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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RC5 vs RC6 vs CAST128 vs Loki97 vs Mars

Yes, i know the question looks kinda weird but.. i dont know i could ask in different ways. Which one is the best (considering speed & security) of these? What does the scoreboard looks like? (Im ...
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Plz help to understand this paragraph . According to concept AES is not used Feistel structure but here both are used

In Dual Watermarking in Tele-radiology using DWT for Data Authentication and Security, the authors wrote: The encryption process uses the Feistel structure consisting multiple rounds for processing ...
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How can I do cryptanalysis on a chaos-based cipher?

I have been reading about chaos-based cryptosystems. Every designer claims that his design is a secure system without much cryptographic analysis; however, it turns out that this is a false claim in ...
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Is chaos-based encryption legitimate?

Is chaos-based encryption a rigorous discipline? And why there are objections to it within the cryptography community? And why are many of its cryptosystems weak? And does it has a promising future? ...
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Weakness of XORing random bytes with secret key

Side A generates 16 (high quality) random bytes and performs XOR with a 16-byte secret key, then data transfers to side B, where the same secret key is used to recover the original 16 random bytes. Is ...
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RSA DECRYPTION when N gives only one prime number

I am getting only 1 prime factor to some power if i factorize N for RSA decryption. So, in this case what will be the value of P and Q. P will be that one Prime Factor and then there is nothing left ...
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88 views

Decryption of an unknown cipher

How can I identify the cipher that encrypted the data shown below? I'm very new to this field, so I am not sure. For example: How does one know which cipher is used in the following line? How can one ...
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Decrypt RSA with known public key and modulus and the range of dp

How to decrypt RSA while given $e$,$n$ and the range of $dp$ ? ...
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Elliptic curve bilinear pairing parameters for 80-bit security level

I am reading a paper based on elliptic curve bilinear pairing groups. The author has defined the size of private key, public key etc in terms of $|\mathbb{G}_1|, |\mathbb{G}_2|$ and $|\mathbb{G}_T|$. ...
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Where to start? decrypting .enc files [closed]

I'm looking for a simple way to brute force a series of .enc files. My particular use case is that I have a CD containing purchased photos from a photographer that is no longer in business, and there ...
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Managing master keys used in PBKDF2 and HMAC (store, rotate)

My use case: I have few master keys, I use each for a specific operation (e.g. one for encrypting user's data and another for creating JWT signatures etc...). I use these master keys in two specific ...
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Should I protect the salt before storing it in a database or use a pepper (secret salt) instead?

If I protected the salt or used a pepper (secret salt) and an attacker got access to the database he can't do a rainbow table attack on a targeted user (a famous or important person). Should I use a ...
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What uses are there (if any) for asymmetric message encryption?

What uses are there (if any) for asymmetric encryption of a message, instead of hybrid encryption? Specifically, I'm not considering asymmetric encryption of a symmetric key (eg old TLS RSA key ...
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Comparing two private values and extracting the ciphertext corresponding to the minimum value

How can I solve this problem: I have a directed graph of nodes that can be malicious and all of them have a private value. Consider a node "B" with private value "BPrivateValue = b&...
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Does asymmetric order-preserving encryption exist?

As I understand from this post, mapping from plaintext space to ciphertext space is the fundamental point of all order-preserving encryption. So the only way that we let someone encrypt an arbitrary ...
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Can CPA secure scheme be converted to CCA secure?

I would like to know if there are some methods or techniques that can convert a public key encryption scheme from CPA secure to CCA secure?
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What is the correct order of operations for one-time pad cipher when using subtraction and mod 10 arithmetic?

What would be the proper order of operations for OTP encryption/decryption when using subtraction and mod 10? E.g. P - K = C or K - P = C Most of the sources I have seen do not cover this topic or I ...
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Zero knowledge RSA public key

Suppose Bob has $k>1$ RSA public keys $(e_i, n_i)$ without any knowledge of their corresponding private keys. Alice also has all the public keys, but also has a private key for only one of them, ...
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How does Authentication-Key Recovery for GCM work?

In his Paper "Authentication weaknesses in GCM" Ferguson describes, how some bits of the error polynomial can be set to zero, thereby increasing significantly the chance of a forgery. Q: ...
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Proving ownership of an encryption key

In the context of a host-proof storage service, is there an encryption scheme that allows me to prove to the server that I own the secret key to decrypt the ciphertext I am currently uploading but (...
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Factorization of polynomial in GF(2^128) used in GCM

It is widely known, that using a GCM nonce twice or even more often can be used to disclose the authentication key H. I understand, why this is theoretically possible. However, I have no feeling about ...
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The security level of secret share compared to homomorphic encryption

I want to compare additive secret share to Paillier encryption. However, I haven't found out how to set the parameters in such a way that the security level is consistent. Additive secret share (...
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Where exactly do you add the zeroes to a URL in a padding oracle attack? Also, how would you decrypt a file this way?

I have been studying various crypto attacks, and one of the attacks that I have recently studied was the padding oracle attack. Now, I mostly understand it, but there is one aspect of the padding ...
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Encryption of small data with fixed key and incremental IV

I have a Bluetooth device that sends a small package periodically (without receiving). I want to encrypt and authenticate the data using AES-128. It has an embedded random and unique key which is ...
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What is a ciphertext only attack and how OTP is unbreakable using this attack

I was wondering that what actually is cipherText-only attack and how the One Time Pad Encryption cant be broken by this attack?
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Does reusing IV in AES-CBC weaken it?

