Questions tagged [differential-analysis]

Differential cryptanalysis is a form of cryptanalysis which studies cryptographic algorithms by observing how differences in input affect differences on output.

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27
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How do I apply differential cryptanalysis to a block cipher?

I have read a lot of summaries of block ciphers particularly with regards to the NIST competitions stating that reduced-round block ciphers are – for example – vulnerable to differential cryptanalysis....
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Selection of rotation constants in ARX design

My question is about choosing the rotation values in ARX design such as SIMON-like or SPECK-like ciphers to provide optimal differential and linear immunity. According to this, the selection of $a$ ...
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Why is the permutation in AES (and other ciphers) not random or key-dependent?

If the permutation in AES (or other ciphers) were randomly generated or dependent on the key, would it not be stronger against differential attacks? If this is so, then might we need fewer rounds for ...
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573 views

Understanding the wide trail design strategy

I am trying to understand the wide trail design strategy. I have read the paper (paywall-free preprint) which describes it from the point of view of AES. From what I understand, it is a technique to ...
7
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2answers
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How to build a difference distribution table?

i am studying about differential cryptanalysis, and found one metric to measure the resistance of a sbox to it, but to use it, it is necessary to build a difference distribution table, like the one in ...
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Adding bit constants to the key schedule to reduce rounds?

Bit constants are often added to the key schedule to reduce slide attacks. I have reviewed David Wagner's work, where he showed that the increased rounds in a Feistel network do not help if you have ...
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Cryptanalysis and weaknesses of SEED cipher

I've discovered that a client has SEED enabled in their SSL ciphers, and would like to know a bit more about it from a security perspective. The Wikipedia article doesn't mention any flaws, yet I've ...
6
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1answer
409 views

What is a differential trail?

From what I could find it relates input differences to output differences usually across multiple rounds. But is it the entire probability distribution over all output differences for one input ...
6
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1answer
119 views

Differential and Linear trail propagation in Noekeon

In the Noekeon Cipher Specification they write the following : The propagation through Lambda is denoted by $(a \rightarrow A)$, also called a step. Because of the linearity of Lambda it is fully ...
6
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2answers
274 views

Can I use a differential that can be traced through the whole cipher with 100% probability?

I'm trying to attack a very simple cipher using differential cryptanalysis as a way of becoming familiar with this method. The cipher is so simple that I've found a differential which I can trace ...
6
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1answer
118 views

Finding differentials and space complexity

Most of article about differential cryptanalysis present the generic method, the way to find sub keys. But I can't find a clear explanation about how to find the differentials used in examples. In ...
5
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1answer
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Is TripleDES 168bit vulnerable to Differential Cryptanalysis?

I was reading this paper. In the table-1 of the paper it says TripleDES (showing both 128bit and 168bit keysize) is vulnerable to Differential Cryptanalysis. It also says that AES (showing all three ...
5
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1answer
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Difference between linear cryptanalysis and differential cryptanalysis

What is the main difference between linear cryptanalysis and differential cryptanalysis? For example in relation to DES?
5
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336 views

Security of the AES with a Secret S-box

In this paper they change the $AES$ S-box to a uniformly random one and answer the questions: How does the security of AES change when the S-box is changed by a secret S-box? Would it be safe to ...
5
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1answer
593 views

S-box with differential uniformity = 2

I read that we do not know if there exists an 8x8 sbox with differential uniformity = 2. I suppose we cannot compute every possible sbox because there are $64!$ possible s-boxes. Am I right?
5
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892 views

Differential cryptanalysis - breaking the last round of FEAL4?

I've been trying to learn cryptanalysis. I've come across this resource which proved very helpful: http://theamazingking.com/crypto-feal.php So far I've been almost successful in breaking FEAL4 ...
5
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1answer
509 views

Differential Cryptanalysis for Hash functions

How is differential cryptanalysis used to attack hash functions? I've been struggling through a couple academic papers and thesis's on the subject but they all sound like greek to me. Does anyone know ...
5
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633 views

What is the meaning of Maximum Expected Differential/Linear Probability (MEDP/MELP)?

I was reading this paper which has a lot of references to the terms MEDP and MELP. Even though i think i got the general meaning, I could not verify that it is indeed correct. For the MEDP, I would ...
5
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1answer
359 views

How is the SHA-1 collision detector so fast?

