Questions tagged [functional-encryption]
Functional encryption is a type of public-key encryption, where the party that has access to a secret key can learn a function from that key, which is used to encrypt and decrypt messages.
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Decryption of LWE-based Inner-Product Fuctional Encryption of Agrawal-Libert-Stehle Crypto 2016
In below image, we have LWE-based inner-product functional encryption for short integers
[ALS'Crypto2016].
Is the encryption correct? Why do they get $\mu\in\{\color{red}{-K+1},\ldots,0,K+1\}$? When ...
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Zero-Knowledge Proof of a number being generated "randomly" (similar to a dice roll)
If party1 asks other parties to give a random number, for simplicity, say in a range from 1 to 6 (like in a dice). Is it possible for party1 to ensure that the number received is in a given range and ...
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How to determine approximate factor (i.e. modulus-to-(bound of)noise ratio) of LWE in advaned primitives is sub-exponential or polynomial?
In advanced primitives like circuit (policy) ABE [BGG+'Eurocrypt2014] or IPFE [ACGU'Asiacrypt2020, appedix A] based on lattices, parameters setting is quite puzzling and vague (for me).
(Parameter ...
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Does the following variant of functional encryption exist?
For a (possibly complicated) function $f: X \rightarrow Y$, can we design a set of encryption scheme $Enc, Func\_Enc$ such that, for $\forall x \in X$,
$$Func\_Enc(f) = g \text{ where } g \text{ is ...
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Which one is more general, attribute based encryption or inner product predicate encryption?
If we have a scheme for inner product predicate encryption (IPPE), then can we claim that we already have designed an attribute based encryption (ABE) scheme; So we do not need to design an ABE again. ...
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Functional Encryption in Private-key setting vs. Public-key setting
$\bullet$ What does private-key functional encryption mean? Or functional encryption in private-key setting?
Wasn't functional encryption a generalization of public key encryption? So now, why do we ...
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On the spectral norm in lattice-based cryptography
In the preliminaries section of a paper$^\color{magenta}{\star}$ on lattice-based cryptography, the matrix norm $\| \cdot \|_{2}$ is used. Why do we define such norm? What's the purpose of defining ...
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Is it possible to design an algorithm that is based on the xor of the plaintext bits?
Let E be some IND-CPA public key encryption scheme. Given two users with public keys $pk_0,pk_1$ respectively, each user $i$ selects a nonce $r_i$ at random and computes an encryption $c_i = E_{pk_i,...
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Is Order-preserving encryption part of the functional encryption family?
I believe I know quite well OPE and ORE, but I'm unsure about what family to put them in. Can we consider them as a sub family of Functional Encryption, like Attribute Based Encryption or Inner ...
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Can functional encryption encrypt and decrypt negative integers?
I want to use DCR-based functional encryption for encryption and decryption purpose. However, I'm unsure whether DCR-based functional encryption can support negative integers.
Is there any ...
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Secuirty definion of a ad hoc multi-input functional encryption scheme
I have to write an essay on the paper ad hoc multi-input functional encryption, and can't understand the security definition. In a nutshell it is a primitive that allow sources to supply encrypted ...
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Functional Encrypton: multiplying an encrypted vector by huge known matrix through inner product encrypton?
I'm solving a kernel ridge regression through a federated learning way.
Equation to solve the kernel ridge regerssion is dot((K+lambdaI)^-1,y).
So the aggregator of the problem knows the matrix A=(K+...
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Is it secure if a secret key is used in the function of a functional encryption?
In my scheme, two functional encryptions FE1 and FE2 are used. The function f1 corresponding to FE1 is as follows:
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How to prove the security if a circuit is obscured by an IO，where the key generattion algorithm of a functional encryption is used in the circuit?
I want to design a scheme, where there is a circuit C0 which is obscured by an indistinguishability obfuscation (IO). In C0, a master key of a functional encryption (FE) is hardwired. Given an input z ...
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Is there a function-hiding functional encryption for quadratic polynomials?
