Questions tagged [data-privacy]

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

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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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44 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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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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1answer
44 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
47 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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2answers
216 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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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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72 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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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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215 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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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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How Zero Knowledge Proof enables Privacy By Design [closed]

How does Zero Knowledge Proof (ZKP) enable Privacy By Design?
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1answer
96 views

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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117 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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113 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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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
55 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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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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42 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
244 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
191 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
51 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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81 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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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 ...
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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 $r_1,r_2,r_3$ ...
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43 views

Seeking Fast Bloom Filter for Anonymous Address

I had an idea to use something like public message boards to pass secrets anonymously and non-interactively (similar to TV/Movie Trope : http://tvtropes.org/pmwiki/pmwiki.php/Main/PublicSecretMessage )...
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1answer
144 views

Secure distance calculation

I am working on securing a feature in a csv file. My goal is to encrypt, anonymize, mask.... etc the content of the records of the feature while preserving the distance between the characters. as ...
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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 ...
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Any algorithm with a pair of master keys and multiple pairs of subkey for a secure key escrow?

Note: This question looks like my other question — Any algorithm with a master key for decrypting private key encrypted messages? — which is perfectly answered by @real-or-random, but this one is ...
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1answer
702 views

Any algorithm with a master key for decrypting private key encrypted messages?

Are there any algorithm out there that implements following scenario? Create a master private key Create a private/public key #1 based on the master key Create a private/public key #2 based on the ...
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1answer
441 views

Is zero IV with AES-CBC safe if CPA is not possible and indistinguishability is not an issue?

Is using zero IVs with AES-CBC safe, if chosen-plaintext attack (CPA) is not possible and ciphertext indistinguishability is not an issue? Practical example: ...
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1answer
151 views

Understanding the big picture with regard to how anonymous credentials work

I'm trying to learn about anonymous credential systems. I started with Lysyanskaya's thesis, which gives an outline of how to build an AC system given some particular primitives (signature scheme, ...
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Proving to have sent data, without revealing it

This may be easy, but I'm struggling to find a reasonable solution now. Alice wants to send data to Bob. The data that Alice wants to send has been verified by Carl in some way, even though Carl has ...
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1answer
730 views

Is there a hash tree scheme designed for complex data structures?

I have a JSON object with private data. It has the following (complex!) structure: ...
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1answer
146 views

what does differential privacy (in machine learning) promise or guarantee?

I am recently reading some papers about privacy-preserving machine learning. Some works incorporate the idea of differential privacy to protect the privacy of the training dataset when the model is ...
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1answer
110 views

Zero-knowledge voting with hidden weights

Assume a voting with delegates, where each delegate's vote $v_i \in \{-1,1\}$ has a certain weight $w_i$ depending on the number of people who elected the delegate. Is there a way to calculate the ...
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1answer
93 views

Differential privacy on multiple queries – what is the behavior?

Differential privacy framework still continue to be obscure in the following case: If I make a set of queries, I can join their output to restore the original data. For this issue we have composition ...
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2answers
56 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. ...
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1answer
57 views

Increasing Entropy of Limited Information / ID

Supposed that I get an ID from third party (in this case, Telegram ID which is the range $-2^{31}$ to $2^{31}-1$). I want to store the ID securely and privately into my database by hashing it. I don'...
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193 views

Format Preserving Encryption after compression algorithm?

I have large data set which has sensitive information. I want to encrypt different parts of it with different keys. There is also need for compression as data is very large (100s of GB that has to be ...
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1answer
329 views

Comparing two committed values

Given two commitments on different values, Can a third party compare those two commitments to know which one is the higher value?
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347 views

Intuitive explanation of the $\varepsilon$ parameter in differential privacy

I think I have a decent intuitive understanding of what the $\delta$ parameter means in $(\varepsilon,\delta)$-differential privacy: I can explain it to a non-specialist in terms of "what are the ...
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1answer
416 views

Differential Privacy: why $\delta$ negligible on the row numbers?

The definition of differential privacy says that an algorithm $M$ is $(\epsilon,\delta)$-differentially private if $$P(M(x \in D) \in S)\leq e^\epsilon P(M(x \in D')\in S) + \delta$$ where $D,D'$ ...
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1answer
86 views

Disk/File modes of encryption and authentication [closed]

Secure disk/file encryption has been actively studied over the years. Beside XTS and CBC-ESSIV, are there any other modes of encryption that are commonly used? Which could be the most secure mode? ...
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817 views

Integrity with anti-confidentiality

The Republic of Brutopia are updating the design of their library cards with a new security feature: a 2D barcode containing a cryptographically signed copy of the human-readable fields on the card. ...
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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 ...