analysing cryptographic algorithms, potentially uncovering weaknesses in them (e.g. "breaking" them or casting doubts on their actual security)

learn more… | top users | synonyms

0
votes
0answers
20 views

What are the links between Cryptography and Algebraic Topology?

I have asked "What are application of Cryptography in Algebraic Topology". But I want to know whether are there any relation between Algebraic Topology and Cryptography. Are there any application of ...
1
vote
0answers
98 views

Is chaotic encryption secure?

I know this sounds too broad. But I noticed that there was a chapter on chaotic crypto in the recent Handbook of Information and Communication Security Editors: Stavroulakis, Peter, Stamp, Mark (Eds.) ...
1
vote
1answer
43 views

Vigenère, auto-correlation vs Kasiski examination

What are the differences between 'Kasiski examination' and 'auto-correlation' ? In Cryptool site, they state that autocorrelation analysis is more efficient and clearer than the Friedman or Kasiski ...
10
votes
3answers
612 views

How Brittle Are LCG-Cracking Techniques?

There are published techniques for cracking LCGs, but to my eye those techniques seem very brittle — very minor changes can add nonlinearity that renders techniques like the LLL algorithm unusable. ...
-3
votes
0answers
50 views

Is there any method to avoid the differential cryptanalysis? [on hold]

May I know the Best ways to avoid the Differential Attack in block cipher algorithms (AES,Speck,Simon etc). The probability of differential cryptanalysis is achieved mostly equal to 1 in speck light ...
0
votes
0answers
25 views

Security for multiple functions for a functional encryption scheme

Assuming a functional encryption scheme $F$ in which an untrusted server is able to learn the sum, the multiplication and the sum of the inverses of an $n$ dimensional vector $x \in \mathbb{F}_N^*$ ...
2
votes
1answer
74 views

RFID Protocol Cryptanalysis

Assume we have the following scheme for RFID: TAG & READER both have initially k keys. Every session the TAG computes $k_i$=F($k_{i-1})$ where F is a function which computes XOR of previous key ...
-3
votes
0answers
55 views

Question about feistel network [on hold]

What’s the output of two round Feistel network, 1) when input is 1^32||0^32 (L0 is 32 bit 1, R0 is 32 bit 0)? 2) when input is input is ^064(L0 is 32 bit 0, R0 is 32 bit 0)? This is all I have...I ...
-4
votes
0answers
41 views

Why is plain ElGamal not secure?

Why is plain ElGamal not secure? What is the proof behind it?
-4
votes
0answers
37 views

What’s the output of two round Feistel network [on hold]

What’s the output of two round Feistel network, 1) when input is 132||032 (L0 is 32 bit 1, R0 is 32 bit 0)? 2) when input is input is 064(L0 is 32 bit 0, R0 is 32 bit 0)?
1
vote
1answer
55 views

(Simple) Tool for analysing performance (speed in particular) of cryptographic hash function?

I am doing some research for which I intend to insert some (external) function in different cryptographic hash functions and I would like to analyse how the insertion of this extra code in the hash ...
2
votes
0answers
54 views

Looking for C++/Python Open Source code library for cryptanalysis of classical ciphers

I've done a significant amount of coding over the years working on classical ciphers (e.g., Chaocipher, D'Agapeyeff). My main programming languages today are C++ and Python, although there was a time ...
0
votes
1answer
64 views

How much of Probability do I need to know to study Cryptography?

I have just started MSc in Computer Security. I didn't study probability before. Now, I have some short time to complete my MSc semester. What are the minimum topics from 'Probability' do I need to ...
2
votes
1answer
51 views

Algebraic cryptanalysis on public-key schemes

The book Algebraic Cryptanalysis (Bard, G.V.; Springer, 2009) speaks about transforming a symmetric scheme into a system of polynomial equations and solving these equations to break the scheme. But ...
2
votes
1answer
100 views

What use is the signature without the message under RSA?

Using RSA for signing & verification, is there a way to take a valid signature for an unknown message, and for someone else to generate a valid signature using a different key against the valid ...
1
vote
1answer
1k views

What is the probability of breaking the AES algorithm?

