Mathematics Stack Exchange
Mathematics Stack Exchange

Questions tagged [cryptography]

Questions on the mathematics behind cryptography, cryptanalysis, encryption and decryption, and the making and breaking of codes and ciphers.

Please only post questions about the mathematics of cryptography here.

  • Coding and implementation specific questions should go to Stackoverflow with encryption or cryptography tags.
  • You may also consider asking at Cryptography Stack Exchange which is for asking questions about the mathematics and properties of cryptographic systems, their analysis ("cryptanalysis") and subsidiary topics that generally make up cryptology.
1915 questions
0
votes
0 answers

How to figure out one of the keys in an affine cipher?

I have been told that one of the keys in an affine cipher is 33. The Mod is 37 - the set being the alphabet + numbers + space. So the affine function is $ax + b$ $(mod$ $37)$ with $a$ and $b$ being the keys. I cannot figure out if $33$ is $a$ or…
Rob Bor
  • 147
  • 1
  • 6
0
votes
1 answer

Understanding an excerpt of notes on RSA using the Chinese Remainder theorem

I have a description in my cryptography notes of a way to make RSA more efficient using the Chinese Remainder Theorem. Let $p,q$ be large primes, $N=pq$ , $e$ be the public encryption exponent, $d$ the private encryption exponent. I will only ask…
IntegrateThis
  • 3,778
0
votes
1 answer

Impossible ElGamal signatures

From the following problem, I think it is not possible: " You find two signatures made by Alice. You know that she is using the ElGamal signature scheme over $\mathbb{F}_{2027}$. The cyclic group $\mathbb{G}$ she is using is a (multiplicative)…
Rocco van Vreumingen
  • 321
0
votes
2 answers

What do some cryptographic terminology mean?(e.g. public params, security params)

Setup($1^\lambda$) $\to \mathcal params$. On input security paramater,output a set of global public parameters $\mathcal params$ Can you give some examples to explain the cryptographic terminology? Mint($\mathcal params$) $\to (\mathcal c…
Deleted
  • 11
  • 2
0
votes
1 answer

How to find n elements of order o in U(m)

For example, to find 4 elements of order 47 in U(187), is there a simpler way to do it instead of finding 2 more numbers except 1 and 186 by going through all possibilities from 2 to 185?
user9826208
  • 1
0
votes
2 answers

Vigenere Cipher

I have converted a piece of plaintext to cipher text using an 8 letter keyword. After attempting to solve my vigenere cipher, I realise it is very easily solveable. So my question is, how can I create a more difficult encryption using the vigenere…
Crypto
  • 1
  • 1
0
votes
1 answer

How to pick a random polynomial such that $f(-1) = a$, $f(-2) = b$, $f(-3) = c$ ... given $a$, $b$, $c$ ...?

I'm learning (well, reading about and struggling to comprehend) a variant of Shamir Secret Sharing that goes like this: Luckily, Shamir’s scheme can be generalised to what we’ll called the packed scheme, which removes this last constraint. Now,…
Meler Lawler
  • 103
0
votes
0 answers

Hill cipher , known plaintext attack.

I know the plaintext and ciphertext. I want to find the vector key which is used to encrypt the text. here is the step I want to do. The convert the ciphertext and plaintext into matrix of n x n. Find the inverse of the matrix which is equal to…
Da Born
  • 13
0
votes
1 answer

Get the average score without showing anyone's

$n$ guys each have a score in $[0,100]$, and they want to know their average. However they don't want their score to be known by others, even if the other $(n-1)$ ones are all dishonest. They can accept a not-that-accurate result for safety. If…
l4m2
  • 211
0
votes
1 answer

Calculate inverse square root modulo (Feige-Fiat-Shamir Algo)

I would like to calculate a secret key, $s$: $$ s = \sqrt{\frac{1}{v}} \mod n $$ where v is the public key, n is a product of two primes p and q. (maybe we can use something simple like 7 in this example?) Can someone please provide a step by step…
hairybear
  • 15
0
votes
1 answer

Find the message on Hill Cipher

We assume that the message $$!IWGVIEX!ZRADRYD$$ has been encrypted using Hill Cipher and with the correspondence $A=0,...,Z=25,\ \_=26, ? =27,!=28$. We know that the last five letters of plaintext are sender's signature $MARIA$. We want to find…
Chris
  • 2,763
0
votes
1 answer

RSA: Factorising $n$ using square difference

I am working on the following exercise: I have to show that if for the two primes $p$ and $q$ used in RSA to compute $n$ holds: $$p < q \le (1+\epsilon)*\sqrt{n}$$ one has to test at most $\frac{\epsilon^2\sqrt{n}}{2}$ values to find integers $s$…
3nondatur
  • 4,178
0
votes
0 answers

Solving a (short) famous cryptogram

I have been trying to decipher the cryptogram below for quite some time now, but I'm not getting a solution. The text should be in English and it should be a world famous cryptogram. It is possibly polyalphabeticallly ciphered. 53 ‡ ‡ † 305))6∗;…
3nondatur
  • 4,178
0
votes
2 answers

Decrypting RSA cipher text when given N e and d

The cipher text is wqlizYbFyjOp95Bt.ViLWHhEBx2 N=7231645985673347207280720222548553948759779729581 e=3 d=4821097323782215625692549251331855329314609896043 where d is the private key How do i solve this?
Pkr96
  • 87
0
votes
1 answer

Need help finding a blog post

Here are what I remember: It is either a post on a rather famous blog or maybe an arxiv paper. Pretty sure it was a post. Regarding the contents (I don't quite remember that well so there might be inconsistencies), it had a fictional story about two…
jonathanasdf
  • 103
  • 3
1 2 3
…
18 19