Questions tagged [paillier]
A public-key cryptosystem invented by Pascal Paillier in 1999.
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homomorphic division with scaling/Paillier
Let's say that I have to use fractions instead of integers and I am using Paillier cryptosystem. So, I use scaling to obtain integers. Assume that I have a secure division protocol. What happens if ...
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Is it possible to randomize the secret in homomorphic secret sharing?
I was reading the Homomorphic Secret Sharing from Paillier Encryption paper. I see that the authors suggest to secret share $\lambda y$ as $\lambda y = z_1 + z_2$. Then, one can exponentiate an ...
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Pseudorandomness based on homomorphic multiplication property of Paillier cryptosystem
Given the instance $(n, g, \lambda)$ of Paillier cryptosystem with $\text{ord}(g) = n \lambda$ (symbols have their usual meaning), and $c = g^{na}$, is it possible to distinguish (computationally) $c' ...
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How to calculate random factor in Paillier cryptosystem?
I am currently learning paillier cryptosystem,and have two questions about random r.I use the characteristics of homomorphic addition to obtain the product of two ciphertexts C and the corresponding ...
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Homomorphic properties of Paillier
I'm curious about the homomorphic properties of Paillier. So, basically if I have $\textsf{Dec}(\textsf{sk}, \textsf{Enc}(\textsf{pk}, \alpha) \cdot \textsf{Enc}(\textsf{pk}, \alpha^{-1}))$, I will ...
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Prove that some Cyphertext C encrypts some plaintext D
I have a Paillier Cyphertext C and a counterparty that controls the keypair that was used to encrypt the data D to arrive at C.
How can they prove to me that the Cyphertext C is actually the ...
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1answer
69 views
Can the CRT speed-up Paillier decryption by more than a factor of two?
In the Pailler cryptosystem, decryption goes $m\gets\displaystyle\left\lfloor\frac {\left(c^\lambda\bmod n^2\right)-1}n\right\rfloor\mu\bmod n$ with $\mu<n$ being a part of the private key just ...
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44 views
Combining share decryption on Paillier threshold scheme
I am trying to implement the Paillier threshold scheme described by Fouque, et al, but I am having an issue when combining share decryptions.
The scheme calculates the plaintext $M$ with the formula:
...
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1answer
105 views
Applying Chinese RemainderTheorem and Paillier Homomorphic encryption
I'm trying to optimize the decryption process for Paillier Homomorphic Encryption (PHE) using the Chinese Remainder Theorem (CRT). However, I want to check if there's a different way of applying CRT ...
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1answer
48 views
Paillier encryption problem when q or p divides r
I am having a problem with Paillier encryption as described on Wikipedia. It says to pick $0 < r < n$, where $n=pq$ for large, equally sized primes $p$ and $q$. However, I've been testing ...
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Bijective encryption function in Paillier cryptoststem
In Paillier cryptoststem many ciphertexts can correspond to the same plaintext. How can I modify the scheme so to make the correspondence between ciphertexts and plaintexts a one to one correspondece? ...
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In a specific Paillier implementation, why is r prime?
I have a question about an implementation of the Paillier cryptosystem.
In the description of Paillier above, encryption of a plaintext message $m$ on $\mathbb {Z}_{n^{2}}$, $0\leq m<n$, proceeds ...
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1answer
331 views
Paillier: guessing the message when knowing the cipher and the random number
I cannot get my head around this.
In Paillier, the ciphertext is calculated using
$c = g^m.r^n\ mod\ n^2$
where $(n,g)$ forms the public key and $r$ is a random number $0<r<n$.
Assuming an ...
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1answer
52 views
Paillier addition with plain text
$A$ sends $B$ the encryption $E_{pkA}(m)$.
$B$ computes $R=xE_{pkA}(m) + y$ and sends $R$ back to $A$, but tells him nothing about the parameters $x$ and $y$.
$A$ performs $D_{pkA}(R)$ and recovers ...
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1answer
50 views
Verification in Threshold RSA or Threshold Paillier
In the key generation of the threshold version of RSA or the threshold version of the Paillier cryptosystem (e.g. "Shoup - 2000 - Practical threshold signatures" or "Fouque et al. - 2000 - Sharing ...
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The way to calculate $r$ from $c=r^t\mod{n}$ where $(c,t,n)$ is known
I want to know if there is a easy way to calculate $r$ from $c=r^t\mod{n}$ where $(c,t,n)$ is known and $t=pq$ is an RSA?
