Questions tagged [data-privacy]

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

Filter by
Sorted by
Tagged with
1 vote
0 answers
30 views

Information-theoretically secure computation of a conjunction (with a semi-honest third party)

Suppose Alice and Bob want to compute the conjunction of their private bits in an information-theoretically secure way (so this approach, which uses standard oblivious transfer, does not suffice). ...
user avatar
  • 199
3 votes
3 answers
122 views

Public-key/asymmetric encryption where you can only leak the decrypted message by leaking your password

A bunch of friends are using public-key encryption to send encrypted messages to each other using an open public forum. I.e. each friend has a public key (which you can use to encrypt messages for ...
user avatar
  • 335
0 votes
1 answer
87 views

Best way to encrypt sensitive data on server with HSM and symmetric keys

I need to store sensitive data (like customer photos) in a SQL database in the most secure way in case of security breaches. The data won't be accessed by the clients, only to internal processes that ...
user avatar
  • 1
0 votes
1 answer
34 views

When can composition be viewed as a vector-valued query with differential privacy?

Page 33 of The Algorithmic Foundations of Differential Privacy gives two examples where a composition of mechanisms can be viewed as a vector-values output, histograms, and fixed counting queries, ...
user avatar
0 votes
0 answers
40 views

Compute Differential Privacy level for any randomised algorithm

I have recently started learning differential privacy for my BTech project. I understand that it adds noise to the input stream based on a privacy level (say $\epsilon$) and a query function (say $f$),...
user avatar
2 votes
1 answer
87 views

If the symmetric key is stolen; can I key revoke without reencrypted data?

I have a question about database security. This is a scenario I have. The data is encrypted using symmetric (i.e., AES) and stored in a database, while the secret key is stored on the client side, so ...
user avatar
  • 21
1 vote
1 answer
52 views

Securely sort lists of numbers from two parties

I am looking for ways to securely sort two lists of numbers. Yao's millionaire's problem considers each party with one secrete number and compare them securely. Are there papers on extension to this ...
user avatar
1 vote
1 answer
54 views

Advanced Composition in DP is worse than Basic Composition

I have problems with understanding the advanced composition theorem in DP. Let I have two approximate-DP mechanisms ($k = 2)$ where each satisfies $(\epsilon = 0.5, \delta = 0.1)$-DP. By basic ...
user avatar
3 votes
1 answer
77 views

How do we select values for parameters when using Differential Privacy?

I'm aware we can quantify privacy with ε-differential privacy (ε-DP). But when we apply DP, how do we actually select the value for ε ? Are there some rule-of-thumbs? Is it decided case-by-case basis? ...
user avatar
5 votes
1 answer
121 views

What is the best way to pseudonymise IP addresses while retaining the ability to identify those that share a subnet?

Background: I'm developing an app that is based around registered users voting on stuff, and I want to create a heuristic that involves IP addresses as one way to flag accounts for further ...
user avatar
  • 161
2 votes
0 answers
28 views

What is the link between anonymous credentials and transactional pseudonyms?

Anonymous credentials are used to prove certain properties of a specific user without revealing any other information, and transactional pseudonyms are used to authenticate a user as the rightful ...
user avatar
3 votes
2 answers
91 views

Prove that $x$ is the sum of digitally signed numbers without revealing the summands

Imagine this: Charlie chooses two integers $x_1$ and $x_2$ and signs each of these integers with the same private key. Charlie sends the following to Alice: $x_1$ and $x_2$, the two signatures, and ...
user avatar
1 vote
0 answers
25 views

Looking for a (partly) anonymous signature

I am looking a way to sign a document, so that everyone could verify that one person out of a group did, but only a special person and/or the group could know who signed it. Let's say, X chooses a ...
user avatar
  • 469
1 vote
1 answer
135 views

Differential Privacy: Gaussian Mechanism when $\epsilon >1$, Laplace Mechanism when $\epsilon = 0$

In Differential Privacy resources, the limiting cases of $\epsilon, \delta$ are not justified well enough. For example, on Wikipedia, it is said that Gaussian mechanism only works when $\epsilon < ...
user avatar
0 votes
0 answers
43 views

