Questions tagged [data-privacy]

Data privacy refers to (cryptographic) methods to prevent the disclosure of sensitive (identifying) information of persons.

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Differential privacy what does “where the probability is taken over the randomness used by the algorithm” mean?

The definition of differential privacy is as follows: A randomized mechanism $\mathcal{M}$ is $(\epsilon, \delta)$-differentially private, where $\epsilon \leq 0$ and $\delta \leq 0$, if for any ...
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141 views

Differential privacy noise that scales with $L_p$-sensitivity with $p>2$?

It is well-known that to make the result of a $\mathbb{R}^d$-valued query $(\varepsilon,\delta)$-differentially private, you can add noise to it. If you add Laplace noise, you need to scale the noise ...
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Check correctness of data using only publicly known variables and a server response

A smart contract (a publicly known program) needs to check if the data D is correct (belongs to some fixed set). It is by definition correct if our trusted server checks it and decides it's correct. ...
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35 views

The sensitivity in differential privacy with deep learning

In differentially private deep learning, the sensitivity is determined by clipping gradient norm (see Abadi et al.'s paper). In this paper, when the clipping gradient norm is $C$, the sensitivity is $...
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75 views

Laplace Inequality

I am trying to prove that if $r_i \sim Lap(0,1/\varepsilon)$ where $\varepsilon >0$ then: $$Pr[r_i \geq 1+r^*] \geq e^{-\varepsilon}Pr[r_i \geq r^{*}]$$. I know that for $r*>0$ it satisfies ...
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73 views

$(\epsilon, \delta)$-differential privacy: main motivation of $\delta$

I am wondering why (not how) we relax $\epsilon$-differential privacy to $(\epsilon, \delta)$-differential privacy. Is the main motivation to reduce the variance of the noise added to the query with a ...
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60 views

Advanced Composition (Differential Privacy)

I have a problem understanding the proof of the corollary of Advanced Composition Theorem Advanced Composition: For all $\varepsilon,\delta,\delta' \geq 0$ the class of $(\varepsilon,\delta)$-...
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48 views

Content Key Encryption for Multi-User data access

I recently worked out a concept for a use-case, but I'm not sure if my approach is good enough. So I would appreciate feedback and things to look out for, as I'm fairly new to this field. A User can ...
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1answer
45 views

Lemma KL-Divergence (Differential Privacy)

I am studying differential privacy and I got stuck again in proof of a lemma. Which is: $D_{\infty}^\delta(Y||Z) \leq \epsilon$ if and only if there exists a random variable $Y'$ such that $\Delta(Y,...
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41 views

Is using Fiat-shamir Heuristic safe?

What I'd like to do is to have the Prover store a value x where x remains hidden. From x, I'...
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41 views

Calculating the privacy that Renyi ($\epsilon, \delta$) Differential Privacy satisfies

I add differential privacy (DP) to my machine learning models by using PyTorch-DP. PyTorch-DP supplies me with the values: $\epsilon$ and $\delta $. I know that the $\epsilon$ tells us something about ...
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1answer
94 views

Differential Privacy: What is the 'game' between data holder and adversary?

I have been reading the Differential Privacy (DP) literature for some time to get familiar with it. I feel comfortable with the Math and Stats foundations of it, but I am suffering a bit from the '...
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70 views

how many iterations of SHA3 (keccak256) hashing would be required to provide reasonable protection for the following data structure?

((A , B , C) , (D , E , F, G, H)) Where: A is 0x0-0xF, (1 of 16) B is 0x00-0xFF (1 of 256) C is an 8 digit integer D is a one of a list of one hundred words padded to 12 characters E is a one ...
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1answer
73 views

Compute euclidian distance on encrypted data

The scenario is described as following: Let $A$ an user that is transmitting an encrypted (with its own public key $PK_A$) data vector containing its position as $p = Enc(PK_A, [x,y])$ towards a group ...
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2answers
68 views

What is the implication for differential privacy if $\epsilon = 0$?

In pure differential privacy, the parameter $\epsilon$ represents the desired privacy loss. The smaller the $\epsilon$ is, the more privacy we can obtain. What happens when we want the privacy loss $\...
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70 views

Which is more secure PEPP-PT or DP-3T?

