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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6
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1answer
699 views

Why is double encryption that's equivalent to single encryption no better than single encryption?

In the "Introduction to Cryptography: With Coding Theory" by Trappe and Washington, in the chapter about DES algorithm the authors say that: "if a cryptosystem is such that double encryption is ...
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0answers
23 views

Lineary of Sbox in DES

I'm not a mathematician, and i would like to understand in the most concise way (if possible) why choosing linear S-Box functions makes the DES algorithm attackable. Thanks
2
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1answer
36 views

Property of a good cipher system

In the "Introduction to Cryptography: With Coding Theory" by Trappe and Washington, in the chapter about DES algorithm the authors say that: "In a good cipher system, each bit of the ciphertext ...
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0answers
30 views

Finding the token [on hold]

I managed to decrypt the following message with vigenere but I did not manage to have the token at the end knowing that it contains 24 characters. Fkhuv djhqwv, Eudyr ! Yrv plvvlrqv rqw o'dlu gh vh ...
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0answers
27 views

Algorithms for solving systems of quadratic multivariate polynomials

What are the best algorithms for solving systems of $k$ polynomials equations where these are quadratic multivariate polynomials on $k$ variables? I've encountered such systems on my research and I'm ...
4
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2answers
74 views

Are there ready-to-use software that can try many decryption techniques on a ciphertext, with no information?

Let's say I receive a 1 MB encrypted file, but I get no information about the encryption method, and no password. The only thing I can guess is that the person probably used a weak encryption method ...
2
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0answers
59 views

Enhancing Differential-Linear Cryptanalysis

I'm studying Differential-Linear Cryptanalysis, and I'm trying to understand the context from the article Enhancing Differential-Linear Cryptanalysis by Eli Biham et al. There are some difficult ...
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1answer
47 views

One way secure DES key transfer to defend against attacker [closed]

I have a question about cryptanalysis. A transmit message to B with radio waves, A use modulator to transmit bytes with radio, B obviously use demodulator. A encrypts and B decrypts the messages ...
0
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1answer
41 views

How to break an unknown ciphertext - transposition of some kind [closed]

I've been challenged to crack a code. All I know about it is that is was hand-enciphered, and that it is a transposition cipher of some kind. When I was given it, I started plugging it into my ...
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0answers
23 views

How does this frequency matrix for the english language work? [closed]

I was reading a PDF (here) about using heuristic algorithms to break homophonic encryption, and came accross a graph generated with digram frequency analysis (section 2.2, table 1). Reading the ...
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2answers
39 views

Most efficient way to crack a monoalphabetic substitution cipher with spacing intact

I've got a cipher I've been challenged to crack by hand. It's a monoalphabetic substitution cipher, and the English spacing is intact, so all of the words are the right size. Is there a more ...
2
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1answer
58 views

Building Key Streams from PRNGs

I am reading an intro book about cryptography and the author tries to explain why using pseudo random number generators is vulnerable. Given PRNG equation; \begin{align} S_0 &= \text{seed}\\ S_{...
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37 views

In DES : Matsui's notation(LC) vs Biham's notation(DC)

I'm doing linear attack for 8 rounds DES. And I just wondering about the difference between matsui's notation and Biham's notation. In Matsui's paper, numbers bits from 0 to 63 from right to left. In ...
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1answer
156 views

Understanding LFSR stream ciphers and the content scrambling system

I'm a little confused over how exactly Linear Feedback Shift Registers (LFSR) work, I kind of get it, but not really, can someone help me understand it? I know it XORs bits in a loop against some mask,...
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0answers
32 views

Finding repeated groups of letters in the Kasiski examination

While doing the Kasiski examination I came to a problem. If there is the following group of letters in the cipher: AA and later on a group AAA is found. Does it count as two repeats or just one? And ...
1
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1answer
43 views

Attacks against RC4 when index $i$ is unknown

RC4 uses two 8-bit indices. One, $j$, is key-dependent and secret, and the other, $i$, increments by one for each byte output. The $i$ index is typically considered to be public, but what if the RC4 ...
4
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0answers
73 views

Parameters for high density SIS

I am considering the SIS problem of finding $x\in \mathbb{Z}^m$ such that for random $A\in\mathbb{Z}_q^{n\times m}$, $Ax=0$ and $\lVert x\rVert < \beta$ for some $p$-norm and bound $\beta < q$. ...
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0answers
33 views