Recently, I have found research papers about the functional encryptions for inner products and quadratic polynomials.
For inner products, there are a few papers which focus to construct efficient ...
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Indistinguishable Obfuscation vs Functional Encryption
What is the difference between Functional Encryption from Indistinguishable Obfuscation? Is one of them having more stronger security than the other?
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Do I understand $P = NP$ correctly in relation to one-way functions?
If I understand this relation correctly is, that any function whose inverse can be found in polynomial time is not a one way function. The $P = NP$ proved would cause that any candidate for a one-way ...
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functional encryption over homomorphic encryption
I recently read about "functional encryption" which seems interesting, although I didn't understand yet how it works ... but is it possible to combine it or adapt it with homomorphic ...
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What is the size of a 1024-bit RSA cipher compared to its plaintext?
Let's assume we encrypt a 50000 bit plaintext with 1024-bit RSA and public exponent $e$ = 3: How big will its cipher be?
When we increase the exponent to let's say $e$ = 216 + 1 = 65537, how big will ...
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Safety of a private key when knowing the full content of an encrypted message in case of fixed initialization vector
When knowing the full content of the original message, will I be able to derive the private key from the encrypted message when the underlying encryption uses a fixed initialization vector?
Meaning if ...
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What is the current state-of-the-art of function-private functional encryption?
Are there any known constructions of functional encryption with function-privacy for arbitrary functions (e.g. not just inner-product)? If so, are these constructions currently feasible or for now ...
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Pairing-free group based encryption scheme
Can someone explain what is a pairing-free group ? There is encryption schemes, for example 1, that qualify there proposed construction as pairing-free group. However, they use bilinear group in the ...
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Hardwired secret key in public / private key encryption
I am new to cryptography and I need to know some details about the hardwired keys.
Taking as an example the paper "Multi-Input Functional Encryption", a key is hardwired in the description of the ...
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Homomorphic & Functional encryption: Mapping unencrypted outputs to encrypted outputs using existing data
Let's assume I have datapiece A which, after being put through a model or neural network, has a known output X in the unencrypted space. When I move datapiece A into an encrypted space, and put it ...
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Functional encryption for inner products from DDH
I have been reading this paper by Abdalla, et al. But there's something I don't get about the security proof (Theorem 3.2) for the basic IP scheme from DDH--how are they simulating the mpk's using $g^...
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Is there any kind of function that has a property like this?
First of all, sorry for any horrible formatting, I have to type this in from my phone.
I know (or, at least, I think) that no currently used cryptographically secure hash functions exist with this ...
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derive child keys from a private key
My problem is the following:
I have an organization with many members. When someone from the outside communicates with this organization, I want any member to be able to decrypt the communication.
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Correctness and how to define it using probability
I would like to understand why some definitions of correctness allow a negligible failure probability. i.e. the probability that decryption reverses encryption is 1 minus a negligibly small amount.
I ...
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Enabling Oblivious Access Control via Function Encryption
Abstract
With Functional Encryption, would access control between two parties be possible without revealing the entirety of one party's policy to the other? E.g. such that a server would be incapable ...
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Functional signatures with ECDSA Verifier
Functional signatures use some master key to create a functional signature key. The functional key can be used to sign messages, but only if the message is accepted by some predicate function. For ...
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How to encrypt a message such when a certain condition is met it can be decrypted?
Assume, there is a certificate authority whose public key: $pk$, is known. Also, the certificate $c$ is known, but not the signed certificate.
I want to encrypt a message: $m$, such that whoever has a ...
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Special-purpose witness encryption without multilinear maps
In Witness Encryption and its Applications Garg et al describe "witness encryption" which allows one to encrypt some specified data to a NP problem, such that another party can decrypt iff they ...
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What is Indistinguishability Obfuscation?
I've been studying functional encryption. I recently read that a multi-input functional encryption (MIFE) implies indistinguishability obfuscation (IO).
Can someone please brief me: what is ...