Which of these population tracking protocols is better from a cryptography point of view? Pan-European Privacy-Preserving Proximity Tracing (PEPP-PT) Decentralized Privacy-Preserving Proximity ...
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56 views

Encrypting conversation messages stored in database (symmetric encryption)

I have a chatting application like Slack/Discord. In this chat application there chat groups and messages sent by users need to be encrypted in the database. I do not need features like E2E encryption,...
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59 views

Adding the same noise to all element of a vector is Differential privacy

In Differential privacy, if we add a $N$-dimension private vector with $N$-dimension Laplace or Gauss noise, we obtain differential privacy. However, if we only generate a 1-dimension noise to add it ...
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38 views

Proving anonymous credential presentation

In a CL-based or CKS-based anonymous credential system, how can a verifier $V$ prove that a credential holder $H$ has presented it a credential that has been issued by an issuer $I$ without ...
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52 views

Comparison of end-to-end encryption and TLS

I am writing a comparison paper about security of electronic communication and I want to compare end-to-end encryption and TLS by giving two examples such as Whatsapp and Facebook Messenger. However, ...
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2answers
50 views

privacy enhancing techniques on image data

To give some context: I am looking for a suite of techniques and tools that can theoretically enable me to conduct analysis such as classification on image datasets in a manner in which a naive ...
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386 views

Interpretation of advanced composition theorem of differential privacy

In "The Algorithmic Foundations of Differential Privacy" book, Advanced Decomposition Theorem (Thm 3.20) is stated as follows: For all "$\epsilon, \delta, \delta' \geq 0$, the class of ...
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64 views

Sigma Protocol with Privacy-preserving Discrete Logarithms?

I've been reading up on Sigma Protocols and Fiat-Shamir Heuristic. There is a small problem I see here that is possibly already solved, but I'd like to know if it has a solution. Peggy wants to prove ...
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2answers
86 views

What's the meaning of probabilities in differential privacy formula?

I don't understand what does it mean by "The probability is taken is over the coin tosses of K." Does it mean, the probability distribution is generated based on exactly same data but only the ...
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Differential privacy RAPPOR article proof doubts

Recently I've been trying to understand the RAPPOR proof: \begin{eqnarray*} P(B' = b' | B = b^*) & = & \left(\frac{1}{2}f\right)^{b'_1}\left(1 - \frac{1}{2}f\right)^{1 - b'_1} \times \ldots \\...
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42 views

Two parties looking to share data anonymously

I've been struggling to find good info on how to do the following: A(lice) and B(ob) each have a table of data (a and b ...
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101 views

Why does ε-differential privacy protect the subset of 1/ε edges in terms of graphs?

In the book The Algorithmic Foundations of Differential Privacy by Cynthia Dwork, Aaron Roth on page 24, databases that take the form of graphs are discussed. We could on the other hand consider ...
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1answer
62 views

Facebook app-scoped identifiers and similar - implementing stateless ID obfuscation

After certain privacy concerns Facebook rolled out a bunch of changes to their APIs, one being "scoping" user identifiers per app. In effect, this means that Alice's canonical facebook user ID is ...
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Pros/cons of anonymity when messages are encrypted? [closed]

Let's say I'm making an end-to-end encrypted messaging app with the goal of putting "privacy first." The contents of messages are encrypted, but in the current model, it is still visible to the server ...
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996 views

Why the definition in $\epsilon$-differential privacy is multiplicative rather than additive?

According to its mathematical definition, a random algorithm $M: D\rightarrow R$ satisfies $\epsilon$-differential privacy if the adjacent datasets $x, y \in D$ where $D$ is a whole dataset and ...
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41 views

Audio Files and Digital Bearer Instruments

Is it possible to combine Audio Files and Public Key Cryptography creating a Digital Bearer Audio File that is in complete control of the owner who would then have the ability to grant access to ...
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105 views

Private Set Intersection using a subset of the larger set

Alice has a set $S_A$ with a low cardinality (say ~30k). Bob on the other hand has a set $S_B$ with a much higher cardinality than of Alice's (say ~100M). We're trying to create a reduced ...
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77 views

Data masking / Data obfuscation for string int float and date , preserving order and exact matches

I've to mask data into some different value but to keep their property such as order an exact match (substring is yet impossible) What's the state of the art in data masking? I've some data on which ...
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2answers
696 views

Are there any practical use cases for performing homomorphic operations on encrypted Strings?

