Questions tagged [database]

A structured set of data held in a computer, esp. one that is accessible in various ways.

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90
votes
8answers
27k views

How is CipherCloud doing homomorphic encryption?

Much of the literature and latest papers suggest that homomorphic encryption is still not practical yet. How is CipherCloud able to achieve this? Does anyone have an idea? Their website does not ...
12
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3answers
3k views

Salting when encrypting?

I was attending a database encryption session at a developers conference. The presenter (who was a published author on the subject) said that MS SQL Server did not support salted hashes in the ...
11
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1answer
989 views

Why x00 is usually avoided in salt?

In .NET Framework, there is a cryptographic Random Number Generator (RNG) provider which enables to generate a cryptographically strong sequence of random bytes. This provider contain, among others, ...
9
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1answer
3k views

Encrypting user data with their password?

I had an idea once that all of the user data (including the username) could be encrypted with the user's password. Obviously, most sites would store different data, so using the same password and ...
9
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1answer
1k views

Adi Shamir's secret database of all primes

I was going through these presentation slides (PDF) on Crypto 2013. It summarizes the paper, Factoring RSA keys from certified smart cards: Coppersmith in the wild. In the last slide, it was ...
6
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3answers
4k views

Which of these 3 AES 128 symmetric encrypt/decrypt routines is most secure?

I am developing a symmetric en-/decryption routine written in c# for a database containing user-specific, sensitive information. I have narrowed down the implementation to 3 different approaches, ...
6
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2answers
574 views

A lower bound on the insecurity of CipherCloud?

CipherCloud claims to support , among other things, searchable encryption. A bunch of speculation seems to suggest they did this via some breathtakingly incompetent means( unfortunately such ...
5
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2answers
3k views

Public key crypto instead of hashing passwords in a database

Suppose I want to keep a client's password database secure (not in plaintext), while still having access to the plaintext password. Now I generates a public/private keypair. Then I send the public ...
5
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1answer
3k views

Hashing passwords with a salt - why use different salt for everyone?

Given a database where we have usernames and passwords, we want to secure users' passwords by hashing them. We should not use only username and passwords in this hash, as someone having data from ...
5
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1answer
386 views

Two way encryption with random IV

I'm attempting to encrypt some information into our database to be later pulled back out and displayed to the user. Searching and reading up on different methods I found a post over at stack exchanged ...
5
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3answers
2k views

Searching over encrypted data [duplicate]

Is there any library/tool available which can allow me to search over encrypted data? I would like to encrypt data on client side, send it to cloud and perform search in cloud. I've been reading ...
5
votes
3answers
755 views

Cryptographic data structure: sparse array without membership test

I would like a data structure supporting two operations: $\mathsf{set}(k,v)$ and $\mathsf{get}(k)$, with the following properties: $k$ can be any number between $0$ and something impressively large, ...
5
votes
1answer
490 views

How can I store confident data with OpenID?

I want to make a system that needs to store some confident user information in a database. I intend on using OpenID for user authentication. I would like encrypt the data in a way that it can only be ...
5
votes
1answer
813 views

Are there any Implementations of Secure Indexes? [closed]

There are several papers about Secure Indexes, for Example "Searchable Symmetric Encryption: Improved Definitions and Efficient Constructions" and "Secure Indexes". ...
4
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2answers
2k views

Hash function used to find duplicate data, at what point is the risk of a chance match sufficient to switch to a stronger hash or bytewise verifying?

In a lot of data management systems, a hash is used as a kind of data fingerprint, with the intent not to cryptographically defeat an opponent, but to quickly identify duplicate data by seeing if ...
4
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1answer
2k views

Alternatives to HMAC + CBC?

I'm looking at using HMAC + CBC. The combination looks like this: ciphertext = AES256(text, k1) data = HMAC-SHA256(iv | ciphertext, k2) | iv | ciphertext Where: ...
4
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2answers
2k views

End to end encrypted web chat app with stored messages in database

I am working on a web app with an integrated chat. All chats can only occur between two users - not more, not less. I am very concerned with security, so I would like to encrypt all chat messages with ...
4
votes
2answers
855 views

Detect tampering of data

I have the following problem: There are $n$ users and each users fills in three data points per day, this are three integers between say $-10$ and $10$. I have access to the database and hence I am ...
3
votes
1answer
832 views

Encrypting data at rest using AES-GCM, where should I store MAC (Message Authentication Code)

I am trying to secure user's profile in database (data at rest). This user's profile is downloaded only after successful authentication at server (based on user's entered password and user name). The ...
3
votes
2answers
3k views

Generate a unique 64 bit numeric database key without collisions at $2^{32}$ birthday threshold?

What is the best way to generate a unique 64 bit numeric database key from a string? For example: if the string is a URL, you could generate a 64 bit key using SipHash or by truncating a SHA256 hash ...
3
votes
1answer
240 views

A set of key pairs and one hash to secure them

I have a simple problem: I have a set of users' ECDSA key pairs, and say I want to encrypt them with a simple algorithm. I have access to one variable that uniquely identifies the user, so I hash it ...
3
votes
1answer
2k 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: ...
3
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1answer
73 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,...
3
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1answer
1k views

Database and End-to-End Encryption

I'm currently designing a mobile/desktop application to synchronize some messages or notes. I'm searching for a way to secure it and to avoid letting the server be able to read the messages. My goal ...
3
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1answer
314 views

Secure method of encrypting data within a database

I'm designing a program which makes queries to a database stored locally which could potentially contain a lot of sensitive information. As such the information must be kept secure as possible from ...
2
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1answer
303 views

Is an IV useless for encrypting database IDs?

