# Questions tagged [data-privacy]

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

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178 views

### computational indistinguishable/distinguishable?

Let $a,b,c,d$ be selected at random from $Z_q$. Consider the following two distributions $X_1$ and $Y_1$: $X_1={(r_1\cdot a, r_2\cdot b, r_3\cdot c, (r_1+r_2-r_3)\cdot d)}$ where $r_1,r_2,r_3$ ...
154 views

### David Chaum's anonymous credential

I am a newbie in cryptography (I know the basic RSA, AES stuffs) and am interested in anonymous authentication systems. Looks like David Chaum is the godly figure in the field. I see lots of people ...
49 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 \\...
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### 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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### 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 ...
177 views

### Merkle tree to prove integrity of subset of data

I'm thinking up a scheme where a merkle tree is used to ensure integrity of a set of data items, and different parties are allowed to verify the integrity of different subsets of that data. Let's ...
88 views

### Sensitivity of probability measure in differential privacy

I know that we need some sort of sensitivity(global, local) to calculate noise that needs to be added for differential privacy. The noise is the maximum difference between two neighboring datasets. ...
272 views

### Evaluate similarity between two “encrypted” time series

Can you think of any way to evaluate the similarity between two time series without revealing any information on the time series ? More precisely, considering two time series $x$ and $y$ of length ...
46 views

### Can I serve data for user without the ability to access them? Which functions for the user remain?

My Problem I want to serve sesible data for users as a webservice that is accessed by the user via the browser. Restrictions: I may not be able to technically acces the data of the user Data is ...
385 views

### CryptDB data re-encryption and onion layers

From the CryptDB paper , I understoond that the onion layers once decrypted are not re-encrypted. Only columns which are queried infrequently will be re-encrypted to higher onion layers. But if we ...
192 views

### Does Ciphertext policy ABE support search operation on encrypted data

Basically CP-ABE (or attribute based encryption) allows end-users to encrypt the data with desired access control structure. I was investigating the how to do keyword-search on encrypted data given ...
23 views

### The sensitivity in differential privacy with deep learning

In differentially private deep learning, the sensitivity is determined by clipping gradient norm(Abadi's paper). In this paper, when the clipping gradient norm is C, the sensitivity is C. Why the ...
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 ...
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'...
39 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 ...
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, ...
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 ...
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 ...
152 views

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### How can user privacy be preserved in certificateless cryptography?

In certificateless cryptography, how can a user preserve his privacy from Key Generation Center? If the KGC becomes malicious, how can the user's privacy be preserved? I read "Privacy-Preserving ...
16 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. ...
58 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 $(\varepsilon,\delta)$-...
69 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 ...
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,...
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 ...
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 ...
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 ...
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 ...