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Questions tagged [function-evaluation]

Calculating the value of a function for given inputs, especially, in the context of secure multi-party computation and/or homomorphic encryption, without disclosing the inputs to some or all parties carrying out the calculation.

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How can Garbled Circuits be utilized to reduce the round complexity of GMW?

I've been reading this set of notes on some topics in MPC and am having difficulty understanding the transformation the authors make in order to reduce the round complexity of the GMW protocol through ...
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Are there servers that are oblivious to their own output?

Suppose there are $n$ parties with public keys $pk_1,...,pk_n$. Is it possible that a server S constructs an algorithm $A$ so that for some public random nonce $r$ given as input, S computes some &...
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Some questions about the book "Tutorials on the foundations of cryptography: dedicated to Oded Goldreich"

The proof of Theorem 5.2.13 : For semantic security, the author wrote "$m_1 \leftarrow {\rm Sim_1}(1^\lambda)$". I think it may contradict with the security requirement defined in Definition ...
laolien's user avatar
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What security does the BMR protocol offer against corruption?

I've been conducting some research into general-purpose MPC protocols and have been unable to pinpoint the exact security offered by the BMR protocol. The reference I've been using for the majority of ...
YGrade's user avatar
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3 answers
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Earliest citation for truth density

I am searching for a citation of a formula that calculates the proportion of true (1) outcomes in the corresponding truth table of a boolean function. Searching a little bit in the Cryptography ...
John's user avatar
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How to evaluate the security of transposition ciphers?

how to evaluate the security of transposition ciphers? I am specifically interested in the security of turning grilles and how to (mathematically) evaluate their security. I would appreciate any help....
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Difference between function $f$ in eval and dec of homomorphic authenticated encryption

In the homomorphic authenticated encryption, as described 1, there are Eval and Dec PPT algorithms: In Eval, f is the function to be performed on the encrypted data. However, I need to know why it ...
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homomorphic encryption function representation

As it known, Homomorphic encryption can be used for privacy-preserving outsourced storage and computation. In various constructions, the computations are represented as either Boolean or arithmetic ...
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Looking for a formula for "Given $x_1$, $\ldots$, $x_{n-1}$, the output $F(x_1,\ldots,x_n)$ is dependent of $x_n$ and is of $l$-bits security"

Suppose I have a function $F(x_1,\ldots,x_n)$, where each $x_i$ is of $l$-bits security (suppose each $x_i$ is a binary string of length $l$). At the same time, suppose there are $n$ persons, each one ...
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Usage of the nth-root function in cryptography

Having offered a fast integer nth-root algorithm to a bigint library that is also used for cryptography I was asked if it does its work in constant time, so I took a look at the literature to see how ...
deamentiaemundi's user avatar
15 votes
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Representing a function as FHE circuit

I am actually trying to study homomorphic encryption (on lattices) but I'm facing a problem. Every paper that I have read so far talk about writing the function to evaluate on ciphertexts as a circuit,...
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Share Conversion between Different Finite Fields

Let us have any linear secret sharing scheme (LSSS) that works on some field $Z_{p}$, where p is some prime or a power of a prime e.g., Shamir Secret Sharing, Additive secret Sharing. The problem at ...
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SHA-3 Sub-Function Reversibility Clarification

SHA-3 Sub-Function Reversibility Clarification I just finished a very slow and clunky python implementation of SHA-3 (224,256,384,512). The exercise was not designed for speed. My only objective ...
Q-Club's user avatar
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1 answer
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Can big numbers multiplication be a valid form of encryption?

I have a vector of int called $Xreg = [x1, x2, ..., xn]$ that I need to send from a client to a server for storage in a database. If an attacker gains access to the database or the server he shouldn'...
user3336797's user avatar
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SPDZ for the 2-party case

There exist protocols for 2-party computation e.g., GMW that use Boolean circuits. I could also use Paillier and arithmetic circuits for a 2 party computation. However after reading about SPDZ is my ...
DaWNFoRCe's user avatar
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A secure function evaluation problem and an alternative of 1 out of n oblivious transfer?

I am considering a "secure function evaluation" problem: Consider two parties: A and B. A has a one-to-one mapping function $f(x)=k$. Basically, the function $f(x)$ can be regarded as a table of two ...
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Fully Homomorphic Encryption over the Integers - perform an operation on an encrypted data

In Fully Homomorphic Encryption scheme represented here Fully Homomorphic Encryption over the Integers In the Evaluate process (see section “3.1 The Construction” of the paper): $$Evaluate(pk, C, c1, \...
Mohamed Adel Ismail's user avatar
1 vote
1 answer
317 views

Outsourcing arbitrary computations securely

Consider the following scheme. Alice wants Bob to make some computations for her, but she doesn't want to reveal the data on which he's going to do it. So, she encrypts the data, sends them to Bob, he ...
polkovnikov.ph's user avatar
9 votes
3 answers
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How hard is to invert the function that computes the middle-bits of (x^2)?

I'm designing a function f that should be moderately hard to invert and very fast to evaluate in a modern CPU. The function will be used in a proof-of-work function. I've read that the middle-bits of ...
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What criteria make the theta step of Keccak's round function reversible?

From what I've been reading, Keccak's round function is reversible. That's pretty obvious for the $\rho$, $\pi$ and $\iota$ transforms. For $\chi$ to be reversible, $x$'s range has to be odd — but ...
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What's efficient MPC protocol for determining if sum's bigger than y?

My secure multi-party computation (MPC) in need is simply to determine if a sum of two private variable is bigger than a given value $y$, as $f(x_0, x_1) = [(x_0 + x_1) > y]$ in which the value ...
Richard's user avatar
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2 answers
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Alternatives to FHE for secure function evaluation

As a followup to a previous question I asked which was more related to Fully Homomorphic Encryption (FHE), what other cryptographic methods are available for computing a private function on public and/...
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Background for modular arithmetic function

I'm investigating this function: $a := ((b\cdot c) \bmod k) - (b \cdot c)/k$ where $/$ indicates integer division. Two things I've noticed: It's equivalent to multiplying a·b, and then ...
S. Robert James's user avatar
17 votes
2 answers
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Why use a 1-2 Oblivious Transfer instead of a 1 out of n Oblivious Transfer?

When initiating an oblivious transfer, why would someone use a 1-2 oblivious transfer rather than going for an 1 out of n oblivious transfer? Perhaps a slight time overhead for the extra message ...
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