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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What is an example of a secure sigma proof?

I want to implement Threshold Elgamal as described in section 6.3.1 and in the decryption phase each party must broadcast a sigma proof to show that it actually has a valid secret share of the secret ...
4
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30 views

An MPC protocol from Elgamal is a good solution a homomorphic multiplication?

I want to compute a multiplication between many secret values and then distribute the result to everyone involved. For this, I thought about an MPC protocol built from Threshold Homomorphic Elgamal. ...
4
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61 views

How can I implement decryption for NTRU homomorphic encryption scheme?

I have come across this paper On-the-fly multiparty computation via on-the-cloud Multikey from Fully Homomorphic Encryption by Lopez-Alt et al., where authors describe a NTRU-based homomorphic ...
2
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1answer
41 views

How to test an implementation of a homomorphic scheme?

I want to implement the following homomorphic encryption scheme from On-the-Fly Multiparty Computation on the Cloud via Multikey Fully Homomorphic Encryption by Lopez-Alt et al. I use C++ and I want ...
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1answer
32 views

Multi Party System with n-1 adversaries

Novice here. Is there a MPC function where no information is leaked even if all parties are not trustworthy ?
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1answer
23 views

Secure Multiparty Computation with Secret Output

Is there any MPC scheme that allows a function with several secret inputs to be computed, while the output can only become known to one specific party? If not, is this even possible?
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82 views

What type of encryption scheme can prevent cheating in this coin flip protocol? [duplicate]

Consider the following protocol for two parties to flip a fair coin: Trusted party $T$ publishes her public key $p_k$ A chooses a random bit $b_A$, encrypts it under $p_k$, and announces the ...
3
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1answer
52 views

Multi-Party Encryption for a Shared Document

Is there an encryption algorithm/protocol where any of a pre-defined set of keys/passwords will succeed in decrypting a document? The number of keys can be fixed, say, 10 or 20 possible passwords. ...
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51 views

How about a homomorphic integer sorting in a MPC context?

I want to implement the ATV-FHE scheme as described by Adriana López-Alt, Eran Tromer, Vinod Vaikuntanathan: On-the-Fly Multiparty Computation on the Cloud via Multikey Fully Homomorphic Encryption ...
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33 views

Are there any FHE-MPC schemes implemented?

I want to know if there are any publicly available multiparty computation schemes derived from fully homomorphic encryption schemes. An example would be the implementation of this scheme ...
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20 views

Proving for a single input vs several inputs. Is there any difference?

I am working on a new protocol for pattern matching. While defining the ideal functionality, it is possible to say: Alice sends $p$ and Bob sends $T$ to the ideal functionality. i.e. searching for ...
5
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2answers
77 views

How many polynomials are used in Secure Multiparty Computation?

Secure Multiparty Computation based on Samir Secret sharing methods rely on Polynomials. Imagine corpus of data should be outsourced to bunch of untrusted servers for any computations. Now the data ...
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51 views

Can several run of a semi-honest protocol be used to infer malicious security?

In the ideal world, $A$ sends several inputs $x_1,...,x_\lambda$ to the functionality and $B$ sends input $y$. Functionality sends $f(x_1,y),...,f(x_\lambda,y)$ to $A$ and nothing to $B$. Suppose ...
2
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1answer
77 views

What is the difference between “securely realizes” and “securely implements”?

In some security proofs it is stated that "a protocol securely realizes an ideal functionality" while in some others "a protocol securely implements an ideal functionality". Is there a meaningful ...
5
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1answer
53 views

Is it possible for a simulator to always abort?

In this paper of J. Baron, et al. (PDF), simulator always aborts the ideal functionality before client outputs its pattern-matching result obtained from the ideal functionality. (See bottom of page ...
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1answer
59 views

Forcing participants to be honest in Secure Multiparty Communication

Alice and Bob engage to compute a secure function f(a,b) where a and b must be present in a ...
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1answer
33 views

how does the simulator work when the corrupted party has no input?

