Questions tagged [encryption]

Encryption is the process of transforming plaintext using a cipher into ciphertext to make it unreadable to anyone except those possessing the key. Decryption is the process of transforming that ciphertext back into plaintext, using the key.

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Alternate to distributing master key to every user in circle of trust

I am designing an end-to-end encrypted file storage system where only the user should be able to access their own data. The best I could come up with is a system designed around a master key that is ...
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Method for getting encryption keys from U2F key

There are a number of questions on this site about how/can you use a U2F key to encrypt something. The main problems with doing this are that U2F keys were designed for authentication, so all they can ...
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Identifying the exact encryption procedure by database hash

I was asked to develop an external user administration for a legacy system so that it could be integrated into company processes. This system is mostly written in Python, but also uses unmanaged DLLs. ...
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AES encryption question

If we consider the generation of keys as $$\begin{aligned} K_0 &= E_K(IV); \\ K_{i+1} &= E_{K_i}(A) \end{aligned}$$ Where A is a block of zeroes, and the ciphertext blocks are computed as ...
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Using Alberti Disks to Create a Strong Cipher

Could one use three different disks set at different positions and encrypt a strong message? For example: Wheel 1: A = J Wheel 2: A = E Wheel 3: A = B First letter is encrypted using 1 and then ...
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Is there a protocol for granting access rights to publicly stored encrypted data?

Alice is a data provider and Bob and Charlie are consumers. Alice has a set of data assets $A_*$. Alice wants to share some of her assets with Bob, some with Charlie (they are not necessarily mutually ...
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End-To-End Encryption w/o User Key Management

I'm trying to build an end-to-end encrypted cloud note-taking system but don't want my users to have to deal with any form of key management. Is there any way to achieve this? One idea is to have ...
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Problem with e-cash system with multiple banks

Say that many banks issue electronic cash of a particular type. If there is a malicious bank and user collusion, the malicious bank signs electronic cash for a particular user. This user then takes ...
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How to change the known ciphertext so the known plaintext is changed in AES CBC mode?

I already read a blog about the padding oracle and also some posts about how to change the plaintext but it didn't work out. So I have the encrypted cookie (AES_CBC): ...
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What is the most secure way to encrypt certain properties in logs

I would like to encrypt certain data before logging it. Currently, I use a private key and a static IV. Looking at generating a suitable IV I am concerned about the overhead in generating CSPRNG ...
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Storing secrets on a peer-to-peer network by splitting up AONT data

I've come up with a way to transform a stream of bytes such that if any single bit is modified, it cannot be transformed back into its original state. Here's how it works: Encoding Get hash ...
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I2P Tunnel Creation Build on Request Record Question en(de)cryption method

Not sure if anyone here can help, but if so, sure would appreciate the help. If we read the https://geti2p.net/spec/tunnel-creation documentation page on how I2P creates a tunnel, we can read on the ...
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Errors in LLL cracking knapsack crypto

I am attempting to try some sample knapsack encryption problems and the attack on them using the LLL algorithm. I am using here and here as the guides. They both provide examples to walk through, ...
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Time-based decryption service

i am thinking about building a public crypto service, yet at the same time, I am still quite new to crypto and therefore prone to snake-oil inventions I guess. My plan is to build a website which ...
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71 views

Chameleon hashes as encryption keys

I'm a newbie to cryptography and I have been wondering about the possibility of using Chameleon hashes as symmetric encryption keys. Here is my scenario and my thought process: Let us consider a ...
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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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Most energy-efficient authentication protocol?

I am looking for a cryptographic protocol that is as energy-efficient as possible. I am talking about battery drain. Alice wants to do a mutual authentication with Bob. Maybe symmetric is good, maybe ...
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What does libsignal use the registrationId for?

I am playing around with the libsignal at the moment and i was noticing that in the different documentation for libsignal-js or libsignal-java one of the first steps is always to generate a so called "...
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How to decrypt a simple substitution cipher where space is also encrypted by a character

I am trying to decrypt a text data encrypted with a simple substitution method with 2 steps. First, shift the alphabet of the source text by a few characters. For example, if we shift by 2 characters,...
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Deriving an encryption private key from signature private key

If I have a cryptosystem in which I require both signing and deriving a shared secret key for encryption, what is the recommended way of achieving that? Is there any vulnerability in generating a ...
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Using OpenSSL to emulate LTO 4 tape encryption

I have a mix of LTO 4 and LTO 3 tapes I would like to encrypt data on to. LTO 4 has built in encryption - load they key into the drive, and it handles the AES-256-GCM encyption transparently. LTO 3 ...
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Additive masking for encryption inside $\mathbb{Z}$

If I have to obfuscate my value $m$ from someone, then what is wrong with just showing them $m+r$ as an "encryption" of $m$. If someone would try to guess $m$ from it then it would require them to ...
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Perfect Secrecy and Message distributions

It is know that for a perfect secrecy scheme, for all m1,m2 and c: $Pr[C=c | M=m1] = Pr[C=c | M=m2]$ I also know that for all distributions of M, m1,m2 and c: $Pr[M=m1 | C=c] = Pr[M=m2 | C=c]$ Does ...
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Automorphism in Cryptography

I read a research paper in which the writer again and again writes about norm preserving automorphism such as $\left \| \phi(a) \right \|$ =$\left \| a\right \|$ and determinant preserving ...
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Is anyone using Half-Bit encryption? What is it used for now?

