Questions tagged [cryptanalysis]

Analysis of individual security aspects of a cipher or algorithm, not the security of a cipher or algorithm in general (which would lean towards “algorithm-design”).

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How is the 'Algebraic Degree' calculated in the paper about analysing the white-box AES(Chow et al. 2002) by exploiting internal collisions?

This paper proposed a new attack on the initial white-box AES implementation of Chow et al. In order to determine the good solution, we use the particular structure of the function $S_{0}$. $S^{-1} \...
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Kernel attack on MinRank - How do we check if we can stop?

I have some trouble understanding how Kernel Attack to MinRank is implemented. MinRank: Let $k, n, r$ be positive integers, and let $M_0, M_1, \dots, M_k$ be $n \times n$ matrices with entries in a ...
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The Probability to Detect or Identify an Unknown Ciphertext

Let $\it C$ be a ciphertext such that we have no information about the type of symmetric encryption algorithm used to generate $\it C$. Let $\bf S$ be the source bank of most block and stream ciphers ...
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RSA algorithm implementation

$$m^{ed} \equiv m \bmod n$$ $n =pq$, so by Chinese Remainder Theorem it is equivalent to $$m^{ed} \equiv m \bmod 𝑝, m^{ed} \equiv m \bmod q$$ where $n=p\cdot q$ So how did 2 come from 1 by the ...
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cascade encryption - If I encrypt my data using many different encryption algorithms

If I encrypt my data using many different encryption algorithms (using different passwords) how will an adversary be able to decipher the message?
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Time and Space complexity of MiniAES

I am currently doing my masters research on security of wireless sensor networks, the topic is "ENHANCING THE SECURITY OF WIRLESS SENSOR NETWORKS BY COMBINING GEOENCRYPTION AND LIGHT WEIGHT ...
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Composing subexponential L-function

Suppose $y=f(x)$ and $z=g(y)$ such that $y\in L_x[a,b]$ and $z\in L_y[c,d]$, where $L$ is the usual sub-exponential asymptotic notation $$L_x[a,b] = \exp\left((b+o(1))(\log x)^a(\log\log x)^{1-a}\...
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Advantage of existing Cryptosystems

I have read about the concept of perfect secrecy and statistical distance. The perfect secrecy is impossible to be implemented on real world scenario. So the cryptosystems used at various websites ...
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734 views

Introduction to LLL algorithm applied to linear modular inequalities

What is the Lenstra–Lenstra–Lovász lattice basis reduction algorithm about? How is it applied to solve for $x\pmod m$ a system of modular inequalities $(u_i\,x+v_i\bmod m)<w$ for $0\le i<n$? I'm ...
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What would be the most recommended AES && RSA Keys for production?

While I am a front-end developer and not a security expert programmer, I am worry about the keys I am using for my AES && RSA encryption. Please help me to understand: Is the following keys ...
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243 views

Reverse Java seed using outputs generated from nextInt(6)+1

Given a set of numbers within the range of 1-6: [3,4,3,4,5,6,2,3,1,5,2,3,6,2,2,3,3,6,6,4,5,2,5,3,5,2,4,4,2,6,3,6,1,5,1,3,6,1,1,2,2,4,5,3,1,2,3,4,4,6] generated using Java's nextInt(6)+1, is it ...
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Fisher Yates on "faulted" random number generator cryptanalysis

For the sake of curiosity and fun, i have implemented a C# program that operate as deck dealer on 40 cards deck (following the Fisher Yates shuffeling algorithm https://en.wikipedia.org/wiki/Fisher%E2%...
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Are there any Cryptography Algorithms that involve Lots of Number Theory?

I am looking for a good, meaty cryptography algorithm that involves a good amount of number theory in which I can explore. I'm researching, and AES (Advanced Encryption System) seems interesting, but ...
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204 views

Getting to understand the linear approximation of DES

I will make a presentation about Linear approximation (Matsui's paper 1993 Linear Cryptanalysis Method for DES Cipher ) of DES and I don't understand some parts of it. Here my questions : In the ...
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1answer
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Can we possible to solve the LPN problem using Arora-Ge algorithm?

I recently studied how to solve the LWE (learning with errors) using algebraic relations proposed by Arora and Ge (paper : New Algorithms for Learning in Presence of Errors). As I understood, for LWE ...
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Why this isn't a secure PRF?

