Questions tagged [data-privacy]

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

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1answer
3k views

Applying machine learning algorithms to homomorphic encrypted data

I have a basic understanding of encryption and I got back to the topic because of an interesting site that encrypts financial data using homomorphic encryption (HE) and I would be happy for any input ...
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1answer
489 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 ...
9
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1answer
263 views

Secure multiparty computation of conjunction

Suppose Alice and Bob each have bits a and b, respectively. How can Alice and Bob compute the function ...
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2answers
825 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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2answers
2k views

NTRU crypto from unseen.is; myth busting help

I am always on the look out for privacy enhancing technologies. I stumbled upon the service from unseen.is. I had a look at their site (specifically here) and even though I lack knowledge there are a ...
4
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1answer
985 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
722 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 $D,D'$ ...
4
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1answer
93 views

Oblivious Transfer where neither party learns the index of the message

In a traditional Oblivious Transfer setting, the sender has a list $(x_1, x_2, ... , x_n) \in G$ where $G$ is the chosen group. The receiver has $b \in \mathbb{N}$, such that engaging in the protocol ...
4
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2answers
120 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 ...
4
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0answers
168 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 $r_1,r_2,r_3$ ...
3
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2answers
108 views

Hiding identifying data while allowing matching?

I do research with people about their illegal drug use, and for one project I'm doing surveys with them when they visit a needle exchange. So over time the same people get repeatedly surveyed as they ...
3
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2answers
79 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 ...
3
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1answer
453 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 ...
3
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1answer
94 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 ...
3
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1answer
219 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 ...
3
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1answer
192 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 ...
3
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1answer
150 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 ...
3
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1answer
678 views

How to enforce data privacy, integrity and authenticity of distributed firmware images for an embedded device?

I'm developing a bootloader for an embedded device, with which it should be possible for customers (i.e. device owners) to update the device's firmware. It is required that: the firmware is ...
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0answers
152 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 ...
2
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2answers
853 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 ...
2
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2answers
326 views

Privacy and Integrity in Public Cryptography

I'm trying to figure out which is the best way to get privacy and integrity together in public cryptography. Alice needs to send multiple files $f$ (may be big) to Bob. I've thought: Alice computes ...
2
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1answer
376 views

Government root SSL certificate possible vulnerabilities [closed]

I'm writing an article about new government law in Kazakhstan. The law was accepted in December, but now one of our providers announced information for small and medium business how to install ...
2
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1answer
67 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 ...
2
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1answer
948 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: ...
2
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1answer
144 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 ...
2
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1answer
82 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 ...
2
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1answer
99 views

Join Datasets While Protecting Anonymity

I've run into this issue a couple of times in my career. I'll see if I can explain with an example (please ignore the fact that this is implausible in the real-world). Suppose I sell computers, and I ...
2
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1answer
186 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 ($\...
2
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0answers
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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0answers
26 views

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 ...
2
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0answers
172 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 ...
2
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2answers
80 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. ...
2
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0answers
266 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 ...
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0answers
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 ...
2
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0answers
381 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 ...
2
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0answers
189 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 ...
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1answer
3k views

Ensuring integrity and confidentiality together with symmetric encryption

I've been required to answer a question: As usually, we have Alice and Bob. Suppose Alice wants to send a file F to Bob, ensuring integrity and confidentiality. They share a symmetryc key $K_{...
1
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1answer
214 views

On the privacy of perfect hash functions

I'm digging into the several algorithms for building (Minimal) Perfect Hash Functions. It seems that the recent works provide quite a few very efficient algorithms. However, I'm wondering how a (M)...
1
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1answer
92 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? ...
1
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1answer
230 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, ...
1
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1answer
98 views

Is the following aggregation scheme private?

Is the following scheme private? By private i mean an untrusted aggregator (UA) cannot reveal anything other then an aggregate function output on plaintext data Each party holds a secret key $k_i$ ...
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3answers
238 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 ...
1
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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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1answer
1k 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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2answers
897 views

Are SSL/TLS used for maintaining data confidentiality?

In SSL/TLS, we use symmetric and asymmetric keys to encrypt the data. Does that mean that the keys are used to encrypt the data (preserve the integrity) or provide a secure channel for the data to be ...
1
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1answer
168 views

Privacy-Preserving relational databases: checking the existence of a record (or multiple records)

I would like to know if there exists a protocol which performs the following operation in a privacy-preserving fashion: User $U$ wants to know whether a record is stored in the database. The primary ...
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1answer
351 views

Unique, anonymous online authentication

Is there a way to authenticate users online without knowing their real identity yet preventing them from registering twice? If not, what is the least amount of information you would need? If it helps, ...
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1answer
63 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 ...
1
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1answer
56 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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1answer
236 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. ...