I am doing a project which requires the encryption to be done using AES. Is it really possible (technically) to crack AES? If yes, please tell me: What is the probability of breaking AES? How ...
5
votes
1answer
139 views

Crack linear congruential generator knowing every other word in sequence

I need to crack one of the example of linear congruential generator. I have $X_{n+1} = (a \cdot X_n + b) \bmod m$ and I know every other word in the output sequence: ..., 3158, ..., 1888, ..., ...
0
votes
1answer
78 views

What makes this mixer function resistant to differential cryptanalysis?

I recently learned how differential cryptanalysis works, and decided to have a play around with testing various designs for resistance against attack. My testing algorithm is essentially to loop ...
0
votes
0answers
27 views

Vigenère + columnar transposition

I'm trying to decode a text which is encoded by Vigenère followed by a columnar transposition. The method I want to use is trying random columnar transpositions and then rating how much the text that ...
0
votes
0answers
35 views

Recover keys using statistical saturation attack

I am having trouble here performing this attack on a block cipher. This is my block cipher, it is a toy with really bad diffusion just for the sake of performing a successful attack ...
-1
votes
0answers
63 views

How does this Cryptowall v3 working to encrypt the file?

In Wikipedia, I've found an explanation about this Cryptolocker, the predecessor of a new variant this Cryptowall v3. I think there's an interesting value to know more about this kind of Trojan. ...
2
votes
1answer
85 views

Stacked LFSR - why not used?

New to cryptographic, weak in math. I have designed a PRG which consist of 33 LFSR's, each 32 bits wide. I use one of the LFSR's as "selector", using the 5 LSB from this register to select one of ...
-1
votes
0answers
58 views

In modern definition, what is Enigma, and what caused its downfall?

This question is sparked from the movie The Imitation Game. This single question will have lots of subquestions. The Germans must put the Enigma at the same settings before encrypting and decrypting ...
4
votes
1answer
142 views

Can machine learning analyze random number generator?

I'm studying for random number generators(RNG) and I saw about machine learning a few days ago. So I searched analysis of RNG using machine learning. But I couldn't find such fields. Are there such ...
30
votes
11answers
6k views

Now that quantum computers have been out for a while, has RSA been cracked?

D-wave systems has released a commercially viable quantum computer. This means in theory, that all asymmetric encryption algorithms — such as RSA — are now useless due to the speed at which quantum ...
0
votes
1answer
81 views

How do you implement a cipher as one lookup table?

I am reading up on whitebox cryptography and have trouble understanding how are ciphers implemented as one lookup table? assuming my plaintext is just 4 bits so the size of my lookup table should be ...
5
votes
1answer
382 views

Purpose of expanding then shrinking in SHA-1

What is the purpose of expanding then shrinking in SHA-1? Does it serves any security purposes?
9
votes
1answer
631 views

How would one crack a weak but unknown encryption protocol?

I asked a question on security.stackexchange, but was told it would be a better fit here: http://security.stackexchange.com/questions/32779/how-would-one-crack-a-weak-but-unknown-encryption-protocol ...
0
votes
0answers
31 views

Practical strength of non-2^n RSA key lengths [duplicate]

It has for many years been popular to use RSA keys that have lengths that are powers of two. E.g. 1024-bit, 2048-bit and 4096-bit key lengths are all popular for use with OpenPGP implementations such ...
2
votes
0answers
51 views

Statistical saturation attack on block ciphers

I was wondering if anyone around here could give me some explanation on this type of attacks. Pretty much the only thing that I could find is this What I really need is basic explanation of the ...
0
votes
0answers
26 views

How to check if a sequence is generated by a linear congruential generator? [duplicate]

Assume a linear congruential generator is defined by $x_i=(x_{i-1}\cdot a+c)\bmod m$ and I am given the values $a$, $c$, $m$ and a sequence of numbers starting at the $n$th bit. Can I tell whether ...
1
vote
0answers
49 views

Statistical saturation attack on block ciphers

I was wondering if anyone around here could give me some explanation on this type of attacks. Pretty much the only thing that I could find is this What I really need is basic explanation of the ...
0
votes
3answers
186 views

When is a cipher considered broken?