The google collision website shattered.it refers to a collision detector: https://github.com/cr-marcstevens/sha1collisiondetection. It claims a false positive rate of $2^{-90}$ and to take less then ...
5
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1answer
287 views

What is the difference between strong/weak alignment?

In this answer there is the mention of "weak alignment", followed by an indication that it is related to "resistance to truncated differential cryptanalysis". What exactly is the difference between ...
5
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1answer
280 views

differential cryptanalysis cipher for the final round

I have a problem to find the sub-key. The system is… For each round, we make the following stage: We add the round key $K_i$. Substitution : we have 8 blocks of 4 bits, and an S-box ...
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Is the difference distribution table of AES S-box uniform?

I am studying about various block ciphers and their weaknesses, so I have a doubt about AES S-boxes, Is the difference distribution table of AES uniform ?
4
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2answers
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DES with the bitwise complement of a key

I was reading upon Biham and Shamir's paper and a fact has been presented over there: if $ P_1 = \bar P_2$ and I choose a key $K_1 = \bar K_2$ then in that case $$T_1 = DES(P_1, K_1)$$ $$T_2 = DES(...
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1answer
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Best differential characteristic for this PRF

Consider the following construction of a PRF $F: \{0,1\}^{128} \times \{0,1\}^{64} \to \{0,1\}^{64}$ on 64-bit messages and 128-bit keys. Define $f:\{0,1\}^3 \to \{0,1\}$ by $$f(c,x,y) = \begin{...
4
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1answer
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Cryptanalysis of MD4 (Wang et al) — how did the authors come up with the collision differential?

Edit: ok, after I re-read the paper a couple of times it is clear that Table 6 is easily derived from Table 5, which describes the collision differential. So the real question is: how did the ...
4
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1answer
187 views

it is possible to use quantum algorithm search (Grover's algorithm) for new searching strategies for differential and linear attacks

I am trying to use Grover's algorithm to find Differential characteristic of Feistel and SPN structures block ciphers. basically, which is Finding a good differential characteristic with high ...
3
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2answers
969 views

Two-dimensional S-Box

Consider the following simple cipher: $$c_1 = S(m_1 \oplus k_1) \oplus k_2$$ Where $S$ is S-box, $m_1$ - 16-bit plain text, $k_1$ and $k_2$ is two parts of 16-bit key. If S-box is standard then this ...
3
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1answer
621 views

How to prove a cipher resistant to differential cryptanalysis?

How do you prove that a cipher is resistant to differential cryptanalysis? It's said that Rijndael has been proven resistance to differential cryptanalysis. How do cryptographers do that?
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1answer
363 views

Performing differential cryptanalysis for randomly generated S-boxes

As far as I know, performing differential or linear cryptanalysis always requires a knowledge of the S-boxes' content and order. Yet in Bruce Schneier's Applied Cryptography, it is stated that random ...
3
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2answers
565 views

differential and linear cryptanalysis

I have been reading about differential and linear cryptanalysis. They were mainly introduced by Adi Shamir and Biham to show weakness of DES. However, many of articles state that they have been ...
3
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1answer
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What does it mean : “Canonical representative of Sbox is 0123468A5BCF79DE”? and How can we calculate this representative for Sbox?

In paper :Cryptographic Analysis of All 4 × 4-Bit S-Boxes Saarinen has classified $4 \times 4$ S-Boxes and defined Canonical representative for each class of S-Boxes. What does "Canonical ...
3
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1answer
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Why is variable rotation uncommon in cryptographic primitives?

Most cryptographic primitives I've seen rotate by a constant. RC5 did something different though: For a word size $w=2^n$, you can take the last $n$ bits of a value as a rotation amount. There's more ...
3
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2answers
455 views

How do we find the subkey out of a differential cryptanalysis?

