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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Can I encrypt a message by swapping bits in the text?

I have tried out an encryption method, in which I swap bits in the text. The text length is N bit, then I generate several random number pairs in the range 0..N-1, as [n,k] pairs. After that I swap ...
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Does having a hash of a password jeopardize the security of plaintext that was encrypted with that password?

A malicious actor wants to decrypt ciphertext that was encrypted with a password. He also possesses the hash (bcrypt/PBKDF2) of that password. Does he have any significant practical advantage in ...
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ECRYPT Salsa20 Test Vectors Interpretation

I am currently implementing Salsa20 for my bachelor thesis. After having verified all the functions needed for the final encryption function with the given test data in the specification from DJB, I ...
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RSA assumption and relationship given by generating elemts of a Cayley graph

I have read a very interesting description of computation related to the RSA group as follows. "By the Chinese remainder theorem, we have that: $$(\mathbb{Z}/pq\mathbb{Z})^* \cong (\mathbb{Z}/p\...
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hacking encoder [closed]

you need to crack the encryptor. The code is written in C ++. I managed to find out what the weakness is in the key schedule. S-boxes and mix columns are not random. A hint can also be how the pdf ...
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How do you find the cipher formula for a cipher like this?

I'm new to ciphers and cryptology in general, so apologies in advanced. ((When I say I'm new, I mean I only started looking up cryptography in response to being given this cipher this morning, so I ...
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1answer
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Why is it secure to reuse key and nonce in ChaCha20-Poly1305 AEAD construction?

While looking at the ChaCha20 and Poly1305 AEAD construction as defined by RFC 8439, more precisely its use of the key and the nonce, I came up with the questions below. Maybe someone with some in-...
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Need answers to some questions I'm curious about [closed]

When more computational time is required to encrypt or decrypt the plaintext or cipher text? Which parameter reduces the performance speed of the cryptographic algorithm? How can we improve that ...
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number of operations for Elgamal cryptosystem

In page 408 of Hoffstein, Piper, and Silverman's Introduction to Mathematical Cryptography, it says "Roughly speaking, in order to achieve $k$ bits of security, encryption and decryption for ...
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How can I find the key if I have Plain text and Cipher Text [closed]

I'm trying to obtain the key with plain text and cipher text. I guess the encryption algorithm is Vernam Cipher as it works with binary data rather than letters Plain text : 1011 0101 110 Cipher ...
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1answer
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Can I use the secret part of a asymmetric encryption keypair as a symmetric encryption key?

Background I'm working on a framework for crypto-based authentication and authorization that is largely inspired by the way Keybase's Teams product works. Keybase uses the same process to generate ...
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Diffie-Hellman Decryption with A, B, p, g, cipher Parameters

I have a Crypto assignment, trying different ideas for couple hours landed me nowhere. Supposedly during a Diffie-Hellman key exchange Alice sends bob an encrypted message, the message (cipher) is a ...
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1answer
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RFC 4493 (AES-CMAC) algorithm with 256 bit key

I apologize for the newbie question. If I were to use a 256-bit key and AES256 (assuming I had the function instead of AES128, the length of the for loops in the functions xor_128, leftshift_bit, ...
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1answer
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Implementing BFV Relinearization

I'm currently working on a Python implementation of the BFV[12] cryptosystem. I got to a point where key generation, encryption, addition and decryption works as expected. Where I'm struggling with ...
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What different type of code should I use to decode this string? [closed]

Just saw this string of letters: picture here's a raw text version: ...
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1answer
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Encrypting a string of arbitrary size with a big integer

I am currently writing Python script that initiates a secure handshake. I am kind of reinventing the wheel here, so that I can properly learn it. Now, I have Diffie-Hellman mostly working from ...
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Encrypt files on harddrive with double encryption

So I've been stuck on this question for a very long time. How do you use double encryption to encrypt a hard disk so that all of the following conditions are met: All data on the hard disk is ...
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1answer
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Is MAC process different for symmetric and asymmetric?

Message Authentication Code as far as I know works on the shared secret key. Do they work in the same way. Is there no difference between symmetric and asymmetric processes. Can anyone please explain ...
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Are My Answers for This RSA Question Correct?

I am very new to cryptography and so I am looking for feedback on this question on RSA. Please let me know if I have made any mistakes, Thank you! (a). RSA Algorithm: -choose two primes p,q -...
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1answer
156 views

Why when I perform RSA 5 times do I get my original input back out?

If I perform RSA on my input 5 times, I get the original input back out. Why is it that often, iterating RSA encryption just a few times cycles yields back the original value, when the public modulus ...
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Are there any known problems performing a One-time pad with 2 keys stored separately - AKA 2 part Symmetric key exchange over TLS

If this is something that already has a name, please tell me to look at that, but I have not been able to find one yet. I am considering this process for storing some data securely. I want to ...
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1answer
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SCP03 - Does it always to depend on pre-provisioned static keys?

I am trying to understand Secure Channel Protocol 03 from specified by Global Platform and have seen a few implementations. From the standard: Session keys are generated to ensure that a different ...
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Symmetric Or Asymetric- When to use?

In block chain, we use asymmetric cryptography to generate public key which we send to receiver so he can unlock the funds. All other type of hashing for creating nonce, block id, merkel route, ...
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Should I update my fedora encrypted system?

I have installed my Fedora Workstation version 23 using native disk encryption. Since it, I am upgrading it using dnf system-upgrade plugin. Today, I have fedora 32. Some time ago, I’ve discovered ...
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Find the key of an XOR cipher with multiple messages from the same key

For example, I have three messages, each known to be XOR encoded, and each have used the same key for each message for the XOR cipher. Encoded Message 1 (e1): 00100111010 Encoded Message 2 (e2): ...
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1answer
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Do 64-bit ciphers still have use under very limited attack models?