Long ago I learned about an encryption scheme which uses a random mask of bits which were "half on". I don't recall all the details, but basically, if a mask bit was a one, the input bit was passed ...
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Is there a reduction of security if I XOR Pkcs5S2 and SecureRandom?

I'm using this codereview sample to encrypt data. I would like to provide hardware protected encryption and a user password as the key. Is it acceptable to XOR the KDF Pkcs5S2 in Bouncy Castle with a ...
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Rotate values in predefined manner

I want to create a Server S1, that publish a different value every 10 minutes on the internet. The value looks something like f7826da6-4fa2-4e98-8024-bc5b71e0893e. ...
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Recryption of ciphertext with a different key

Let's have $P$ some sensitive piece of data and $K_1$a secret value, both known to Alice, but not to Bob. $K_1(P)$ means $P$ encrypted using $K_1$. Alice sends $K_1(P)$ to Bob. Bob keeps the value of ...
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212 views

Encrypt/Decrypt cloud passwords with master password

I know it's generally bad to store password in the clouds, and that I should be using salted-hashed password only. I'm making an application that will authenticate a user (with salted-hash), and then ...
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Permuted Hash Table

Suppose we have a hash table, $HT$, consisting of $100$ bins.The hash table uses a hash function $H$ that is public. We all know that given value $a$ we can compute the address in the hash by $H(a)=j$...
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When we use permutation and random long sting to hide a message

This question is modified version of this: Can we use merely permutation to hide a message? I have an English name $m=m_1 || m_2 ||..||m_{30}$. I pick a random string $d=d_1 ||..||d_{70}$ I mix ...
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Symmetric encryption with compression for MySQL DB data

I would like to compress data before encrypting and storing it in a MySQL DB to reduce especially bandwith requirements (compression reduces bandwith by 70-80%). At present, all is handled by a server-...
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Having doubt in Rijndael Algorithm- coding for decryption

I am doing a project on the Rijndael Algorithm. I have already written the encryption code which produces the correct output. Now I want to implement decryption as well. I'm doing using VHDL, ...
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Batch ElGamal Scheme

I know about ElGamal scheme and its key generation, encryption, and decryption methods. I'm not sure about what is meant by batch ElGamal. Can someone please clarify it. How it differs from ElGamal ...
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Is it possible to have E=D and Ke <> Kd?

Let us consider $E$ an encryption algorithm that encrypts a message $m$ into a ciphertext $c$ using a key $K_e$. i.e $c = E(K_e, m)$. Similarly, decryption is achieved by $m = D(K_d, c)$. Is there ...
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Defining correct secured channel from endpoint to server

I'm new to cryptography and have a question regarding encryption usage. The scenario is as follows: I have an endpoint hardware device (CPU - ARM A7 1.2 ghz) which runs Ubuntu 14.04. This hardware ...
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199 views

how to implement order preserving encryption except cryptdb

Which cryptographic algorithm is suitable for implementing order preserving encryption with out using cryptdb
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Can a combination of encryption algorithms weaken the overall encryption?

Are there any instances where a combination of industry standard encryption algorithms can weaken the overall encryption of the data? As a Naive example using non-standard encryption algorithms, ...
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436 views

Rabin cryptosystem with 1 mod 4

We have p and q which are distinct primes congruent to 1 mod 4. Then we have n = p*q. Do you know any algorith for calculating square roots for the decryption in this case? I'm asking for some ...
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Is ASCON cipher broken?

http://eprint.iacr.org/2015/030 present several attacks of ASCON but does not have a conclusion section. I'm having troubles estimating what are the consequences on the use of ASCON. What's your ...
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526 views

Brute Force AES Calculations

I have an encryption service in which the user decides the length and the type of key, so I would like to build a tool that educates the user on the brute force times for the key they created if using ...
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499 views

fuzzy commitment implemenation to make secure biometric template

I want implement some ideas from an article that is about making secure biometric templates using fuzzy commitment and fuzzy vault. I need to implement just the fuzzy commitment (fuzzy commitment is a ...
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How do i manage encryption keys with a cloud provider?

I would like to provision services from a Software as a Service (SaaS) provider. This is multitenant environment (multiple companies will be using a single instance of the application, with a single ...
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144 views

Cryptography system that limits the length of the encypted message

I have two devices which communicate via sms. This communication should now be encrypted. The devices can only send messages with the lenght of 160 characters. So i am looking for an encryption ...
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Niederreiter cryptosystem sources

I want to study about Niederreiter cryptosystem and I want your opinion about sources, papers, etc. I found stuff on the Internet but I want to know if there is a good source that you may know. I want ...
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XOR of users password Scrypt key and Random 32 bit salt?

I am trying to encrypt users private keys with the user password but if a user provides a weak password then the scrypt key generated from it will also be weak and suspectible to attack. Let say the ...
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How can I protect AES-256 encrypted data?

In April 2017, Jacob Henning asked "What are the chances that AES-256 encryption is cracked?" and part of his question was how best the transmitted data, now in his web database, a.k.a. "data at rest" ...
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Encrypt 2 numbers preserving arithmetic correlation

I want to encrypt 2 numbers using a public key and have the reader know the correlation between those 2 numbers. I can also share the public key. Example: ...
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537 views

how to encrypt the chat message with multiple people public key together and restore the message?

I have a application with two users and one middle man, all of them holding the private and public key, To make the secured chat, two users and one middle man are all sending the public key and ...
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Reversing key exchange algorithm

I'm analyzing some software and finding key exchanging procedure. Its looks like very similar with Diffie–Hellman, but not the same. I can’t understand the purpose of this. The step of algorithm is: ...