"the only thing the simulator can do in the ideal model is to choose the corrupted parties' inputs." Yehuda Lindell said. 1- what will happen when the corrupted parties have no inputs to the ...
2
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2answers
73 views

regular expression matching on encrypted data using secure multiparty computation

Lets consider Secure Multiparty Computation based on Secret Sharing schemes (rather than Garbled Circuits approach). If we have to do regular expression matching on secret shares of words of texts. ...
5
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1answer
71 views

Designing Secure Multi-Party Computation Sub-Protocols Based on Homomorphic Encryption

When designing SMPC protocols using secret-sharing, it is a common approach to compose a protocol from several sub-protocols (each proven secure under the formal definition of security w.r.t. ...
2
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1answer
34 views

Leakage in Secure Two party Computation

Am trying to understand Garbled Circuit based approach for Secure Two party Computation. There isn't much leakage in the classic millionaire's problem where the comparison circuit is used. But ...
17
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1answer
150 views

What are the roles of the simulator in simulation based proofs

I'm trying to better understand simulation based proofs in the UC model - but the guidelines to construct a simulator confuse me. To my understanding, the simulator is activated in two ways: ...
2
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1answer
128 views

Simulation Based Proof: How the Corrupted Party's Input is Given To Simulator

Imagine we have a 3-party protocol, including client $A$,client $B$ and a server. In this protocol client $B$ encrypts its input under its public key and sends it to the server. The server performs ...
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1answer
180 views

Simulation Based Proof: What Can / Can not Simulator Do?

I have seen some examples in "Foundation of cryptography" and "Efficient two party computation", in which simulator can do some things that in the real world model the parties cannot do, for instance: ...
2
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2answers
51 views

Simulator in Private Outsourced Computation over Outsourced Datasets

Please, consider two honest parties $A$ and $B$ outsourced their private data to a malicious server $S$. So the parties store their data in the server. Then at a later point in time they want to ask ...
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193 views

Simulation based proofs: Simple examples

I am aware that,(in theory) in order to proof that a scheme is secure using simulation based proof we replace an adversary in real world with a simulator in ideal world. Then we try to show that their ...
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2answers
42 views

Correctness of ideal protocol of MPC in presence of malicious adversary

In presence of malicious adversaries in ideal protocol of Multi Party Computation, how can honest parties get the correct output? i.e., corrupted parties modify their inputs and give to the trusted ...
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80 views

secure multi party protocol for multiplication

I started to learn secure multiplication protocol with oblivious transfer. And i came up with this question, Design a secure 2-bit multiplication involving 4 parties? Can any one suggest an answer for ...
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1answer
60 views
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91 views

Correctness in Multi-party Computation: Real/Ideal Paradigm in Malicious case

I need to know: 1- What does exactly correctness mean in this context? 2- How is correctness implied in malicious model? 3- If the correctness means " the adversary cannot cause the output to be ...
2
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2answers
73 views

Are covert and rational adversaries same?

Aumann and Lindell defined covert adversaries in 2009 which is informally adversaries which have a epsilon-deterrence to cheat. Some authors (for ex. John R. Wallrabenstein) have defined similar ...
2
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1answer
131 views

Algorithm for n-of-m keys with partial results

Is there any known and proven algorithm which allows n-of-m keys en/decryption, but doesn't require the keys to be in one location? That is, it allows the plaintext (or ciphertext) to be encrypted (or ...
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1answer
74 views

Malicious party security model: When one party is corrupted at a time

Consider we have three parties,namely client $A$, client $B$ and a server. Client $B$ and the server can be malicious, but we do not allow the adversary to simultaneously corrupt the server and ...
0
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1answer
72 views

Key distribution and computation for homomorphic encryption

How can a system where the party performing a computation also possess the private key and still not know the answer of computation be designed ? Also the other party who does not have the private key ...
2
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1answer
143 views

What's the differences among Blind Computation, Secure Multi-Party Computation, Secure Circuit Evaluation and Homomorphic Encryption

We know that Blind Computation, Secure Multi-Party Computation, Secure Circuit Evaluation and Homomorphic Encryption all can process the encrypted data, but I am puzzled by them. What are their ...
2
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2answers
152 views

What if OT breaks in Yao's garbled circuit?