Revealing percentiles of an ordered dataset without revealing its size

Given an ordered set $S$ of positive integers (eg. $S=\{503, 503, 520, 551...N\}$) I want to be able to reveal the percentile rank (eg. 503 is in the top 10th percentile) for each element of a ...
user avatar
  • 101
0 votes
0 answers
23 views

Linking attacks on anonymized data

I'm working on a anonymization project and I got interested in linking attacks. For simplicity I only look at data in table format, such as xlxx or csv data. To anonymise such data the most common ...
user avatar
  • 1,492
0 votes
0 answers
39 views

Is it possible to allow a user to log in if logged out without identifying them?

I have to verify that the user has registered and is currently logged out without identifying the user. Essentially, I am looking for privacy-oriented authorization mechanisms which prevent ...
user avatar
  • 101
1 vote
1 answer
21 views

Sensitivy Maximization RAPPOR (Local Differential Privacy)

Hi I have a doubt at the end of the proof of the RAPPOR Algorithm, when they say the sensitivity is maximized when $b'_{h+1}=b'_{h+2}=...=b'_{2h}=1$ and $b'_{1}=b'_{2}=...=b'_{h}=0$. I don't ...
user avatar
2 votes
1 answer
86 views

Data Security and Encryption

I have a research paper on data security using proxy re-encryption, and I need to provide an answer to a reviewer's comment. However, I have no idea on what to do or how to answer it. The security ...
user avatar
  • 21
2 votes
2 answers
49 views

What is $z_b$ in this introduction to Private Information Retrieval?

I was trying to read this introduction to private information retrieval. On page 12 of the document, a scheme for 1-DB private information retrieval is discussed. I was unable to understand one of the ...
user avatar
2 votes
1 answer
74 views

How to adapt the equation of Gaussian mechanism noise based on number of executions

I'm trying to build a differentially private machine learning model. I'm using the Gaussian mechanism to calculate the required noise amount based on pre-defined privacy budget value 𝜖 The equation ...
user avatar
  • 23
0 votes
0 answers
40 views

Mechanisms for masking identifying unique IDs with non-identifying unique IDs to protect privacy?

I need to suggest mechanisms for masking unique codes in a database with different unique codes that are not derived from the original unique codes, but are equivalently unique in that they could ...
user avatar
1 vote
1 answer
118 views

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 ...
user avatar
  • 235
1 vote
2 answers
205 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 ...
user avatar
  • 978
0 votes
0 answers
18 views

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. ...
user avatar
  • 111
2 votes
1 answer
59 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 $...
user avatar
  • 21
3 votes
1 answer
102 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 ...
user avatar
2 votes
1 answer
415 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 ...
user avatar
1 vote
1 answer
216 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 $(\varepsilon,\delta)$-...
user avatar
2 votes
0 answers
81 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 ...
user avatar
3 votes
1 answer
153 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,...
user avatar
1 vote
0 answers
66 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'...
user avatar
  • 43
2 votes
1 answer
187 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 ...
user avatar
2 votes
1 answer
151 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 '...
user avatar
0 votes
1 answer
388 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 ...
user avatar
2 votes
1 answer
118 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 ...
user avatar
  • 361
0 votes
2 answers
135 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 $\...
user avatar
  • 101
1 vote
1 answer
76 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 ...
user avatar
  • 675
0 votes
0 answers
156 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,...
user avatar
  • 101
0 votes
1 answer
162 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 ...
user avatar
0 votes
0 answers
48 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 ...
user avatar
1 vote
0 answers
57 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, ...
user avatar
0 votes
2 answers
57 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 ...
user avatar
  • 83
3 votes
2 answers
932 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 ...
user avatar
1 vote
0 answers
82 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 ...
user avatar
  • 155
3 votes
2 answers
122 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 ...
user avatar
  • 133
2 votes
0 answers
63 views

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 \\...
user avatar
0 votes
0 answers
48 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 ...
user avatar
  • 1
3 votes
1 answer
128 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 ...
user avatar
1 vote
1 answer
71 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 ...
user avatar
  • 111