If we have a very performance critical interactive session, like a video game, running on a trusted platform (video game console). If our goal is to prevent exfiltration of up to date information (...
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1answer
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RSA and the strong RSA assumptions

The RSA assumption: Given a randomly generated RSA modulus $n$, exponent $r$ and a random $z \in \mathbb{Z}_n^{*}$, find $y$ such that $y^r=z$. The strong RSA assumption: Given a randomly chosen ...
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Design flaws in the round-key generation mechanism of Data Encryption Standard (DES) [duplicate]

I am beginner in Cryptography, I want to ask that what are two design flaws in the round-key generation mechanism of Data Encryption Standard (DES) that can lead to the occurrence of weak and semi-...
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How to implement a Hybrid cryptosystem via GnuPGP?

I would upload some file on the cloud and share to my friends (more than one), securly. Reading on wikipedia I found an explication on how it works, but I have doubs, because I don't understand if I ...
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In veracrypt, what happens if you select “none” in file system options when formatting a volume? [migrated]

hey guys i searched google reddit r/veracrypt and the veracrypt guide https://www.veracrypt.fr/en/Documentation.html and couldn't find an answer, but i wanted to ask, when you have the option to ...
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E2EE encrypted chat where messages are only readable by participants and admin users

As the title suggests, is there a way to have an E2EE chat between two users, and have them be visible later by an admin user. I know this defeats the point of E2EE, but i want to have the messages ...
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3answers
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Differences between hashed text and encrypted text

I was wondering if it's possible to tell if the text is hashed or encrypted. For example, if someone has given you a a chain of random characters. Would you be able to tell if it's encrypted? Which ...
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1answer
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How to calculate RSA Key Size correctly starting from 384 bits to 15360 bits or beyond 15360 bits

Hello fellow experts here, I am new to cryptography. Recently I looked into RSA Key Size (Microsoft RSA library), it actually describes that the minimal key length required is 384 bits and maximum ...
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How to encrypt a message such that it cannot be decrypted before a certain time?

Suppose you have a message $m$ and you want to design a protocol that produces an encrypted message $c$ such that it cannot be decrypted before a certain time $t$ has passed from the encryption. How ...
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How to calculate degree of confusion of an encryption algorithm?

I am programming an encryption-decryption model in python 3. I want to check its strength. I found 3 methods to check, they are: 1. Degree of diffusion 2. Degree of confusion 3. Integrity check For ...
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Confused in selecting the encryption method for mobile number and email encryption

I'm new in cryptography and I'm developing a mobile app that gets user_name, E-mail ID, and ...
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1answer
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In two-dimensional even parity, how do we determine the corner parity bit?

In two-dimensional even parity, how do we determine the corner parity bit? Here's an example: ...
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1answer
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SHA-256 for unique token

I need to create an unique token for a web service. I'm doing that in the following in the following way: ...
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Difference between LRW and XEX modes

LRW and XEX modes of operation look similar. They are both tweakable narrow-block encryption with XORs before and after each single-block cipher. I didn't really get the point where they differ or ...
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What is the best encryption algorithm for having a “master” decryption key

I'm kind of a noob at cryptography so sorry if this doesn't make sense. Here is my scenario: Somebody inputs their email into a form, their email is encrypted and only they have the decryption key to ...
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Is XEX/XTS good for deterministic file encryption?

My understanding about XEX/XTS mode is limited. But from what I see, it has two good properties: It is length-preserving so that encryption doesn't cost additional space. It is deterministic, which ...
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Secure asymmetric encryption with 32byte ciphertext

I need securely asymmetrically encrypt the up to 16 bytes plaintext and receive up to 32 bytes ciphertext. I found that ElGamal produces ciphertext that is 2 times keysize. So I would need to use ...
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2answers
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As an analogy to asymmetric key encryption, does the following work? If not why not?

public key... a padlock (anyone can lock it) private key... the key to the padlock (only key owner can open it) Alice and Bob each have their own padlock and key Anyone can get a replica of any ...
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How to setup secure communications using AES-256-GCM?

I need to have a way to communicate securely over a local network. There are two computers, computer A and computer B, computer A is the server and B is the client. B opens a channel to A, at which ...
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1answer
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Problem with RSA deciphering

I don't quite get the algorithm yet. Sometimes it works and other times it doesn't,so clearly I am overseeing or misunderstanding something. I will just write what I did. My $N=143$ and has factors ...
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2answers
191 views

Encryption method that reduces the cipher text to a single byte

Has anyone encountered an encryption method that compresses the cipher text to a single byte at the expense of inflating the key. If yes does it have a practical use?
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Is there a crytographic scheme for this problem?

I a problem that essentially boils down to the following: There is raw data, D, encrypted with key K (call its encrypted form <...
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How does SHA-256 algorithm work

I want a worked example of the algorithm from start to finish. As simple as possible.
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Finding the relationship between generating elements represented by a Hamiltonian cycle of a Cayley graph (like in strong RSA condition)

Consider an undirected Cayley graph of a finite group $\mathbb{Z}_p \times \mathbb{Z}_q$, where $p$ and $q$ are distinct primes. Let the generating set for the Cayley graph be $S=\{g_p, g_q\}$, where $...
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1answer
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Encryption & decryption in AES CBC mode - Which is faster?

I wrote a small code to compute the time consumption by the AES in CBC mode, I noticed that the encryption is faster than the decryption, my question: Is my result correct? If yes, why is the ...

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