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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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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The goal, the method, and the interface of the signcrypt primitive.

Some time ago, I proposed making the site more educational by teaching correct cryptographic programming. The proposal had had somewhat good reception, but was met with cold ice as there had been ...
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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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38 views

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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146 views

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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203 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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120 views

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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89 views

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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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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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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Requested to encrypt data with AES256, digital certification, timestamped

at my job we have been tasked by gov to encrypt some data we send to them. The "law" says we have to do the title above, but they only need us to do the AES256 thing because the data is not really ...
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341 views

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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522 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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498 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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ECC decryption given $C=k*G*m$, $k$ and $G$

Suppose we are on an elliptic curve, given base point $G$, private key $k$, point $C=(k*G)*m$, where $m$ is a random number. Is it possible to recover $m$ (or some equivalent form of $m$)? If so, how?
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IND-CPA security adding two cipher

I am working on a proof in which the addition of two IND-CPA scheme adds two ciphers and generate the cipher as C = C_1 XOR C_2 The schemes that generate the C_1 and C_2 both are IND-CPA How can I ...
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How to do cryptography without knowing computer science or AI?

I'm interested in ciphers, codes, patterns, and mathematics, but do not have extensive computer programming acumen (VERY basic Java skills). I know nothing about machine learning, AI or anything in ...
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How to show that Affine crypto have a valid decryption

I just need to know how to attack a question I have in my textbook this is like: Let $E_1 (x) \equiv 17x + 7 \pmod{28}$ and $E_2(x) \equiv 23x + 11 \pmod{28}$ be encryption functions for two ...
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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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131 views

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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103 views

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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523 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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87 views

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: ...
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669 views

RSA : if my key and message are too large , how to do?

I want to send a message consisting of a string of number (e.g: 124124134235235) Then, p:125243 q:56454547 e: 2659043 d: 5261378624675 However, it will be too large...so, is there any solution to ...
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368 views

GMW Protocol with semi honest adversaries

I know the GMW Protocol is secure in the case of a semi honest adversary which control all the parties except one. However I want to proof that it is also secure in the case the semi honest adversary ...
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71 views

Integrity of Voice packets/ Audio signal

for encryption data packets, one should use GCM, CCM or EAX mode of operation to have confidentiality and integrity. What to do in case of voice packets? is it enough that audio signal gets compressed ...
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How to make sense of the decryption formula for Affine ciphers?

Hi guys so I'm investigating Affine ciphers and I need to understand a field of mathematics I'm not familiar with, which is modular arithmetic. The formula for encrypting a letter $x$ using the affine ...
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Encryption algorithm designed to be easy to decrypt by machine but impractical to decrypt by hand

I am looking for - or considering the design of a new - encryption algorithm that does not use variable keys, such that it is easy for a computer to encrypt and decrypt any message regardless of its ...
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487 views

Having plaintext and ciphertext, how can I learn more about key/encryption?

I have an OLD work database that seems to have a simple encryption on the PW. I have one users whose pw is 7777 the cipher text is ...
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296 views

FEAL-4 Fk Function 4 Rounds

As I understood in FEAL-4 it needs 4 pair of round keys. Which means that we need to launch Fk function 4 times. My problem occurs starting the 2nd round. At the first round we have the original 64 ...
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Are there any web puzzles I can solve without programming knowledge?

I don't know much about computer programming (taking an Intro to Computer Programming course at school), but discovered Cicada 3301 and was hoping there is something similar I might pursue for my own ...