# Tagged Questions

Questions on cryptography and cryptanalysis, encryption and decryption, and the making and breaking of codes and ciphers. Consider posting your question at Cryptography.SE.

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### Effect of seeds on the generation of keystream from a LFSR

I have a question regarding something I noticed about LFSR seeds. I tried different seeds in a simple LFSR with polynomial of “x4+x+1”, most cases I got equal amount of 1s and 0s in the keystream ...
10k views

### Calculator model with mod function?

I'm wondering does anyone know of a scientific calculator with a mod function? In C# this is shown as follows (just in case there are any other mods that a mathematical non-savant such as myself ...
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### dining metaphysicians

I thought I'd read about this problem years ago, but cannot find the answer online. There is a more well-known dining philosophers problem that is vaguely similar. https://en.wikipedia.org/wiki/...
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### Diffie Hellman Problem

I know that in Diffie Hellman, the final key (from Bob's point of view the final key is calculated as follows) KB = (gx mod n)y mod n, where x represents Alice's private no. y represents Bob's ...
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### Calculating Probabilities for Substitution Ciphers using Frequency Analysis

I have been trying to put together a tool that can take in cipher text encrypted via a simple substitution cipher and calculate the most likely "key" (that is, how the plain text letters were mapped ...
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### Suggest solutions book

Does somebody know solutions manual for book "An Introduction to Mathematical Cryptography" by Jeffrey Hoffstein, Jill Pipher, Joseph H. Silverman?
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### Is a possible use of a Mill's constant the encapsulation/encryption of messages?

I wonder if the way that Mill's constant is defined could provide a good data encapsulation and encryption method if instead of encapsulating primes, for instance a simple ASCII message is ...
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### Proof of an alternative form of Fermat-Euler's theorem.

I want to know a proof of an alternative form of Fermat-Euler's theorem $$a^{\phi (n) +1} \equiv a \pmod n$$ when $a$ and $n$ are not relatively prime. I searched some number theory books and a ...
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### How to provide Mathematical Proof for number theory scheme?

I have a set S={1,2,...,N-1}. N=pq (where p and q are RSA prime numbers). Scenario is that User need to retrieve the Database blocks without revealing his block index to the Server i.e, Private ...
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### How good is the pseudo-radom-sequence assuming the truth of RH?

The Riemann hypothesis is equivalent to the claim that the sequence of moebius-values (numbers not being squarefree are skipped) behave similar to a random walk. Let's assume that the Riemann ...
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### Discrete Logarithm vs Integer Factorization

Can anyone please tell me if finding discrete logarithm is considered more difficult than integer factorization? We have very advanced methods to find factors of large composite numbers like Number ...
1k views

### How to reverse this bitwise AND-XOR encoding algorithm?

I have been given an "encoding" algorithm that does bitwise XOR and bitwise AND. Originally it's a C code that operates on integers with bit-shifts, but I have translated it into a simpler pseudocode ...
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### RSA: Fast factorization of N if d and e are known

I stumbled across this paragraph in a paper: Hence, user b cannot decrypt C directly. But using e and d , user b can quickly factor N. How is it possible to speedup the prime factorization ...
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### How to solve a modular inequality with optimization?

I have this: $x\le y$ $y\lt m$ $x^2\mod m < y$ $y$ and $m$ are given. I am trying to maximize the value of $x$. Any advice on how to approach this?
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### On Pohlig-Hellman prime power discrete logarithm algorithm

If $p,q$ are odd primes and suppose we know $x\bmod 2^rp^tq^u$ in $g^x=h\bmod q$ where $2^{r+1}p^{t+1}q^{u+1}|\phi(q)$ and $g$ generates $\Bbb Z_{n}^\times$ then what is the procedure and complexity ...