# All Questions

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### Convolution and catastrophic codes

i'm reading the article of Massey and Sain (here) and i cannot unserstand - what is "foreforward inversion"? I mean There is a description of circles in convolutional codes and a little bit ...
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### Cryptanalysis and Copying encrypted volumes

I just recently concerned myself with cryptography due to Snowden's revelations and there are a few things I cannot really wrap my head around but maybe you can help me with that. I am not a ...
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### Join Datasets While Protecting Anonymity

I've run into this issue a couple of times in my career. I'll see if I can explain with an example (please ignore the fact that this is implausible in the real-world). Suppose I sell computers, and I ...
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### Can a combination of encryption algorithms weaken the overall encryption?

Are there any instances where a combination of industry standard encryption algorithms can weaken the overall encryption of the data? As a Naive example using non-standard encryption algorithms, ...
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### Understanding the PRINCE cipher linear layer

I am struggling to understand how to implement the PRINCE cipher linear layer. (https://eprint.iacr.org/2012/529.pdf) From my understanding I need to multiply the state with M, and with M' in between ...
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### How to find an impossible differential?

Given an arbitrary SPN-based cipher with X rounds. How to find an impossible differential for this cipher? What are strategies to find one?
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### zero knowledge framework for c programs - how to prove correct C program execution with private inputs

I am looking for a zk framework that could be used for proving correct execution of programs written in C (or any other high level language) such as: I know x s.t. SHA-256(x) = y (y is public, x is ...
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### Vigenère cipher frequency analysis not working

I'm writing a C++ program to use the Kasiski method to crack the Vigenère cipher. I'm testing it with a bit of Shakespeare encrypted with the key ABCDEFGHIJKL. It ...
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### Unicity Distance - AES

I am quite confused calculating the unicity distance and I was hoping that someone can clarify some things for me. My main issue comes from somewhat a difference of the calculation given by our ...
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### AM protocol for 2 distinct objects

Prover is going to convince verifier that 2 objects are distinct, do you know any Arthur-Merlin protocol for this problem?
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### Solving discrete logarithm when p is not a safe prime

If you have the cyclic group of integers modulo $p$, where $p$ is not a safe prime, as well as a generator $g$ with which for all factors $q$ of $(p-1)$, $g^{(p-1)/q} \ne 1$, This answer says that ...
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### Generating whitening keys through encryption

Question, if I generated whitening keys by encrypting the plaintexts of 0000... and 0A0A... would this reduce vulnerability to meet in the middle and related key attacks? If so, any rough idea of how ...
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### Anyone familiar with domain of hash functions in bilinear pairing based system?

I need a clarification regarding domain of hash functions. I have defined a bilinear pairing based system as follows: Let G1 and G2 be cyclic multiplicative groups of prime order p generated by g1 ...
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### Property of Multiplicative group of integers mod n

While practising on paper I've realized of a property of multiplicative group of integers mod $n$. First, let's define $G$ being $p$ a prime and $g$ a primitive root mod n or a generator of a ...
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### Is it possible to make an encrypted text look like a sentence consists of random words?

Without having any knowledge of common encryption methods, I wonder if an encrypted text can look like random valid words as if it is a sentence. Is it possible? If so, what methods should I use?
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### verify fails on 3rd party after signing with BouncyCastle

I am using BouncyCastle to perform ECDH and then encrypt the data between the mobile (Android) and my hardware with ECIES. It all works fine. When I try to sign a byte array and send it to the ...
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### ElGamal Generator g problem

Having an ElGamal encryption scheme with p=19 which value can not be assigned to g? The answers were : 1,7,11,2 I think you can't assign value 1 to g.
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### Determine encryption method with input and output

A website stores username and password in a session cookie. In the cookie the password is "encrypted" or modified in some way. Given that the "encrypted" version is always the same, I do not believe ...
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### side channel attacks against TDES (compared to AES)

We all know AES has some pretty strong side channel attacks, some where (with a couple of hundred know plain- and ciphertext combinations) a key can be derived in a matter of minutes. Others may take ...
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### Protocols with deliberate errors

This question is motivated by discussion cocerning “The Two Sheriffs” puzzle, see (1) and (2). Are there any public key protocols where Alice and Bob intentionally insert errors in their messages? ...
I know the following construct is insecure if the MAC as defined below is appended to the encrypted message in an Encrypt then Authenticate (EtA) scheme. $k_1$: encryption key $k_2$: authentication ...