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Indistinguishability Obfuscation : What are it's consequences on crypto? [closed]
I was reading about the construction of IO using MIFE and compact FE . I am just curious to know what are the consequences if there exists an IO.
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What is complexity leveraging
Complexity leveraging is a technique that is generally used to prove adaptive security of a selectively secure scheme. Eg: We can prove adaptive security of Yao's garbling scheme using complexity ...
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Weakly Sublinear Compact FE from Succinct FE and XiO
I'm confused about a problem these days and I decided to seek an answer here. The question is about the section 4.1 of the paper LPST16. Let me recall the weakly sublinear compact FE scheme $\textrm{...
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Is there any functional encryption scheme whose key generation circuit is in NC1?
To my best of knowledge, I have kown there exists randomized encoding scheme whose encoding circuit is in $NC^1$, fully homomorphic encryption scheme whose decryption circuit is in $NC^1$, and ...
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Is a good idea to generate a public key from a secret key using a functional encryption scheme?
FE - functional encryption
PK - public key
I want to design a PK cryptosystem that has a unique PK for each encryptor. Namely, the encryptor submits a unique value (or an attribute) to the private ...
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What functional encryption scheme can be used to compute a linear function?
I am looking for a functional encryption scheme that can compute a linear function. I do not need to work with attributes.
All I want is to compute the result of a function $y = a*x+b$, where $x$ is ...
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How does ABE decryption works? [duplicate]
I am trying to understand how Attribute Base Encryption (ABE) works. So, after downloading libfenc library from here, I built the source code on Ubuntu 12.04 without any error. Afterward, I tried to ...
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What is matrix branching program?
Recently I am reading something about order-revealing encryption (by Boneh at al. in EuroCrypt 2015) and encountered "matrix branching programming". It seems like it took me forever to understand this....
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Simple example to describe Bilinear mapping
Notation : $\mathbb{G}$ is an additive group and $\mathbb{G}_T$ is multiplicative group of prime order $q$.
Bilinear mapping $e: \mathbb{G} \times \mathbb{G} \rightarrow \mathbb{G}_T$ has to satisfy ...
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What are the current limitations (and capabilities) of Functional Encryption used for access control?
I'm trying to make my way in Functional Encryption used for access control.
I read a lot of papers such as "How to Run Turing Machines on Encrypted Data", "Functional Encryption: New Perspectives and ...
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fully homomorphic encryption (FHE)
Please, I would like to find some hints or solution to my following problem, I would appreciate your assistance to walk with me throughout the solution
Given fully homomorphic encryption (FHE) ...
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Can we run a probabilistic function on ciphertext with Functional Encryption (or Attribute Based Encryption)?
In the definition of functional encryption ($FE$):
$FE.Setup(1^k)$ takes as input the security parameter $1^k$ and outputs a master public key $fmpk$ and a master secret key $fmsk$.
$FE.KeyGen(fmsk, ...
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"Practical" operations supported by functional encryption?
I'm curious about what operations have been developed into functional encryption schemes.
What I mean by that is: what operations can be performed over encrypted ciphertexts? Obviously homomorphic ...
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Functional Encryption (for Non Experts)
I recently stumbled across "How to Run Turing Machines on Encrypted Data".
Given that it's now possible to run turing machines on encrypted data, what open problems remain in the realm of Functional ...
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Are there any Truth Table to Boolean expression converters? [closed]
I am working on Bent functions that are of interest in cryptography. I developed an algorithm that construct such functions. However, I need some tools to calculate boolean expression from the truth ...
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Practical consequences of using functional encryption for software obfuscation
I came across this article, which describes a method, developed by UCLA CS professor Amit Sahai et al, for using functional encryption in order to achieve software obfuscation. The paper that the ...
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Is Functional Encryption about Access Control over encrypted data alone?
Informally, In functional encryption system , a decryption key allows a user to
learn a function of the encrypted data. But all i see is that the function acts as an access control over the data.
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