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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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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Vigenere cipher probabilities

Consider the Vigenere cipher over the lowercase English alphabet, where the key can have length 1 or length 2, each with 50% probability. Say the distribution over plaintexts is $\Pr[M=\text{aa}] = 0....
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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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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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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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Attacks on LCG with “self-XOR” output function?

Consider an ordinary LCG modulo $2^n$ with an internal state of $n$ bits and an output of $n/2$ bits, with the twist that instead of simply truncating the state to produce an output, we take the upper ...
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How does breaking AES with a side channel attack (CPA) differ from a side channel attack on something like a microcontroller?

I'm studying CPA side channel attacks. CPA stands for Correlation Power analysis and it can be used to break AES. I'm familiar with the process to crack AES on a microcontroller. I was just wondering ...
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How to determine the security of a HASH system?

I am having trouble answering the following questions, I am extremely new to cryptography: When determining the security of a HASH system, the cryptanalyst tries the following attacks. (a) If the ...
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would this be classed as a cipher text attack?

Say i'm given a cipher text to decrypt, however i also have access to a server that performed the encryption; where i could enter any plaintext and observe the result of encryption. would it be ...
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Hash function without avalanche effect but with few collisions

I am searching for a hash function which has these attributes: low Avalanche Effect, similiar files should get similiar outputs low number of collisions (if I have 0*10000 in one file, and 0*99999 + ...
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Size of messages in timing attack on RSA Montgomery

I'm codin' timing attack on RSA Montgomery which compares two sets ( the first one includes those which need a reduction in contrary to the second one ). But I got troubles with the Montgomery ...
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AES ECB deterministic encryption to perform Private set intersection

There are two parties, and each has a list of plain-texts. My end goal is to assign indices to unique plain-texts across both parties. My present approach is the following. Both parties perform a ...
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Canonical inclusion map in subfield attack on overstretched NTRU

I'm trying to understand subfield attacks on overstretched NTRU. In the paper https://eprint.iacr.org/2016/127.pdf authors used "canonical inclusion map" to lift vector to full lattice. What does ...
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Can someone explain the timing attack on RSA with Montgomery multiplication?

I have read several articles on the temporal attack against Montgomery multiplication to speedup RSA computations. However, I do not quite get the principle. I understood that there is a additional ...
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Is it possible to predict a randomly generated BigInteger that uses Java's default Random library?

I've seen it posted on different forms here and here that explain how java.util.Random library uses a linear congruential pseudorandom number generator which can be ...
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Is there any appropriate way to break a specific S-BOX?

I have just started learning cryptography. And I came across such a question that had troubled me for several days. The picture contains an LFSR and an S-Box. The LFSR is 32-bit long and the inside ...
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Rivest - Time Memory Tradeoff Using Distinguished Points

A while ago, Hellman introduced a time-memory tradeoff for chosen plaintext attack on block ciphers. There is an innovation due Rivest using a concept of 'distinguished points'. I am looking for the ...
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What is the current security level of an algorithm?

I was reading a paper of some years ago about a cryptography and a phrase got my attention. We want to ensure a security level of at least $2^{80}$ I know that $2^{80}$ was used as rule of thumb ...
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Cryptanalysis of a feedback shift reigister with an S-box

I’m just getting started on learning cryptography and here is a problem from exercises about which I'm totally confused: This is a 32-bit feedback shift register to encrypt some message. The register ...
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Excluding specific factors for Pohlig-Hellman

I want to use Pohlig-Hellman and BSGS to solve the discrete log of an Elliptic Curve which has a composite order generator. The ...
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Is there any way to find out two numbers such that the XOR between them is a given number?

I have the following operation I took from a cryptanalysis I'm performing for a specific CBC encryption where the challenger has provided the key: ...
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how to predict a sequence for reverse engineering of a ticketing system [closed]

i am student in the fith year of college IT-science and a crypto noob. i have been wondering how the folwing sequence of ticket i bougth in all at once were built for : how they work or how they are ...
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Nonce of AES-GCM generated by Counters

i am trying to generate the nonce for AES-GCM. I know people usually generate it by Counters and LFSRs. I am confused about the meaning of Counters. Is that means Counter (CTR)? Why it can generate ...
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Boolean cube in Cube attack

The following doubts are from Chapter 3 of the following resource: ResearchGate Cube Attack. Could somebody elaborate on how to find the right-hand side of the superpoly? In this, the degree is ...
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What is the exact algorithm for encryption and decryption with hummingbird-1 cryptography?

I have really googled the entire internet but could not find a clear algorithm for hummingbird-1 cryptography.The problem emerges in the decryption module: What is the initial value of state register ...
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Related-key impossible differential search on SIMECK via MILP?

What should be the objective function , constraints and bounds for the model for Related-key impossible differential search on simeck cipher using mixed integer linear programming (MILP)?
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Unknown bit in the output of encryption of data using SIMECK32 cipher?

How is the unknown bits (annotated by red arrow in figure below) come in the OUTPUT after round 1 and round 2 ? Following is the pictorial representation of SIMECK round function operation. Ref: ...
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How to calculate the redundancy of a language

I originally asked this question on the information security stack exchange but I think it's better suited here. I'm trying to calculating the unicity distance for a cipher applied to a language I ...
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Symmetric versus asymmetric self encryption

I can encrypt my files with a symmetric encryption algorithm like AES, or with an asymmetric encryption algorithm like RSA or ECC (I encrypt my files with my own public key). No communication is ...
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Estimating the probability of success of a Turing-Welchman attack on an enigma machine as a function of the length of the crib (known plaintext)?