Given that F is a secure PRF in the example $$F'(k,x)= F(k,x)\mathbin\|F(k,F(k,x))$$ I'm not sure why this isn't a secure PRF? Under what condition $F(k, F(k,x))$ when concatenated to $F(k,x)$ the ...
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How to prove document ownership at a specific time [duplicate]

Problem Given any piece of data, I could sign it with public key and made available online. This proves I am in possession of given data, but it doesn't tell I am the creator. The only possibility (I'...
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Can I derive IV, if I know Encrypted Txt, Key and Encryption Method?

I want to know is there any way to derive the initialization vector, if I know all the other details. AES SHA 256bits CBC pkcs5padding Input: Hello Key: 123 Output: xORGCDL88sa8cUrK8JNSCQ== Now, how ...
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Will cryptanalysis always stay a relevant topic?

I hope this doesn't look like a silly question. In an age where our current cryptography is often impossible to crack when properly implemented and used, would we be able to decipher anything, for ...
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Reusing encrypted message on MITM attack?

I'm using RSA public key private key for sending AES key from each client to server application. then i'm using this AES key and IV for communicating between client and server. what should i do for ...
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1answer
119 views

Disrupting MITM attack against 3DES by intermingling plaintext and inter-mediate ciphertext between rounds

Let's say someone implements 3DES with three separate 56-bit keys and an attacker is attempting to execute a MITM attack. Here is the encryption plan designed to attempt to disrupt the MITM attack, or ...
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1answer
363 views

AES-CTR security if S-boxes substituion is omitted?

I understand why s-boxes are needed in general especially when ECB mode is used(because of using the same key for encryption of other blocks)but I wonder if it's ...
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192 views

Why would you want to keep the Initialization Vectors Public?

So I was researching Initialization Vectors (IV) and even took a look at this thread... What is the main difference between a key, an IV and a nonce? ,but I was hoping that I could get some clarity. ...
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Decrypting an AES string

I'm dealing with a website that loads a javascript file which eventually sets an AES hash/value (whatever it's called) as a cookie. The file is heavily obfuscated making it hard to understand certain ...
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234 views

Double permutation patterns for transposition ciphers, how to crack

I'm reading from Cornell , I know for a single permutation, I can find the ciphertext length (100), divide in some key lengths (10x10, 5x20), then try all permutation (10x9x8... 5x4x3x2x1). then find ...
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321 views

Can you break a Vigenere cipher with key length of 2 and message/cipher text length of 4?

I am currently working on a problem where an attacker knows that a user's password is either "pqrs" or "jmlo" and also knows that the encryption scheme is using the Vigenere cipher ...
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1answer
64 views

Security of a custom AES-based attack model

Provided that: $AES(plaintext, key)$ is the standard AES block cipher for a 128 bits block. $\oplus$ is the standard XOR operation. $K$ is a constant 128 bits pseudorandom value, which is used as the ...
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Breaking vulnerable ElGamal encryption

In a ctf, I encountered this problem: ...
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93 views

Are these two methods of differential cryptanalysis different?

I'm trying to understand how differential analysis works. I'm reading this and this tutorials, but it looks like they do different things. In the first paper author tells us to bruteforce last round ...
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Differential analysis for dummies, how key position impact on tactic? [closed]

Im new to cryptoanalysis and started reading A Tutorial on Linear and Differential Cryptanalysis. The author is trying to explain it as simple as he can. But I still got some questions, can anybody ...
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Which encryption algorithm is sensitive to an attacker having access to it?

We are contemplating hiding a sensitive information from our business partner by encrypting it. However, customers have access to both the sensitive and the encrypted information. Furthermore, they ...
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106 views

Find first two blocks of plaintext given a final plaintext block, the IV and ciphertext for CBC?

I have the following: complete ciphertext; iv; last block of plaintext including the padding which is 04040404. The encryption was made using AES-CBC-256. I can ...
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1answer
78 views

When attacking keyed algorithms, how is it known when the output is correct?