Are slide attacks effective if the primitive is sandwiched? And key schedule vs. Even-Mansour

Suppose you have a cryptographic permutation consisting of identical rounds, that makes it vulnerable to a slide attack. But if you sandwich it between two XORs of key material. Is it still vulnerable?...
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0answers
61 views

Differential cryptanalysis filtering process

This question is a little more implementation based. I am writing my masters thesis on differential cryptanalysis and I wrote a program to evaluate some things about differential cryptanalysis. I ...
0
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0answers
30 views

Help, Feedback and Solutions to a problem on a PoC CSPRNG

Background I do not recommend trying to roll your own crypto. This is just a for-fun PoC, which won't be used in any public or private scenario. I am creating a PoC nearly-true random number ...
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0answers
29 views

How can I guess that a combination of Atbasch and Caesar / Vigenère has been used?

If I'm given a ciphertext, what kind of patterns, index of coincidence, frequency analysis would lead me to guess that it had been encrypted by a combination of Atbasch plus Caesar / Vigenère?
2
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1answer
117 views

Applications of machine learning in classical ciphers?

Machine learning is definitely applicable in analyzing simple shift ciphers like Caesar and affine ciphers, as well as substitution ciphers like Vigenère, but is it possible for machine learning to ...
0
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1answer
139 views

How are data science and cryptography related?

Are there any interesting connections between the fields of data science and cryptography? Data science involves the use of statistical analysis to analyze data while cryptography also involves ...
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1answer
70 views

How do discrete logarithm with modulo a prime and a non-prime compare?

Let $c_N = g^i \mod N$ and $N=p \cdot q$ and $c_P = f^j \mod P$ and $P$ a prime We assume $N,P$ has the same bit-length. $P$ is the best type of prime you can choose (e.g. safe prime). $N$ is a ...
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0answers
40 views

Constructing Differential Characteristics for Feistel Cipher

I have to construct for every i-round of Feistel cipher, for $i \in \{3,4,5,6,7,8\}$, a differential characteristic with there properties: $Pr[\Delta x = a \overset{f_i}{\rightarrow} \Delta y = b] = ...
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0answers
33 views

Guess the number of characteristics in differential cryptanalysis

I am doing some research on differential cryptanalysis for my master thesis. I analyzed some toy ciphers like the one in the popular tutorial about differential and linear cryptanalysis from heys Link....
17
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7answers
6k views

How to check a file was encrypted (really & correctly)

I would like to audit how an implementation of an encryption algorithm is really performed with the following given data of the problem: the encryption mechanism is reversible (this isn’t a signature)...
4
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1answer
53 views

Recover secret SHA-1 constants given Oracle

There's a black box that's basically SHA-1, except that the constants (h0, h1,...,h4) are secret. We can pass it arbitrary inputs and get the corresponding outputs. Given this, is it possible to ...
2
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0answers
84 views

A proposal for randomization of Niederreiter cryptosystem

The Niederreiter cryptosystem is a public key cryptosystem using Goppa code. Unfortunately it it is insecure unless it is a binary code. So I thought I could insert random linear codes into randomly ...
2
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2answers
193 views

Using AI to perform Cryptanalysis

If given a large set of examples of cyphertext and corresponding plaintext, could AI be trained to decrypt a cyphertext as the examples provided?, and if so, are there any examples online ...
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0answers
71 views

zero knowledge proof of range and set membership

I have a large number of items with a unique serial number and a score (score isn't always unique). There is a list which contains all of the serial numbers and their respective scores. I select 3 ...
13
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2answers
653 views

Is it safe to reuse a ECDSA nonce for two signatures if the public keys are different?

We denote the s value of an ECDSA signature $(r, s)$ on a message $m$ as: $s=\frac{H(m)+xr}{k}$ Assume two ECDSA signatures sharing the same nonce $(r, s_1) , (r, s_2)$ on two messages $m_1, m_2$, ...
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0answers
66 views

FPE current state of art for “small” domains

Is there any survey with the state of art treatment of format-preserving encryption for small domains (i.e. 2^20 for example)? I believe that Stalling's and Rogaway's surveys are out of date due to ...
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2answers
90 views

how can I test quality of sbox?

I have 11 sboxes, I want to test them and find the best one. How can I do that, I found several criterions for that but I could not understand.
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1answer
100 views

Are there any flaws in this pseudocode?

