# 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”).

185 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
393 views

### Finding generator element for multiplicative group of order $n$ - feasible?

Given a multiplicative group of order $n$, how hard is it to find a generator element (such that all other elements can be expressed as powers of that generator)? What would be the complexity?
77 views

### Question on nCPA Security and Uniform Permutations

I feel I am misunderstanding the idea of nCPA security and its relation to uniform permutations. In particular I've been reading the paper "Hoang, Morris Rogaway; An Enciphering Scheme Based on a Card ...
130 views

### Mersenne Twister's vulnerabilty with small-size distributions

C++ rookie here, trying to wrap his head around (CS)PRNGs. I (assume that I) already understand the concept of the Mersenne Twister being "broken" (i.e. not cryptographically secure) due to its ...
51 views

### Preserving location privacy

What are cryptographic techniques that could be used so that if I wanna to enable a server to send message to certain nodes in a network with preserving the privacy location for them ??
451 views

### Cryptanalysis affine cipher and substitution cipher

1) Consider the chosen-plaintext attack on the simple substitution cipher. How many chosen plaintext characters suffice to uniquely determine the key? My answer was: 26! 2) Consider the chosen-...
149 views

### Leak information (new setting)

This question is similar to Leak Information?, but with new settings. Let $a,b,c,d,e,f$ be selected at random from $\mathbb Z^*_q$. Also, let $r_1,r_2,r_3,z_1,z_2,z_3,p_1,p_2,p_3$ be selected at ...
67 views

### Can I deduce the info such as the bitsize of an LFSR from multiple ciphertext messages?

If I encrypt the same message multiple times (>10000 times) with the same LFSR can I then somehow retrieve some information on the LFSR? I'm looking for information like bit size, polynomial used. The ...
81 views

### What is the attack complexity if two stream ciphers are connected in cascade?

What is the attack complexity when Grain-128 and Trivium are cascaded? Is it 2^(256 + 128) since internal state of Grain is 256 bits and assuming that IV is unknown before encryption?
68 views

### A name for “word fingerprints” (technique for breaking monoalphabetic substitutional ciphers)

I have invented a technique for breaking monoalphabetic substitution ciphers. However, I believe that such simple thing must have been already invented. I wonder how is this called. I call it “word ...
1k views

### RC4: Find the complete plain text of a ciphertext when we know part of the plaintext

I need to decrypt an encrypted file with RC4 to answer to a Internet challenge. The file in question is a dump of a Teensy ROM and it is completely encrypted. Luckily, it looks like it's a standard ...
54 views

### What weak symmetric cryptographic algorithms shall I use to educate myself about cryptoanalysis methods?

Are there any simple to understand and implement, but nontrivial cyphers and hash functions which are easily broken by modern cryptoanalysis methods (for example, ones listed in Wikipedia)? Ideally ...
736 views

197 views

### RSA OAEP: prevention of partial decryption of ciphertexts

I'm trying to understand RSA encryption (as a beginner in cryptography). go on this wiki page http://en.wikipedia.org/wiki/Optimal_asymmetric_encryption_padding scroll down to the 2 numbered points: "...
98 views

### To prove $r_2$ is a uniformly at random value in $Z_n$, where $r_2=r_1 . m$

$m$ is arbitrary value in $Z_n$, where n is RSA modulo. Then we do: $r_2=r_1 . m (modn)$, where $r_1$ is a random value such that $r_1\in Z^*_n$. ** Question(1): is $r_2$ a uniformly at random ...
25 views

### Cryptography — with a semi-priveleged user in the middle — to prevent request-tampering with another server

I'm working on a chat server for a mobile app I am writing. I would like to use a different application server for non-chat related operations and another application for chat operations. I would ...
45 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 ...
63 views

### 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 ...
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 ...
32 views

### 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 ...
17 views

### 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 ...
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 ...
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 ...
28 views

### How to find Difference distribution table of DES S box?

I Have used Sage command ...
20 views

### I was going through Path ORAM in oblivious RAM. I found it very interesting, as its promising but is there any scope left to enhance it?

Is there any specific field in Path ORAM where I can further investigate or research?
31 views

### How do I model this system?

I was trying to work out the security of an system that used the polarized LCD panel over an OLED display (the point being that you can only block certain pixels) and the pixels are either on or off (...
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
38 views

### Identify encryption scheme - Many-To-One?

What type of encryption is used when the encrypted phrase only uses the letters from a keyword? For Example: Keyword: Stack tkc ska ktkkac skccaasca ckssak This was encrypted using only the letters ...
23 views

### Fundamentals of XL algorithm

I am trying to understand XL algorithm and F4/F5 algorithms for solving multivariate polynomial systems. Is XL related to the Grobner basis? I would be grateful if anyone could suggest me the topics (...
87 views

### One-time pad: Using Cribdrag for Decipherment and Key Recovery

I have been given three different strings: ...
46 views

### Reversing black box algorithm

I'm trying to solve the next problem: We have X - input vector, its length is 128 bits. Output vector Y, its length 2048 bits. ...
27 views

### Is there a LPN estimator like LWE?

I recently studied the LPN problem and BKW algorithm for solving LPN problem. Several papers deal with the concrete parameters of LPN to be secure against BKW algorithm, but I cannot measure the ...