I understand the differential cryptanalysis up to the "finding the last subkey" part. If XORing with the key doesn't change the differentials, how can testing different key affect the equations we ...
3
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1answer
171 views

Minimum number of active s box to be resistance to differential cryptanalysis

I am calculating the minimum number of active s_boxes for block cipher using mixed integer programming, when can we say that block cipher is resistance to differential cryptanalysis after which round? ...
3
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1answer
235 views

Differential & linear characteristics for integer multiplication

What are the probabilities of differential & linear characteristics for the function that XORs the high and low bits from a $n \times n \rightarrow 2n$ bit multiplication? I remember reading ...
3
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1answer
155 views

Differential cryptanalysis tutorial of Howard M. Heys

I am currently working on some research about differential cryptanalysis. There is a lot of literature about that topic in the internet. One of the most known paper is the tutorial on linear and ...
3
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1answer
165 views

Countering Cryptographic Attacks

By reading Camellia Design and Analysis document following is my understanding about few cryptographic attacks from designer point of view. Differential and Linear Crypt-analysis. Number of Active S-...
3
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1answer
168 views

Differential bound of the S-Box in GOST R34.11-2012

In Russian GOST R34.11-2012 LPS-transformation is used. LPS gets all of its non-linearity from the 8-bit S-box S, which apparently has been designed to offer resistance against classical methods of ...
3
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0answers
63 views

Does this approach on MEDP take into account the multiple differential trails?

I was reading this (chapter 3.1) paper, and the author proposed this method to calculate the MEDP on 2-round AES: I cannot fully understand what he is doing but it seems like it iterating over all ...
2
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3answers
835 views

What is the point of differential cryptanalysis when the amount of necessary plaintext is unrealistic?

As someone with a non-crypto background, I learned that differential cryptanalysis is mostly weak against ciphers like DES because, being a chosen plaintext attack, for a state of art complexity of $2^...
2
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1answer
654 views

How can one construct the weakest S-box ever?

Is it possible to come up with an NxN S-box which would have a difference distribution table with N entries of 100% probability? I am studying the properties of S-boxes and I don't quite understand ...
2
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1answer
681 views

Differential Fault Analysis of AES

Let's say: an error is induced into an implementation of the AES-128 to produce a faulty ciphertext. The error is a one-byte eror and is always induced on the last state byte, during round9, before ...
2
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1answer
400 views

What is an advantage of MDS matrices in block ciphers?

I saw the several articles about MDS matrices. They said that, one goal of MDS matrices is to protect the block ciphers against linear and differential attacks. My question is: For example in the ...
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1answer
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What is the complexity for attacking 3DES in linear or differential cryptanalysis?

I know that 3DES is NOT vulnerable to DC , LC . But is it because the attacks requires too many input\output pairs ? Or because it's impossible ? (i.e requires more than 2^64 pair )
2
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1answer
288 views

SHA-1 collision resistance

I'm researching on the SHA-1 algorithm and looking for reasons why it has fallen prey to differential cryptanalysis. I have read the research papers by Merc Stevens and Wang both of which describe how ...
2
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2answers
212 views

How does linear vs. non-linear operations relate to cryptographic security and differential cryptanalysis?

I understand what a linear operation is and what a non-linear operation is, but I would like an explanation of specifically how a non-linear operation on input data mitigates differential crytanalysis ...
2
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1answer
73 views

The Collision Differential for MD4 - a question on notation (Wang, et al)

In the paper "Cryptanalysis of the Hash Functions MD4 and RIPEMD" the authors introduce the following notation (paragraph 4.1): $\Delta$$H_0$ = 0 $\xrightarrow{(M_,M')}$ $\Delta$$H$ = 0 What exactly ...
2
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1answer
165 views

Are SHA-2's $\mathit{Maj}$ and $\mathit{Ch}$ functions non-linear?

SHA-2 has two functions: $\mathit{Maj}(x, y, z) = (x \land y) \oplus (y \land z) \oplus (x \land z)$ $\mathit{Ch}(x, y, z) = (x \land y) \lor (\neg x \land z)$ Are these two functions non-linear? ...
2
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1answer
238 views

Differential or Truncated Differential Attack On Small Cipher

The cipher given below is a 16-bit toy cipher which uses 8-bit sbox and 2x2 byte Matrix. The Key $k_0$ and $k_1$ are $\oplus$ with the data. The multiplication with matrix is performed in $GF(2^8)$ ...
2
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1answer
87 views

Symmetric property of DDT of inverse function

Given a bijective function $F: \mathbb{F}_2^n \rightarrow \mathbb{F}_2^n$. The entry of the Difference Distribution Table (DDT) at row $\alpha$ and column $\beta$ is defined as $$DDT_{F}(\alpha,\...