If $n=t^2$, is it more easier?
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1answer
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Question about Damgård–Jurik crypto system
I am reading the paper about Damgård–Jurik cryptosystem.
In the proof, I found this equation
$c^d = (g^mr^{n^s})^d = (\boxed{(1+n)^{j m}x^m}r^{n^s})^d = \boxed{(1+n)^{j md\pmod{n^s}}}(\boxed{...
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1answer
118 views
Is there any way to prove two numbers that are equal after Paillier encryptions?
I have two numbers $x_1$ and $x_2$, and there are two Paillier homomorphic encryption (public, private) key pairs $(p_1,r_1)$ and $(p_2, r_2)$. I only know $p_1, r_1$ and $p_2$. Suppose $C_1=E_{p_1}(...
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Is it possible to manage an encrypted dataset for face recognition?
Im in my final year of PhD in computer vision and my supervisor has given me a task that I am not very familiar with. So I am teaching myself homomorphic encryption everyday. This question is mostly ...
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122 views
Calculating distance between two vectors using Paillier homomorphic encryption [closed]
I am basically trying to perform euclidean distance calculation in the encrypted domain (Paillier encryption). Using the homomorphic properties of Paillier, the squared euclidean distance formula can ...
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92 views
Paillier's scheme generalisation
Paillier's scheme assume has message and ciphertext space equal to $\mathbb{Z}_N$ with $N=pq$, that is $N$ is the product of two different primes.
Is there a way to generalise this for $N$ that is ...
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1answer
117 views
How to compute Lambda in a Threshold Paillier scheme
I am evaluating a threshold Paillier scheme as described in the paper:
Ivan Damgard, Mads Jurik, Jesper Buus Nielsen, "A Generalization of Paillier’s Public-Key System with Applications to Electronic ...
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1answer
82 views
Paillier subtraction for negative result
I am trying to figure out subtraction on Paillier.
From what I read so far, given $m_1$ smaller than $m_2$ ($m_1<m_2$)
I can compute $E(m_2-m_1)$ as $E(m_2)\cdot E(m_1)^{-1}$ where $E(m_1)^{-1}$ ...
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1answer
51 views
Is Paillier secure from known plaintext attack for single character message?
Assuming I have three messages m1,m2,m3 where m1=m2=m3=1 and I compute c1,c2 and c3.
Does that mean that c1=c2=c3 in cipher-text from ?
If not, how many times can I encrypt a message m=1 and still ...
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1answer
98 views
Paillier Homomoprhic addition overflows after a certain value
I'm new to encryption and am trying to implement Paillier encryption from the wikipedia page here: https://en.wikipedia.org/wiki/Paillier_cryptosystem
I managed to implement the encryption and am ...
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1answer
57 views
I'm getting a non-integer (float) private key in Paillier encryption
I'm trying to implement the Paillier cryptosystem in Matlab using the key generation guidance available here: https://en.wikipedia.org/wiki/Paillier_cryptosystem#Key_generation, but the problem is ...
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Is it possible to re-cipher with Paillier?
I know that with ElGamal we can re-cipher and get a second ciphertext equal to the first.
Is it possible with Paillier too?
When saying "re-cipher", I mean "A sends me a message, that is encrypted ...
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1answer
68 views
algorithmic scheme to compare these two number encrypted using paillier cryptosystem
I have been going through https://eprint.iacr.org/2006/287.pdf (Conjunctive, Subset, and Range Queries on Encrypted Data by Dan boneh)
I am trying to implement the paillier system to create a secure ...
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Theoretical cost of Paillier cryptosystem
How can we estimate the theoretical cost of Paillier cryptosystem?
Examples can be found here https://en.wikipedia.org/wiki/Paillier_cryptosystem ? Can any please discuss the cost in terms of big O ...
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Paillier VS RSA
I was wondering if there are major pros or cons of choosing the Paillier algorithm over RSA except for Pailliers being additively homomorphic and RSA multiplicative?
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1answer
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How do I choose blind sizes?
I am currently developing a service that calculates statistics (currently only sum/average) on homomorphically encrypted user data, and then gives the results to a third party. Because encryption is ...
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1answer
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How to apply two consecutive Paillier encryptions?
The plaintext space for Paillier encryption is $\mathbb{Z}_n$ and the ciphertext space is $\mathbb{Z}_{n^2}$. How can I apply two consecutive encryptions?