We've all read how some people claim AES is broken because there was supposedly a way to get the plain text from a cipher text faster than brute-force. But is this the definition? Is a cipher broken ...
1
vote
1answer
53 views

Why are modes of operation used, what attacks do they prevent?

I know you always need to use a mode of operation when using a block cipher, AES for example, and Wikipedia has a good explanation for what modes of operation are Now I know if i do not use a mode of ...
-1
votes
1answer
85 views

Vigenere ciphers : Need help for math analysis

I've been learning about Vigenere ciphers and then thought of another method to Encrypt and decrypt that. This's my method to encrypt : ...
4
votes
2answers
283 views

Is Chaocipher a secure cipher under ciphertext-only attack?

Chaocipher was invented by John F. Byrne in 1919. The algorithm was recently revealed – see Moshe Rubin's Chaocipher Revealed, the Algorithm (PDF). While a known plaintext attack successfully finds ...
2
votes
1answer
43 views

Differences between Work Factor and Time Complexity

I am interested to know if work factor means the same thing as time complexity. Quoting Work Factor : Uncovering keys in cryptosystems The Work Factor of a cryptosystem is related to its ...
0
votes
3answers
146 views

Brute force against computational security

One-time pad is secure under brute force with respect to either of the definitions \begin{align} \Pr[M = m] &= \Pr[M = m | C = c]\\ \Pr[C = c | M = m_0] &= \Pr[C = c | M = m_1] \end{align} ...
1
vote
1answer
163 views

How to accurately calculate Unicity Distance for English?

The Unicity Distance for the DES cipher is around $8.6$ characters, and can be calculated using the $U=H(k)/D$ formula, where $D = R - r$, and where $R = 8$ is the number of bits in a byte (ASCII is 7 ...
-1
votes
1answer
63 views

Complexity of attacks on affine cipher

I am interested in the complexity of attacking affine ciphers under the following two scenarios during a Ciphertext only attack during a Chosen Plaintext attack For an alphabet of size $m$, how ...
0
votes
1answer
389 views

Is this encryption scheme perfectly secure?

Let $m = 6$, and let $\mathbb{Z}_m$ denote the set $\{0,…,m-1\}$. Let $X \mod m$ denote the remainder obtained when dividing $X$ by $m$. (a) Consider the symmetric encryption scheme in ...
1
vote
1answer
184 views

Is cryptanalysis of CTB-Locker really impossible?

It seems that CTB-Locker make a lot of victims nowadays, and yet, the full encryption scheme of it is now publicly known [1,2]. Would any of you could find a weakness to exploit in this encryption ...
4
votes
2answers
574 views

Is there a security analysis of CryptDB?

It's interesting to see critical thinking being applied to CryptDB in contrast to all the hoopla around it here. CryptDB is not a major theoretical breakthrough but potpourri of technologies to make ...
6
votes
2answers
7k views

How much computing resource is required to brute-force RSA?

It's been over 30 years since Rivest, Shamir and Adleman first publicly described their algorithm for public-key cryptography; and the intelligence community is thought to have known about it for ...
0
votes
1answer
54 views

Text in random image encoder: is it flawed?

I have created a small cryptographic programme: You input your text A random image is generated Random coordinate pairs in number equal to the chars of the message are generated. The red component ...
2
votes
1answer
63 views

How to construct the blind factors in practice?

I'm Implementing a protocol that uses masking techniques (or blinding factors), so we can mask a value $y_0$ as $m_0=y_0 \cdot r_0$ where $y_0 \in \mathbb{Z}_p$ and $r_0 \stackrel {R}\leftarrow ...
0
votes
1answer
301 views

Security of SecRandomCopyBytes on OSX and iOS

How secure is SecRandomCopyBytes() (Apple's RNG)? Has anyone ever reviewed it?
0
votes
1answer
62 views

Self changeable key [closed]

If key changes itself when it send/receive message what would be could breaking method? So: $E: m×k$ in which $k$ is last generated key $D: c×k$ in which $k$ is last generated key $k{_n} = ...
0
votes
2answers
82 views

Counter Mode with a sequence of zeros bits plaintext, is it secure?

I had a quiz last week in computer security course. There was a confusing question that I am still looking for a good and clear answer. First, I know that counter mode with a good block cipher is ...