Rsynccrypto allegedly uses AES-CBC with a twist: If the last few bytes of plaintext meet a condition*, then stop, pad the current block and start encrypting new block from the current position in file ...
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How much much data can be verified by an electronic signature?

I’m trying to get a good understanding of how data encryption and signing work. I imagine these vary a bit depending on the software being used. In particular, I am wondering about this: how much data ...
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Key space of a substitution cipher

I was going through a cryptography course, and I found a question there that: What is the size of the key space of the substitution cipher with 26 letters? Its answer was 26! I am not sure what this ...
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How to encrypt using private key for ECC

As we know, ECC using $C_2 = r \cdot G, C_1 = M + r \cdot G$; and decrypt with $M=C_1 - K \cdot C_2$. And sign using point $X$: $X = k \cdot G(x_0,y_0)$. $r = x_0 \cdot K; s = 1 / k \cdot (M + r \cdot ...
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Factors calculation in RSA

You are given $d\bmod(p-1)$ , $d\bmod(q-1)$ , $\operatorname{invert}(p,q)$ and $p\bmod2^{200}$, the public exponent is $e=65537$. $\operatorname{invert}(p,q)$ is the answer of $ p*x \equiv 1 (mod\quad ...
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Completing RSA Encryption

Being new to cryptology, I'm trying to understand how I would complete RSA encryption by hand. I can only follow the formula so far before becoming very confused. I want to encrypt the value "123&...
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Nextgen firewalls - encrypted traffic inspection [migrated]

I read recently about next generation firewalls that use deep-packet-inspection, intrusion-prevention and something the manufacturers call encrypted-traffic-inspection. Can we explain intuitively how ...
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2048 vs 4096 bit RSA keys

I am in the process of creating an app which has secure encrypted messaging. I am generating RSA keys when the user signs up with key size 4096 right now. The problem is on the web these keys take a ...
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One-time-pad Encryption in C

I have been messing around with cryptography (for recreational use), and I created my own one-time-pad encryption script in C. Now, with that being said, I freely admit that I am by no means a ...
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AESGCM with arbitrary tag length in Java [migrated]

For algorithm test vector evaluation, I am trying to perform an AESGCM encryption and decryption with arbitrary tag length values such as 32 bits. When I try to initialize my cipher with such an ...
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XSalsa20Poly1305 for encryption at rest

I just found a project that used XSalsa20Poly1305 for transit and encryption at rest. I am trying to find some information if that is something worth trusting data to. It feels a little hard to put ...
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Why are block ciphers mostly used as stream ciphers?

Using a block cipher with using either CTR or GCM mode gives us a stream cipher, the only difference being that CTR does not include a MAC tag or AAD but GCM does. I think these are the most commonly ...
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Encrypted file sharing with deterministically generated key from user password

Background info: I need to encrypt files in a enterprise workspace with several users. The goal is to encrypt files directly from browser to be saved on a server and each user could decrypt files for ...
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Cryptography Challenge [closed]

I have been messing around with cryptography (for recreational use) and I have created my own function that encrypts things for me. Now, with that being said, I freely admit that I am by no means an ...
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Cyclicity of AES [duplicate]

It is known that AES is extremely secure, with its highest standard(AES-256) being able to protect the national secrets of most governments. Due to the nature of its steps, there's the question about ...
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Cons for stream ciphers that are based on hash functions

In an answer of here someone mentions: if you have a hash-function-with-oracle-powers, then it is rather easy to generate a pseudo random stream from a secret key, by hashing K||n where K is the ...
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is $F_{k_{1}}(m)||F_{k_{2}}(F_{k_{1}}(m))$ always a PRF? when F is a PRF

is $F_{k_{1}}(m)||F_{k_{2}}(F_{k_{1}}(m))$ always a PRF? when F is a PRF As an intuition it seems to me that the answer is "NO" as the two halves of the output depends on each other
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Prepare signing/verifying module from node js crypto

I'm working on a node crypt module that will signing/verifying. I have managed the verifying module: ...
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Is PRF XORed with its key still a PRF? (always)

$\forall k \in \{0,1\}^n,m \in \mathbb{M},F_k(m)$ is defined as follows: $F_k(m) = F'_k(m) \oplus k$. It is known that $F'_k$ is a PRF. Note: 𝕄 is the message space and it's assumed that the key $k$ ...
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How to protect a non-extractable Secret Key in indexedDB?

I have encrypted data in AES-GCM with the crypto API. The initialisation vector is then ...
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Encrypting full word using Paillier Scheme

I am using Paillier scheme to encrypt a message however, I have divided the words into alphabets and then convert each alphabet to ASCII code encrypting the final result. It works fine, but I want to ...
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Is the following derived MAC where the output is XOR'ed with the key secure?

Hey I'm wondering if the following scheme is secure or not , I tried reductions and some tries to prove that it not must be secure but I feel completely stuck . More details: It's just any reduction ...
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Prove data encrypted with different keys matches

Suppose user A encrypts some data using his public key and stores the data publicly. Later user A would like to transfer that same data to user B publicly by encrypting it using user B's public key. ...
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generic method/process to construct a cryptosystem based on the Decisional Problem

Suppose I am given a Decision problem(DP) which is proven to be NP-hard. Is there a generic method/process to construct a cryptosystem based on the DP? Thanks.
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End to end encrypted chat design

I am in the process of creating a flutter application that will include direct messaging. You can message 1 person or a group of people. I want this to all be encrypted for privacy. The method I was ...

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