# Questions tagged [multiparty-computation]

Multi-party computation (MPC) allows a set of parties, each with a private input, to securely and jointly perform any computation over their inputs.

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### BGV KeyGen— Can a maliciously-generated secret-shared key break security (e.g. SPDZ)?

I was (re)reading the paper "Practical Covertly Secure MPC for Dishonest Majority–or: Breaking the SPDZ Limits". One of the key points in this paper is that they present a covertly secure BGV key ...
1answer
287 views

### Security of Fast Two-Party ECDSA Signing

The paper "Fast Secure Two-Party ECDSA Signing" by Yehuda Lindell describes a system in which two parties, $P_1$ (with 1/2 of a share of a long-term ECDSA signing key $x_1$) and $P_2$ (with the other ...
1answer
107 views

### Oblivious transfer with trusted third party Trent

I am trying to solve this exercise. Assume an oblivious transfer protocol that uses a trusted third party Trent. Alice's messages $M_0$ and $M_1$ are binary values of length $k$. Bob's message ...
3answers
150 views

### Algorithm for binary less than in MPC

Given binary shares $[a_{l-1}]_p,...,[a_0]_p, [b_{l-1}]_p,...,[b_0]_p$ such that $a = \sum_{i=0}^{l-1} a_i2^i,b = \sum_{i=0}^{l-1} b_i2^i$ for $a,b \in Z_p$, how to compute $a \overset{?}{\lt} b$ in ...
1answer
151 views

### Interactive Homomorphic Encryption

Let's say that I have a plain computational process that consists of several divisions and I do not want to do it with non-interactive homomorphic encryption. I would like to ask how can I call this ...
1answer
148 views

### Blind Computation

Let's say that there are two parties. Party $A$ has ciphertexts $c_1, c_2$ encrypting data $m_1,m_2$ respectively. $A$ does not know the secret key to decrypt $c_1, c_2$. Party $B$ has the secret key. ...
2answers
301 views

### Algorithm for computing modular inverse in MPC

Is there any known algorithm for calculating $a^{-1} \pmod{q}$, where $q < p$ and $F_{p}$ is the prime field of the MPC, in a linear secret sharing scheme ? I have tried using the standard ...
0answers
83 views

### Distributed generation of random integers with prescribed sum

While reading this document I came across the following problem. Assume you have $n$ clients. The clients need to generate random integers in $\mathbb{Z}_p$, say $T_i$ for $i \in \{1, \ldots, n\}$, ...
2answers
663 views

### Difference between Zero Knowledge Proofs and Multi Party Computation

I am struggling with understanding the difference between the two. From what I am putting together, they have different adversarial models, MPC adds the condition of collusion between parties i.e. ...
1answer
115 views

### What (Where) is the formal definition of Multiparty Computation? [closed]

I'm just curious where we can see a (original) formal definition of MPC. What (Where) is the formal definition of MPC? We have a bunch of tools to build a MPC protocol. Is oblivious transfer (or OT-...
1answer
86 views

### Under what conditions is broadcast possible? (Cryptographically, and in the model of Maurer 2006)

In this paper, Ueli Maurer uses a very cool model to generalize a number of results about broadcast, secret sharing and secure multiparty computation. Rather than talking about an adversary being ...
2answers
310 views

### Multi-secret sharing (Packed secret sharing) - Some questions

In the publication - "Communication complexity of secure computation", I have encountered a small problem - on page 5 of the literature under the heading "Theorem 1" they have ...
1answer
193 views

### Is the simulation-based proof difficult and needed? [closed]

What is the role for simulation-based proof under the semi-honest model without considering malicious adversaries? I agree with that a view of a some party is important to prove that a protocol is ...
1answer
135 views

### MPC on boolean circuits

I am reading about Yao's and GMW protocols and was wondering if there is any perfectly secure MPC protocol in the semi-honest setting, where the underlying circuit is a Boolean circuit (eg. n=3 and t=...
1answer
77 views

### Commitment in two party protocols

I have been reading Fast Secure Two-Party ECDSA Signing by Lindell, and I see that in key generating and signing (pages 9-10, especially visible from Figure 1), only the first party performs a ...
1answer
105 views