I mean, if $c$ is the ciphertext of $m$, how ...
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Division of a number in Paillier encrytion which yields decimal result
I am very new to start with Paillier encryption system. I have used the homomorphic nature of this scheme, which allows addition of two encrypted numbers. I was wondering is it possible to divide two ...
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141 views
Lagrange Gauss Reduction Algorithm
Sorry if my question is trivial. My question is related to a post "Paillier Homomorphic encryption to calculate the means" where a member suggests Lagrange Gauss Reduction Algorithm for reducing a ...
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Zero knowledge proof for Paillier addition under multiple keys
Suppose $m_0, m_1, m_2 \in \mathbb{N}$ such that $m_0 = m_1 + m_2$, $m_i > 0$ (none of them can be 0 or lower)
Under a Paillier cryptosystem, set
$e_0 = E(m_0, r_0)$ for a public key $(g_0, n_0)$
...
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Paillier Homomorphic encryption to calculate the means
Paillier Homomorphic encryption supports addition and multiplication with plaintext value.
Can I use these properties to calculate the means of cipher-text values? I try to use the following steps:
...
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1answer
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In Paillier homomorphic encryption, do we need to take modulo after multiplication of 2 ciphertexts?
The multiplication of 2 ciphertexts generated using Paillier encryption will result in encryption of sum of corresponding plaintexts. I need to do a linear combination operation of N integers in ...
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Taking $p$ and $q$ to be the same value in paillier cryptosystem
I was implementing Paillier cryptosystem when I came across the fact that as soon as I take the primes $p$ = $q$, I start getting incorrect decryption results.
As far as I can understand, when I take $...
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Can McEliece cryptosystem be used as an additively homomorphic encryption scheme?
Since McElice cryptosystem is linear, if matrix G is kept constant for different plaintexts, it can be used for linearly combining the corresponding ciphertexts. In that case, what are the advantages ...
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Viewing elements in $\mathbb Z/n$ as elements in the extension field of $\mathbb{F}_2$
In this article, it is mentioned that in order to use the articles results on field $\mathbb F_2$, one must work on the extension field of $\mathbb F_{2^k}$ (page 6).
That is in order to compute the ...
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2answers
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Does Paillier Homomorphic Encryption Work only with numbers?
Paillier homomorphic encryption enables us to combine two messages such as
$D\left(E(m_1,r_1) \cdot E(m_2,r_2) \mod n^2\right) = m_1+m_2 \mod n$
My question is what are the specification of $m_1$ ...
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1answer
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Paillier paper: Number Theoretic Lemma doesn't seem to work
I'm reading the original Paillier paper.
I've reached Lemma 3: If the order of $g$ is a nonzero multiple of $n$, then $\varepsilon_g(x,y) = g^x y^n \mod n^2$ is a bijection, where $x \in \mathbb{Z}_n$...
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How to prove correct decryption in Paillier cryptosystem
Bob sends a ciphertext obtained by Paillier encryption to Alice.
Alice has the private key. She decrypts the ciphertext and returns the plaintext to Bob.
How can Alice convince Bob that the ...
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1answer
315 views
Zero-Knowledge proof with the paillier cryptosystem
For a paillier cryptosystem how can I perform a zero-knowledge proof?
Given a set of values:
0001
0010
0100
1000
This would be for use in a voting system where we want to ensure we where given a ...
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1answer
378 views
Paillier's Cryptosystem - Secure Key Size
Given Paillier's Cryptosystem. What size in bits would be considered secure for now and the near future? I know it differs for every cryptosystem.
For reference, the most important part of my ...
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1answer
122 views
PHE/FHE add and compare attack
I am aware of this attack that applies to PHE (partially homomorphic encryption) given the attacker has access to a trusted oracle that can Convert (i.e decrypt and ...
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2answers
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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 ...
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Showing the decrypted sum of encrypted values
Is there a system that would allow to encrypt values with one or more keys, sum the encrypted values, and reveal a key which could only decrypt the sum.
Essentially would be able to show encrypted ...
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633 views
Paillier encryption: Many private keys for a public key
Assume $N$ is a public key for paillier encryption, generated by a third party.
Question: Given $N$ can each client generate its own private key, such that its public key is $N$? So all parties ...
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Oblivious Polynomial Evaluation and Encoding Payload
I am trying to parse this paper. I think I do come to understand the general concepts go into this type of Private Set Intersection, based on Oblivious Polynomial Evaluation. I was able to produce a ...