I've been reading a little bit about cryptanalysis, and I'm wondering how attacking algorithms that work on keys is performed. It's obvious how algorithms like MD5 are attacked, in pseudocode: ...
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551 views

Identifying correct cipher

I am trying to decrypt a text(~900 characters) and I started with the assumption that its a Vigenère cipher as the one of the identifier tool identified it as Vigenère cipher and also the Index of ...
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268 views

Is this permutation secure?

Let vector ${\bf d} \in \{ \pm 1 \}^n$ be the message we want to send. In my system, ${\bf d}$ is multiplied by an $n \times n$ Fourier matrix ${\bf F}$, as follows $$ {\bf x} = {\bf F} {\bf d} $$ ...
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1answer
117 views

How much information do I leak if I upload multiple ciphertexts with cleartext overlaps?

Suppose that $t_1, t_2, \ldots, t_n$ are my clear texts. Suppose that for any $(i,j) \in \{1,2,\ldots,n\}^2$, $t_i$ and $t_j$ only differ in, say, the 1st $m$-many characters. Finally, suppose that I ...
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151 views

are outputs of sha256 independent when padded with different seed each time, in other words, when inputs can be somewhat related

So I was wondering about what will be the dependence of the outputs when I padded one input with two different strings two times for technically generating two different strings, say the input string ...
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Examples of multi output bit balanced Boolean functions

I am trying to find out and learn more about Balanced boolean functions. Wikipedia states that " a balanced boolean function is a boolean function whose output yields as many 0s as 1s over its ...
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Is the one-time pad secure if the key is computed so the ciphertext will consist only of "A"?

I recently learned about the one-time pad method, which has perfect security if the following conditions are met : The key must be truly random. The key must be at least as long as the plaintext. The ...
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Understanding Linear Cryptanalysis

I'm reading about the linear cryptanalysis of an SPN and I have some questions about the practicality of this. The example I'm looking at is from 3.3.3 of Stinson's Book and I believe the same example ...
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RSA PADDING WITH e=3 [duplicate]

I have a ciphertext which has been padded with spaces from left the message is 31 bytes long and e = 3 how can I recover the message with python code .
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689 views

Frequency Analysis on DES, AES, 3DES using Cryptool2

I am trying to analyze symmetric block ciphers like DES, 3DES and AES, using Cryptool 2. I want to do a frequency analysis on each of these ciphers, in order to comment whether this is an effective ...
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1answer
258 views

Is AES without T-Tables nor S-Box resistant to side-channel?

T-Tables and S-Boxes are prone to side-channel attacks, is an implementation without any lookup tables resistant to side-channel ? In this answer, https://crypto.stackexchange.com/a/63520/80926, the ...
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Are there issues in how cryptography is used in this short code sample?

I want to encrypt some small text files so I can put them online, in non-restricted access (not the best idea, but it's cheap and simple). I know I should use something like Truecrypt instead of this, ...
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247 views

Is AES S-Box resistant to side-channel attacks?

I know that implemntations with T-tables such as Golang's are prone to side-channel attacks, but is AES's S-Box wihtout any additional table also insecure ?
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Can someone help me understand this?

In the book Serious Cryptography It says for a cipher's permutation to be secure "Different keys should result in different permutations. Otherwise it becomes easier to decrypt without the key: ...
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Finding the relationship given by the generating elements of a non-abelian group (for a maximum case) where they correspond to finding cycles

Let $G=(\mathbb{Z}_p \times \mathbb{Z}_p) \rtimes_{\phi} \mathbb{Z}_q$, where $p$ and $q$ are odd distinct primes. Let $G$ be generated by the elements $s=(g_1,e_q)$ and $t=(e_p,g_3)$, $g_1,e_p \in \...
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Solving LPN using algorithm for syndrome decoding

Given an algorithm $A_D$ which solves an instance of the decoding problem $e \in \mathbb{F}_2^n$ in time $T_D$ given a parity check matrix $H \in \mathbb{F}_2^{(n-k)\times n}$ and a syndrome $s \in \...
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77 views

Anonymous key exchange protocol not secure vs. computationally unbounded adversary

Explain why an anonymous key exchange protocol cannot be secure against a computationally unbounded adversary.
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What is the difference between different corona tracing protocols?

At https://corona-tracing.org/ and https://www.cryptool.org/en/cto-highlights/corona-tracing an easy to understand way was presented how such contact tracing apps work from a cryptographical point ...

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