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 does cryptanalysis of the Playfair cipher work?

I have a set of Playfair-enciphered data that I'm trying to crack without the key. I know I need to analyse bigrams; I've currently worked out what decrypts to th, <...
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1answer
79 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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1answer
56 views

How does the frequency work with Vigenère Cipher?

So I have an unknown key but with the length of 6. I understand that I calculate my own English letter frequency of my letters. I then compare it with the standard English letter frequency and ...
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Definition of textbook RSA

What is the definition of textbook or "raw" RSA? What are some of the properties of textbook RSA? How does it differ from other schemes based on RSA?
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Which contemporary programming language is apt for implementation of algorithms in cryptography?

I am a researcher in cryptography. Most of the time I generally do theoretical/Mathematical work only and not doing the implementation part. I am not able to get the feel about the time complexity of ...
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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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42 views

ε-close to t-wise inependence of SPN (AES)

According to theorem 3.13, the 6 rounds of AES is 0.472-close to pairwise independence. It is also mentioned t-wise independence used to analyze higher order derivates attacks. it is also mentioned 3-...
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4answers
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Modifying an Enigma machine to allow unchanged letters

One of the biggest flaws of Enigma was that a letter couldn’t represent itself because the route through the machine was one-way. I was thinking a quick fix could be to introduce a rotor position that ...
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98 views

Method for cryptanalysis of a keyword-keyletter cipher?

I am a CS student who is in an introductory cryptography course. I am not looking for the complete plaintext of this message, as I am not looking to cheat. I am simply stuck and have no idea what to ...
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1answer
453 views

What does “adaptively secure” mean?

In a paper it says "In the generic group model, the PRF is adaptively secure for inputs of $\mathbb{Z}_q^n$". Maybe a stupid question, but what does "adaptively secure" mean exactly?
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Profile Complexity of an LFSR

I am trying to understand how the linear complexity profile of an LFSR is calculated. For example, I have the bit sequence $110101$ and its profile $1 1 2 2 3 3$. Is there any easy way to produce the ...
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1answer
87 views

Mixing Autokey with Regular Vigenère

It seems to me that cryptanalysis of the autokey cipher relies on patterns being found in key attempts, easy when it's English you're looking for, but how can you do this if you're just getting ...
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4answers
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Is Wiener's attack on RSA extendable to larger keys with low hamming weight?

Using small private exponents with RSA improves performance. However, it has been shown (Wiener, 1990) that if $\log d \leq \frac14 \log N$, the private exponent $d$ can be reconstructed from the ...
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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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1answer
534 views

Cracking a key using a combination of partial keys

As part of a cryptanalytic attack I've carried out, I used a divide-and-conquer strategy to divide the secret key $k$ into several equal-sized partial keys $k = {k_1, k_2, ...}$. The attack works ...
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1answer
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What vulnerabilities does the LFSR filter generator have?

As the title suggests, I wonder what kinds of attacks there are in the LFSR filter generator. The most representative attack is the fast correlation attack and inversion attack. I wonder what other ...
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2answers
125 views

Does SHA-256 have (128-time + 128-space = 256-overall)-bit collision resistance?

First, we consider those hash functions that can actually provide 256-bit pre-image security, and not something like SHAKE128<l=256bits> where the sponge ...
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1answer
190 views

Does this paper find cryptographic weakness of SHA-256?

I found only the abstract and tables of this paper https://dl.acm.org/doi/abs/10.1145/3409501.3409513 From the abstract In this paper, the researchers proved that the modified SHA256 is viable to ...
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1answer
35 views

CrypTool RSA Features [duplicate]

I am attempting to manually encrypt a plaintext message (message = MI) using RSA. I receive an answer of: 33,264 and 21,164. When I enter the same plaintext into CrypTool to confirm that my ...
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2answers
272 views

Examples of Weak Cryptography being exploited in the wild by cybercriminals?

As a theorist, I often motivate the need for strong cryptography via simplistic methods, such as "If this did not exist, your online bank transactions would be vulnerable". This is of course ...
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7answers
99k views

Taking advantage of one-time pad key reuse?

Suppose Alice wants to send encryptions (under a one-time pad) of $m_1$ and $m_2$ to Bob over a public channel. Alice and Bob have a shared key $k$; however, both messages are the same length as the ...
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28 views

A few questions regarding the 4-Round AES-Distinguisher (by Gilbert and Minier) and DS-MITM

I am struggling to understand the DS-MITM attack on AES (Original Paper). Especially the 4-rounds distinguisher by Gilbert and Minier (section 3). I get the basic idea that we check exactly on which ...
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1answer
176 views

Security analysis for a extended ElGamal Signature against selective unforgeability

Let $H$ is a cryptography hash function and $\Pi=(\mathsf{G}, \mathsf{S}, \mathsf{V})$ is a digital signature, as follows: $(h_1=g^x,h_2=g^y) \leftarrow \mathsf{G}(1^n)$, where $x,y$ uniformly ...
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1answer
77 views

Why is this DES key considered weak?