Does anybody know which practical use cases there are to operate on encrypted strings? Even niche problems that can be solved using homomorphic encryption on strings are interesting to me, but not ...
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1answer
172 views

What are the advantages of mutual private set intersection methods over finding the intersection of hashed lists?

I can understand the usefulness of one-way private set intersection methods. Where Alice and Bob both have listed but only Alice learns the intersection of those lists while Bob learns nothing. I ...
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146 views

How Zero Knowledge Proof enables Privacy By Design [closed]

How does Zero Knowledge Proof (ZKP) enable Privacy By Design?
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Zero knowledge proof in smart parking managment systems

I read this paper on protecting user privacy in smart parking management system. It talks about using zero knowledge proofs to protect privacy but I am not certain how they do it. My assumption is ...
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1answer
266 views

lookup encrypted text by clear text without decryption

I've implemented vouchers module in my web project where I use it to generate redeem get etc... vouchers. since voucher codes are considered sensitive, I've considered to encrypt them using AES-GCM. ...
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152 views

Laplace mechanism from Exponential mechanism in Differential Privacy

In McSherry and Talwar's paper which introduces the exponential mechanism for differential privacy, they say that the Laplace mechanism can be captured by choosing the score function as $q(d,r) = - |f(...
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124 views

Cryptographic scheme where a single message cannot be decrypted but if combined with other it can be

i'm wondering if this type of cryptographic scheme does exists. I know about homomorphic encryption but if one has the private key, he can decrypt every single message. I would like to know if there ...
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1answer
57 views

Filter party-1 strings against party-2 white/black list keeping the lists private

Suppose I have a server and a client. The client has a list of arbitrary strings and the server is supposed to filter this list using white and black lists kept on the server side. It would be nice ...
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95 views

End-To-End encryption for VoIP teleconference applications and many-to-many lag-sensitive applications

There are various protocols that allow you to have privacy-enhanced chat. Those can be either 2-party chat such as: OTR SIGNAL or multiparty chat such as: SIGNAL (n+1)sec mpOTR GOTR (2013 spec and ...
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1answer
44 views

what can attackers do between two end hosts

I have one question that I couldn't come up with a nice solution. So let's have this analogy, I have a box full of money and I want to deliver to this my friend. Here if we think of a potential ...
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1answer
635 views

Difference between ε-differential privacy and (ε, δ)-differential privacy

I don't understand the necessity of introducing the additive term δ in the differential privacy definition. Moreover, reading different papers and blogs they say that because of the δ term the ...
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3answers
244 views

Encryption for IOT devices with minimal overhead

I have several IOT devices that transmits nearly 200 bytes of data every 10 seconds. I want to make the data secured but i also want to keep the data size nearly same. Ofcourse for IOT devices ...
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1answer
96 views

Is it possible to derive the recipient's public key from libsodium's crypto_box?

Libsodium has "crypto_box_seal" which according to the documentation is used to "anonymously send messages to a recipient given its public key.", which hides the sender. But Is it possible for Eve to ...
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107 views

Is this construction a secure MAC?

Let $F:\{ 0,1 \}^n \times \{ 0,1 \}^ n \rightarrow Z^*_q $ is a PRF, and $H:\{ 0,1 \}^{2n} \rightarrow \{ 0,1\}^n$ is a secure hash function. Is the following construction $\Pi=(Gen,Mac,Vrfy)$ is a ...
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0answers
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Avoiding multiple use of sIgned identities while not learning anything about them

There is an authority A with an associated public/private key pair (A.priv, A.pub). A can issue new "identities" by signing data (numbers or bytestrings). Each number associated with a signature by A ...
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1answer
34 views

Divide data into parts and restore from them

I'm not much familiar with cryptography, so please guide me in the right direction on the following question: Let's say I have some data (array of bytes) $D$. I want to convert it into $N$ pieces (...
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145 views

Leak information (new setting)

This question is similar to Leak Information?, but with new settings. Let $a,b,c,d,e,f$ be selected at random from $\mathbb Z^*_q$. Also, let $r_1,r_2,r_3,z_1,z_2,z_3,p_1,p_2,p_3$ be selected at ...