I'm developing an algorithm that cracks small RSA keys (And theoretically bigg ones too, though might take some time), and was wondering if anyone you spot any flaws in this python code: ...
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0answers
27 views

I'm studying about differential cryptanalysis in DES. I need to make the DDT through python [duplicate]

I just made DES algorithm(encryption, decryption) using python. And I want to attack 1,2 4,8 .. round DES. For that, I need to make the DDT code. Could you guys help me to make the DDT? Thank you.
3
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1answer
89 views

How can the Enigma's plugboard settings be found with partially known plaintext?

I don't quite understand the procedure described on wikipedia, is there a generalized procedure you can follow to rule out a pairing on the plugboard? For example, let's say the cipher text is ...
2
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0answers
94 views

Solving not so much overdetermined system of multivariate polynomial equations

I'm studying algorithms solving multivariate equations. I'm stuck in solving overdetermined set of quadratic equations. Concretely, with the number $n$ of variables, the number of equations is $m=\...
2
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1answer
79 views

Can the original data be extracted from an RSA private key signed message

I'm working on a system that the main objective is to verify the message was written by the right person, but it would also be desirable if the message can't be understood by anyone sniffing it. It ...
0
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1answer
32 views

Why do we approximate R-1 rounds during linear or differential cryptanalysis?

I am currently looking into differential and linear cryptanalysis. I am however unsure why do we only approximate only R-1 out of R rounds - is it because we already know the output or why ? I have ...
3
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1answer
35 views

Estimating difficulty of “Memory-Hard Proof-of-Work” based on “size of memory”?

In Bitcoin proof-of-work, the difficulty of Proof-of-Work is estimated and calculated based on total hashing power of the participants. If total hashing power of the participants is higher, then PoW ...
2
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0answers
88 views

Security of an Elliptic Curve Public Key with a “Small” x-coordinate

Consider an elliptic curve over a finite field $F_p$ with $p$ prime and order $n$. Let $Q$ be a generator for the field. Given a public key point $P = aQ$, suppose we have an algorithm that finds an ...
9
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1answer
4k views

How long does it take to crack RSA 1024 with a PC?

Using an Intel Core i5 CPU, how long does it take to crack RSA using a key size of 1024 bit (generated using a secure key pair generation function)? Suppose for instance that we have thousands of ...
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0answers
53 views

Implementation of differential cryptanalysis

This question is a little bit more implementation based of differential cryptanalysis. I hope it is okay. I am working with the book "The Block Cipher Companion" on the topic differential ...
2
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1answer
80 views

Differential cryptanalysis in “The Block Cipher Companion”

I am practically implementing a differential cryptanalysis on a cipher which can be found in the book "The Block Cipher Companion". Following image shows the cipher: In Fig. 6.10 (page 126) there are ...
28
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2answers
5k views

What are the implications of the new alleged key recovery attack preprint on SIMON?

Just recently, a new attack was published against SIMON-32/64 which claims to also be applicable to other versions of the cipher. The paper is titled A Note on SIMON-32/64 Security (archived 2019-05-...
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0answers
33 views

Why Diffusion and Confusion prevent statistical analysis? [duplicate]

I've studied the concepts of Diffusion and Confusion of cryptographic algorithms, however, I don't understand why they help in preventing a statistical analysis. Are you able to explain to me?
2
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1answer
59 views

How to determine if $\{n \cdot g^a \mod P\}$ and $\{m \cdot g^a \mod P\}$ generate the same sets? (set size < $P-1$)

given some examples $k_{n_i},k_{m_i}$ out of each value set: $k_{n_i} \in \{n \cdot g^a \mod P\, \forall a \in \mathbb{N}<P\}=G_m$ $k_{m_i} \in \{m \cdot g^a \mod P, \forall a \in \mathbb{N}<P\}...
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1answer
78 views

Is there a fast way to solve $k = n \cdot g^a \mod P$? (get $a$ for unknown $n$)

Would a factor besides the normal discrete logarithm problem increase or decrease the solving time? $k = n \cdot g^a \mod P$ with given $k,g,P$ and the knowledge $P= 2 \cdot N \cdot f+1$, while $...
3
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0answers
68 views

What is the probability equation of rotational cryptanalysis on modulo multiplication?

The answer in this question defined how to calculate the probability of rotational cryptanalysis on modulo multiplication $\odot$. This paper defined an algebraic equation of how to calculate the ...