Two semi-honest parties are computing F with Yao's garbled circuit. Sender garbles it with his inputs baked in then sends it to the receiver. At this point the receiver must use OT to get his keys. ...
5
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1answer
117 views

Secure multiparty computation of conjunction

Suppose Alice and Bob each have bits a and b, respectively. How can Alice and Bob compute the function ...
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184 views

RSA or Paillier is good? [closed]

I want to implement file storage in cloud using homomorphic encryption. I want to use paillier encryption. Can you suggest the drawback of RSA to store and retrieving the files. Then only i can use ...
3
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2answers
268 views

Real life systems that use concepts of crypto computing [closed]

Are there any working cloud/internet solutions/products that operates on encrypted data such as systems using homomorphic encryption, secure multiparty computation, electronic voting, private ...
0
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1answer
187 views

Secure Multiparty Sum in malicious model using threshold encryption

Suppose $n$ actors each hold a plaintext $p_i$. We wish to find $\sum p_i$, without leaking any information about individual $p_i$. Any actor (or any link in the network) could be controlled by an ...
6
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2answers
855 views

What does “circuits” mean in Cryptography?

I am not a hardcore cryptographer so this might be a really stupid question. I am looking through some papers in homomorphic encryption and discovered they describe computation as "circuits", why do ...
3
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1answer
114 views

Why can't garbled circuits be reused?

There are a bunch of papers do research on resizable garbled circuits. But I wonder why garbled circuits cannot be reused? For example, the constructor constructs a garbled circuit of "AND" like ...
2
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1answer
116 views

Implementation of garbled circuits using RSA

I was just reading these notes on garbled (Yao) circuits and I just stuck trying to figure out how an implementation of Table 1 would work using RSA encryption. In RSA the public key is (n,e). So for ...
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68 views

Forward pseudorandom permutation [closed]

Please consider the following scenario: The user A and B use their keys, K1 and K2 respectively. Each client have a vector of elements. Each client separately permutes his vector using his key and ...
2
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1answer
139 views

Secure MultiParty Computation with secret inputs for secret outputs

I want to know if it’s possible to use a SMPC (Secure Multi-Party Computation) to have $N$ entities compute the outcome of a known mathematical operation with two or more secret inputs, where each ...
1
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1answer
57 views

server aid secure equality test

The scenario is like this: $P_1$ has $m_1$, $P_2$ has $m_2$, they want to compare whether $m_1=m_2$ via the server $S$. After the protocol, only $S$ knows the result, and there is no interaction ...
6
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2answers
196 views

Hamiltonicity proof of knowledge

I'm learning the POK notion and definitions and as a self exercise I wante to prove the statement that the Hamiltonicity protocol is a POK system with knowledge error $1/2$. So the question will be ...
2
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1answer
123 views

Computing youngest person among 3 while keeping ages private

I already found a protocol to find out who is richer (older) between two parties, but Is there any protocol to find the youngest person among 3 parties, without revealing actual ages?
3
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1answer
467 views

Can I use Shamir's secret sharing scheme for multiplicative homomorphism for secure multiparty computation?

I would like to perform a dot product operation among $m$ parties using Shamir's $(m,m)$ secret sharing that is used for Secure Multiparty Computation. I am aware that Shamir's $(m,m)$ scheme is ...
3
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2answers
273 views

secure integer comparison

I have been going through a huge amount of papers to find a simple and a practical method to compare integer numbers without revealing their original values. I know that this falls within the area of ...
3
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86 views

Group membership with unique anonymous claims

Is it possible to accomplish the following scheme? There is a Server (S) and many clients. Each client enrolls with S, exposing its real identity; S saves the real identity information in its ...