 1 out of 4 OT protocol where the entry corresponding to $[x]_A[y]_A$ (Alice's secret shares) is set to $b\oplus 1$ and all other entries are set to $b$.
  3. Bob inputs $[x]_B[y]_B$ into the OT protocol and accepts the output of the OT, $c$, as its output bit.

It is easy to see that $b\oplus c = 1 \iff xy =1$

  • $\begingroup$ So the secret sharing works as $[x]_A + [x]_B = x$, and $b,c$ are just the secret shares of $z = x \cdot y$ ?(The plus and multiplication are in $\mathbb{F}_2$) Is this exactly the idea of Yao's garbled circuit protocol? $\endgroup$
    – Jiawei Wu
    Apr 20, 2023 at 5:52
  • $\begingroup$ @JiaweiWu what you say is correct. It is also true that garbled circuits are conceptually similar. Most MPC tricks tend to repeat :) $\endgroup$
    – Mr. Jones
    Apr 20, 2023 at 18:22
  • $\begingroup$ Many thanks for your answer! $\endgroup$
    – Jiawei Wu
    Apr 21, 2023 at 7:11

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