Could anyone please tell me how to to Estimate the probability of success of a Turing-Welchman attack as a function of the length of a crib (known plaintext)?? for example we have the : plain text=...
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Classification of attacks against lattices

I'm interested about the cryptanalysis side of lattice-based cryptography, and was wondering whether there is a survey paper or something that gives some classification of attacks against lattices, ...
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Relationship between $N$ and $\phi(N)$ in the RSA algorithm

Recently I started learning how the RSA algorithm works and there is one single part of the computation which really confuses me and can't get over it. Let's say I chose 2 prime numbers, namely $P ...
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Are there any state of the art crypanalysis tools for stream cipher

I am new to cryptanalysis and interested in knowing cryptanalysis tools (black boxing or white boxing) for (not any specific) stream ciphers in general sense. Scenario: I am given an assignment to ...
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Dieharder input file with a sequence of only binary numbers

I have a RNG producing sequences of binary numbers, ad I would like to run Dieharder test using them as an ascii txt input file. However I haven't been able to do it properly. Should I use a header ...
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Use large key size for RC4 to avoid RC4 bias

I saw a question on StackOverflow where RC4 was initialized by a 1024 bit key (with 2048 the maximum key size, if I'm not mistaken). Will such a large key size possibly solve any of the bias of the ...
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Insecure MAC built on pseudorandom function

this is a question about Katz-Lindell book, introduction to modern cryptography, 2nd edition, exercise 4.7, part c. For (a) and (b) it is clear that the Macs are insecure, but for (c) I am struggling ...
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Help on Algebraic Side Channel Attacks

I am a master student in computer security, I am preparing a dissertation thesis in the theme is: Algebraic cryptanalys by auxiliary channels, I need reference on this theme (book, thesis, ...), and ...
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Is there any practical use of reduced rounds of AES

There are lots of attacks which are on reduced block ciphers. There are practical attack on five rounds of AES-128five rounds aes broken in six minutes. I was just wondering if there is any practical ...
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Can zkSNARK or other zero-knowledge proofs be used to proof message authenticity without revealing private key?

The situation: Alice and Bob are exchanging messages encrypted by some known asymmetric encryption protocol. All their encrypted messages, as well as public keys are intercepted by Charlie. Can ...
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Factorization problem

Say, $X= a\cdot b$, where $(a, b) \in Z_q^*$ and $q$ is a large prime. If $X$ is given, then what is the complexity (or hardness) of finding $a$ and $b$? Note that, either $a$ or $b$ can be reused to ...
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Correlation power analysis attack on Camellia

I'm investigating a correlation power analysis on a black-box ASIC I have. I want to learn about correlation analysis and it seems this ASIC implements Camellia. I searched for researches that did ...
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18 rounds encryption in embedded?

I have a power trace of a decryption. It seems like I'm watching a 18 rounds decryption algorithm. I cannot think about any other algorithm implemented in ASIC except Cammelia who has 18 rounds. ...
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How to find a small generator with small inverse? Does it have negative impact to security? (for Schnorr subgroup of $\mathbb{Z}/P\mathbb{Z}$)

Given a prime $P$ with $$P= r \cdot q+1$$ with $q$ prime as well. I'm looking for a generator $g$ of the Schnorr subgroup with order $q$ which is small by value and has a inverse (to $\bmod P$) which ...
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What are the security implications of knowing the private polynomial $\mathcal{F}$

First, affine transformations $S,T$ are defined by $S=A_1+v_s, T=A_2+v_t$. Let the private polynomial function $\mathcal{F}$ be known. The short description of the public key map is $P(X) = T \circ \...
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Is there a feasible way to reconstruct the key from the (Triple-)DES round key?

Assume there is a closed source application which uses Triple-DES with a fixed/hardcoded key to decrypt large amounts of data. Someone managed to extract the round keys from a process memory dump and ...
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Which is the smallest safe elliptic curve (bit-length)?

At https://safecurves.cr.yp.to/ some elliptic curves are listed which passed certain security test. The smallest bit-length of a safe curve listed there is 221 bits. At wiki page discrete logarithm ...
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How do I calculate the conditional probability of a Caesar cipher?

I have a frequency distribution of letters for the plaintext and the ciphertext. I'm trying to determine the conditional probabilities to identify the plaintext/ciphertext pairings. If I encrypt ...
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Differential cryptanalysis of FEAL-4 recovering last subkeys

I am familiar with the differential cryptanalysis of small SPN-based ciphers like here: Tutorial of Amazing King with SPN (or mentioned in the book "The Block Cipher Companion" or the Tutorial of ...
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Breaking RC5 without rotations

I'm trying to follow Schneier's self-study course in cryptanalysis and am ashamed to say I am stuck on the very first problem of breaking 8-round RC5 without any rotations (i.e. just XOR and modular ...
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Help with cryptanalysis of branching in schemes based on Multivariate Public Key Cryptography

I'm familiarized with the structure of branching found in Multivariate Cryptography, as it allows us to partition a $n$-tuple over $F_{q}$ into a $k$-tuple where the $i$-th element is in $F_{q^{\...

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