Questions tagged [data-privacy]
Data privacy refers to (cryptographic) methods to prevent the disclosure of sensitive (identifying) information of persons.
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Question regarding post-processing Property of Approximate Differential Privacy
I am currently working with differential privacy and have a question regarding the composition of two DP mechanisms. In particular I am considering the following problem: consider having obtained a ...
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Flaws in modern file encryption
Assuming AES-XTS is used for encryption, the data has to be put into the algorithm first and probably processed in RAM. Which means that the unencrypted plaintext is somewhere in the dynamic memory. ...
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How to hide a sequence number in the messages that exposed to the public?
Here is the situation:
Alice sends msg1, msg2 and msg3 to Bob. Such messages are not always delivered to Bob following the same order. Bob needs to use key1 to decrypt msg1, use key2 to decrypt msg2, ...
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Is there any possible way to make each party obtain the output in a MPC protocol?
I konw a fact that it is impossible to achieve complete fairness in 2-party protocol from Cleve's paper.But i wonder if it is possible to achieve fairness in multi-party setting when the number of ...
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Assessing the security of the V2Ray ecosystem and its protocols
I recently came across tools like v2rayNG, described as "A V2Ray client for Android, supporting Xray core and V2Fly core," which function as VPN or proxy clients. These seem to utilize ...
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Implement true serverless (decentralized) online multiplayer game with cryptography
TLDR, this will be a discussion rather than my private problem.
Nowadays, most game developers or publishers have central servers to manage player transactions such as movement, mouse position, and so ...
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How to compute $r \cdot (a+b+c)$ for random $r$ and secret value$a,b,c$ in MPC?
Suppose Alcie,Bob,and Charlie each has a secret value $a,b,c$ respectively. they want to compute a value $r\cdot (a+b+c)$ together. $r$ is a random value, and all parties know nothing about it.
I ...
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Privacy-loss of an individual due their associated records
We utilize a differential privacy mechanism (Laplace noise, with scale $b$) to provide the privacy of records stored within a dataset. Each individual is associated with two, and at most $k$, records. ...
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Blinding an ECDSA private key without learning the private key
I am looking at ways to blind an ECDSA signing key (and verification key respectively).
Looking at proposed solutions like the IETF KBSS draft, and the IETF ARKG draft it seems that the ECDSA key ...
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Can DH be used for privacy-preserving proof of possession?
First time question poster so I hope the below is clear enough :).
Problem summary: Can a Holder and Verifier safely use ECDH for a Challenge-Response protocol where:
the Holder proves possession and ...
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Relating the noisy data to it's associated original/actual one
We have a set of query answers, i.e., $A = \{A_1, A_2, \dots, A_m\}$ and then we add noise to each of $A_i$ using a mechanism ($M$) providing differential privacy, i.e., $M(A_i) = O_i$. We denote the ...
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If the truncation function provides differential privacy
We have values in the range $[a, b]$, and we apply a differential privacy mechanism to add noise to these values. After obtaining the noisy values, we employ the following truncation function: if a ...
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Devising a system that allows for aggregate computations but does not hold the single values
First of all apologies if this is not the right place. I am not very knowledgeable in cryptography but I thought you can at least point me in the right direction of research.
The following is a toy ...
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"Select" query that provides differential privacy
We possess a database containing entries, where each entry consists of a person's ID and the corresponding fractional number $w$ (e.g., 2.34, 3.4, 12.3 etc) falling within the range of 1.00 to 100.00. ...
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Does 'digitization' of tickets always need private data? Or is it just data gathering? Any simple method without?
Many companies argue their gathering of private data with 'digitization' but I guess their real intention is most likely just gathering data. However I didn't came up with a simple idea without it.
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Is it possible to consider a mechanism without adding noise to provide differential privacy?
We have a set of secrets $S = \{x_1, x_2, \dots, x_n\}$ known to an adversary. Each $x_i \in S$ belongs to user $u_i$ who needs to obfuscate his secret, i.e. $K(x_i) = o_i$, using the notion of $d-$...
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How to achieve $d-$privacy considering some secrets?
We have a set of secrets $S = \{x_1, x_2, \dots, x_n\}$ known to an adversary. Each $x_i \in S$ belongs to user $u_i$ who needs to obfuscate his secret using the notion of $d-$privacy defined in the ...
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Why an adversary can guess a secret while we have provided differential privacy?
Let's consider a scenario with $k$-secrets, each associated with a user. Every user aims to obscure their respective secret using a $d$-privacy method.
We say a user uses $d$-privacy within a radius $...
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I'm wondering if using the same one public key does not guarantee privacy in the computation of multiple data owners
Participating entity: multiple data owners, computing clouds
Protocol: The multiple data owners send their data to the computing clouds, which perform the computation of the data.
Privacy protection:...