In my scenario I need to build a pseudo-anonimization service: a machine that given a plainID return a chiperID and vice-versa. <...
2
votes
2answers
246 views

Is the statement true in the context of AES-256 encrypted data stored on a hacked server?

I'm writing a document and I am making an important statement in it, which may be used for strategic decision regarding data-management (possibly from never handling sensitive information online to ...
2
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2answers
37 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 ...
2
votes
1answer
434 views

What is the best current way to cryptographically secure databases?

I'm currently working on a proposal for some secure complete system and one of the things currently lacking is the database security. However I don't want to roll my own crypto there and thereby need ...
2
votes
1answer
482 views

Can I use asymmetric encryption for more powerful write-protection?

I have a game that I am developing which uses a locally-stored internal database. It does not matter to me whether a user can read the file (which, to me, means I don't need a symmetric cipher), but I ...
2
votes
1answer
534 views

Do companies like CipherCloud really have the option to use homomorphic encryption?

I was reading How is CipherCloud doing homomorphic encryption? and was wondering: Is there a technically feasible way for companies like CipherCloud to use homomorphic encryption (HE) while ...
2
votes
1answer
138 views

Encrypting the relationship between two database tables

I'm not a cryptography expert myself, and know enough to know that I shouldn't design my own crypto schemes, so I thought I'd seek advice here. In an application, let's say we have two database ...
2
votes
2answers
364 views

Is this a valid “fix” for deterministic encryption in encrypted databases?

It appears (after doing some light research) that for encrypted databases to be practical enough to be usable, deterministic encryption is required, specifically with regard to the type of encryption ...
2
votes
1answer
43 views

Crypto scheme to map data to users in a way that is anonymous to database server

I am trying to finish a paper on censorship resistant data-sharing systems in semi-centralized ways. I know the below threat model can be mitigated by using decentralized system, but I am looking for ...
2
votes
1answer
39 views

End-to-end photo storage

I've been tasked with developing an app that will need to store photos a user takes securely, and I've been struggling to think up a method to do this. What I was thinking so far is as follows: When ...
2
votes
1answer
115 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 '...
2
votes
2answers
236 views

Search Over Encrypted Data

I'm doing a research about how to search over encrypted data as the title said. And, I saw cryptDB used a cryptographic scheme from Song et.al's article Practical Techniques for Searches on Encrypted ...
2
votes
2answers
245 views

How secure is a system that retrieves encrypted private keys from a public database?

The system in question is one with multiple users. Each user has a password associated with their account, and each user owns several public-private keypairs. A user's private keys are encrypted using ...
2
votes
1answer
1k views

AES Key Generation based on database guid

I am developing a .NET application spanning multiple servers who should all be able to decrypt data stored in a SQL database. My database is multi-company where each company has its own GUID. since ...
2
votes
1answer
103 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
votes
0answers
33 views

Is it possible to encrypt a user’s email in a zero-knowledge way and still send them emails?

This is kind of hypothetical, but let’s say I have a web app and I want to store a user’s email for sending notifications to. Is there any zero-knowledge way to hide their email from ourselves and ...
2
votes
0answers
117 views

P2P Website/Database Encryption Process

Sorry if this doesn't fit the guidelines, but I believe it is a conceptual issue that is not opinion-based and can be reasonably answered in a single authoritative answer (I'm also struggling to find ...
2
votes
0answers
394 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
217 views

Encrypted database: how to deal with general queries?

My question is quite related to the concept of homomorphic encryption, which is not practical at all nowadays. In short, I would like to know how to query encrypted databases. Simple queries which ...
1
vote
1answer
7k views

AES GCM symmetric encryption of data at rest in c#, ciphertext much longer than plaintext

I've written encryption/decryption routines using AES GCM. Code can be found here. I recently realized that the cipher text is longer than I believe it should be. It should add the tag and IV onto ...
1
vote
1answer
118 views

What are the possible security issues when exporting a plaintext database to a file like this?

Say I have plaintext database with key-value pairs of usernames and passwords. Then I iterate through the database, encrypt the passwords, and write the username and encrypted password pairs to file ...
1
vote
1answer
2k views

Creating unique keys with md5

The project I'm working on requires me to find a way to create a unique key based on data stored in a table. The table in question consists of x columns and y rows. In order to create the key I want ...
1
vote
1answer
92 views

Secure way to hash a lookup value

I want to securely store a database table that consists of an account ID and a few columns of sensitive data. The data only has value if it can be associated with the account ID. My thinking is to ...
1
vote
1answer
170 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 ...
1
vote
1answer
141 views

Tips on conceiving safe software messaging platform

I have a personal project in mind in which I plan to use cryptography in order to let the users be confident in the fact that, even if all data get's stolen, it would be virtually impossible to crack ...