I understand the premise of weak keys in DES and cryptography. From searching online, I understand that keys that are comprised of all zeroes / all ones / alternating ones and zeroes / alternating ...
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Decrypt encryptedKey session key using - AES-128 - PKCS-1#rsaes-kem-kdf2-kw-aes128

I have basic knowledge about how encryption algorithms work such as RSA, AES and so on. I have an XML response encrypted with both AES and RSA. I tried using OpenSSL to decrypt with several steps but ...
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0answers
31 views

Differential cryptanalysis to ciphertext-only attacks on xxTEA

In my IOT project, I use the xxTEA encryption algorithm to encrypt my data. I use the same encryption key for all my packets because I don't have the possibility to do a key exchange between Alice and ...
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Need some help with decryption code for monoalphabetic substitution

I am working on decrypting ciphertext in monoalphabetic substitution algorithm. I tried to decrypt using frequency histogram of english alphabets individually. The percentage of these frequencies are ...
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0answers
60 views

Howgrave-Graham lattice attack on NTRU

I am lookin for a good example to illustrate this attack on NTRU using low parameters but I failed to do that, The attack consist to use LLL reduction on A basis of NTRU Lattice, let us use the column ...
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1answer
64 views

Is a Test Vector feature a Security Hole?

I have a system where a block cipher key (likely AES) is entered via a 'command line' over a serial console, probably as hex. The system has no 'print key' feature, so the key is hopefully 'ingest ...
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1answer
67 views

Complexity of Boomerang Attack on COCONUT98

I am trying to understand the paper The Boomerang Attack from David Wagner. On page 162 about complexity of boomerang attack the paper says that: The attack requires $8 \cdot 2 \cdot 32 \cdot 2^{32} ...
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1answer
152 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
510 views

help with cryptanalysis of a sponge permutation

I have been studying and researching hash functions. So far my research has led me to the sponge construction. It appears that the permutation used in the sponge to stir the state is more or less ...
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How does a forward search attack work? [duplicate]

I just came across this term “forward search attack” while reading about Interchange key and Session key. The book mentioned that using session key helps to prevent attacks such as forward search ...
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1answer
101 views

Verify that a point belongs to secp256r1

I need to verify that the point in this public key ...
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1answer
44 views

Nonlinearity of a Boolean function with odd number of input bits

Highly nonlinear functions are used in combination generators and other stream ciphers. We know that maximum nonlinearity (hamming distance to all affine functions) of $f$ is achieved when $f$ is bent ...
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1answer
47 views

How to determine secp256r1 or secp256k1 is used on the web sites

I'm pretty new at Cryptography (and at Cryptanalysis), but I went to the website Elliptic to try to discover the elliptic curve they use, and I found they use ECDP 256. So, by SEC2 I discovered they ...
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1answer
32 views

Quadratic Equations to Describe SBox

I am using a 8 bit Sbox having 16 entries with a lookup table of 4x4 in cryptographic algorithm. Sbox is constructed on subgroup of galois field 2^8. I want to calculate number of quadratic equations ...
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2answers
52 views

Does the diffie helman rachet in double ratchet do anything if one side never replies?

I am a little confused on how this functions so apologies in advance if the question is naive. The way i understand it, the function of the standard sending and receiving ratchets in Double Ratchet is ...
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1answer
197 views

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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Few questions about setting up SuperCop primitives

Have a couple of questions about the supercop library. I've refrained from asking this question for a considerable amount of time because every time I thought about asking it, it sounded stupid in my ...
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54 views

Cryptographic Principles: Bit-Flipping Attack

I'm working and reading about bit-flipping attack and how to set it up. I just got a question, which I am not sure, how I should answer. Question: 'Why is this easy with a stream cipher but not ...
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2answers
116 views

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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Comparison of SNARK-friendly hash algorithms MiMC7, Poseidon, Pederson?

There are some cryptographically secure hash algorithms designed to be efficient for SNARKs, STARKs and FHE. Some of them already implemented in Zcash, Zokrates and circom. The ones that I know of are:...
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1answer
35 views

Paillier estimate attack costs on short keys

I was thinking about how to use the homeomorphic property of that cryptosystem to achieve not a "semantic security" but a less ambitous obfuscation of the source code (an ipotetical scenario ...
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1answer
99 views

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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35 views

Difficult to guess the targeted receiver

The protocol is defined as : Bob want to send message to one of his friends say $k$ friends , he does not want his others friends (except one whom he want to send message ) to tell who is targeted ...
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28 views

How to find Difference distribution table of DES S box?

I Have used Sage command ...
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1answer
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Can Big Data together with deep neural networks attack RSA by affording the vast calculation of prime multiplications in advance?

This is a spin-off from Can Big Data attack RSA by just calculating many prime multiplications in advance? [duplicate]. Intro I am somewhat new to cryptography. Repeating the basics of RSA from How ...
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1answer
59 views

In the reduction proof below, where OWF exists only if is a PRG. I am not able to understand the highlighted part

I am able to understand how G(x) id generated. But then what is the use of variable z. Also if the probability is >1/2 + e then the distinguisher wins! Then how is this still a OWF

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