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How to avoid sender modify the final output in private set intersection under malicious setting?
I'm relatively new to this topic, and I have a question that might seem basic. I appreciate your patience.
In most PSI schemes(2 party or multi party),the intersection result is always output by only ...
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Ensuring Data Security During Decryption and Re-encryption Process
Scenario:
Consider a scenario where Server 1 stores a 600-800 KB ebook encrypted with a certain private key. Server 2, a computation-purpose server, holds this private decryption key and get access to ...
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Answering boolean question without knowing "Who" answer [closed]
Can cryptography solve this problem?
Two people are chatting, Mr. X and Ms Y. They give each other a CRC16 hash of someone's name initials and salt a random number at the end (suffix).
Ms Y: "I ...
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who creates the passkey (and how many will be created)? [closed]
Passkey is nice. The math is nice. The tech is nice. https://security.googleblog.com/2023/05/so-long-passwords-thanks-for-all-phish.html
What I still dont see after sooo many hours: what software ...
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Verification in Bulletproof commitment scheme
I am reviewing the ZKP course, represented by the university of Berkley (https://zk-learning.org/). In pages 44 of lecture 6 that is attached below (https://zk-learning.org/assets/lecture6.pdf), the ...
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Utility Guarantee of Small Data Base Mechanism in Differential Privacy
I am reading Section 4.1 (An offline algorithm: SmallDB) of The Algorithmic Foundations of Differential Privacy by Dwork and Roth. I am stuck at the proof of Proposition 4.4, which is about the ...
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Poly-commitment based on Bulletproofs
I am reviewing the ZKP course, represented by the university of Berkley (https://zk-learning.org/). In pages 41 and 42 of lecture 6 that is attached below (https://zk-learning.org/assets/lecture6.pdf),...
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Protecting value decomposition risk in microdata release
Consider a scenario where a company wants to release a microdata of their employees total annual compensation for the following year to an analyst in a recruiting firm in order to provide an ...
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How to solve the problem of FHE ciphertext expansion?
FHE typically has large ciphertext expansion factor, meaning that the ratio
$$\frac{|\mathsf{Enc}_{pk}(m)|}{|m|}$$
is typically quite large --- in standard schemes it is $\omega(1)$. Even getting $\...
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General Questions on Big Data and AI privacy [closed]
All,
Recently, I came across a question on privacy for big data and AI.
IMO, big data privacy focuses on "anonymization" aspect where sensitive informatino such as Personal Identitfiable ...
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SMCQL practical examples
I am looking for some practical examples on how to use SMCQL on some typical SQL queries. The paper seems to be oriented more towards theory. Can somebody point me to some examples to understand it ...
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IKEv2 with EAP and use of anonymous identity
IKEv2 RFC7296 Section 2.16, provides overview of how IKEv2 is used with EAP. That section states the following when a different identity (IDi) is used in message 2 IKE_AUTH from initiator to responder,...
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Zero-knowledge data storage with peace of mind. MAC/Encryption with two keys?
Background
Bob's goal: Receive data E = E(D) (encryption of D) from Alice that he knows for sure is encrypted and that he can't possibly decrypt (without brute force). This gives his data backup ...
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Approximate differential privacy: avoiding composition in vector-queries
Assume we have an $n$-dimensional real-valued function $f$ whose $\ell_1$ sensitivity is equal to $GS(f) = 1$. We can also assume the sensitivity of each dimension is also $\Delta f = 1$.
For pure ...
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Differential privacy with strong composition under k-mechanisms with different (ε, δ)-DP bounds
The overall DP under the strong composition theorem for k-mechanisms is ($\epsilon \sqrt{k log(1/\delta)}$, k$\delta$) such that each individual mechanism has ($\epsilon, \delta$)-DP.
But what if say, ...
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Constraining the output of a hashing function to a specific group
I looked into this paper on privacy-preserving aggregation by Marc Joye and Benoit Libert (https://www.ifca.ai/fc13/proc/3-3.pdf). A key element in their scheme is a hash function defined as $$H: \...
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OTP like Identity
I am a developer with very little experience on the crypto part,
and I'm looking for a secure solution (OTP Like) for identifying between client (browser) and server.
this is what i need:
Web Page at ...
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What do you think of my plan to secure on-chain sensitive data using asymetric encryption?
I’m new to development using web3 technologies and I have a use case where I want to store private data about the user in the public blockchain Polygon.
This data should be recorded to be tamper proof ...
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Privacy that a scheme offers
I encountered the following scenario in development of a system.
A user wants to perform an operation on one of $n$ days. An adversary can observe a sequence of integers $X_1, \cdots, X_n$. If the ...
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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 ...
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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 by internal processes that ...
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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, ...
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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 ...
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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 ...
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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 ...
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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? ...
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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 ...
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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 ...
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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
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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 ...
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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 < ...