# 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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### Application of fixed point theory in cryptography

Does fixed point theory has an application in Cryptography? I really don't know about Cryptography. If you mention any books on this matter it really helpful
1answer
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### Proof that the group of non-generators in a multiplicative group with a prime order is a sub-group

I'm trying to solve the following problem - Let $\mathbb{Z}^{*}_p$ be a multiplicative group such that $p=2^k+1$ and is prime. I need to prove that the set of elements that are non-generators in ...
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### Different heuristics to solve the Caesar cipher

I know two heuristics that can be used to solve Caesar cipher, but I am asked a question in my artificial intelligence class to Give three heuristics that might be used for solving Caesar ...
1answer
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### Low public exponent attack in RSA

I am working in RSA. In one exercise I have to perform a low encryption attack for the given data: $e=5$ $n_1=18446744400127067027$ $n_2=18446744374357261961$ $c_1=7487701518489143755$ ...
1answer
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### Notation: Meaning of brackets with subscript?

I came across the following expression: $[m + 2r + 2\sum_{i \in S}{x_i}]_{x_0}$. What does the subscripted bracket notation mean? Context: Found in this paper https://eprint.iacr.org/2009/616.pdf. ...
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### Compute inverse polynomial over Finite ring

I want to know how to compute this, All this polynomials are over the finite field $\mathbb{F}_{2^8}$. I have that $$(x^6 + x^4 + x^3)^{-1} \equiv x^4 + x^3 \mod(x^8 + x^4 + x^3 + x + 1)$$ Where ...
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### Large sum of 1/GCD's

The problem is related to cryptography, it involves finding the sum of inverse of $GCD$... Say I have an integer $N \leq10^7$, Find sum of all $N/GCD(K,N)...$upto $N$ where $1\leq K\leq N$ Please ...
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### Encrypting plaintext with RSA encryption scheme

I have an RSA encryption scheme with parameters $p$ = 31 $q$ = 37 $e$ = 17 I've decrypted the ciphertext $y$ = 2, using CRT and got the following plaintext: $8440 = 721 \pmod{1147}$ Now I ...
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### RSA public encryption: Finding p and q given $\phi(pq)$

I have a quick question: My book asks me to show that if someone were to find that value of $\phi(pq)$ then they would be able to find out p and q. Is this possible? I've seen many examples of ...
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### Prove that $n$ is a pseudoprime to the base $b$ if and only if $b^d\equiv1 \pmod n$…

Question: Let $n = pq$ be a product of two distinct odd primes and put $d = \gcd(p − 1, q − 1)$. (a) Prove that $n$ is a pseudoprime to the base $b$ if and only if $b^d\equiv 1 \pmod n$. (b) ...
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### Let $m$ be a squarefree odd integer, and let $(a, m) = 1$. Show that $x^2 ≡ a \pmod m$ has a solution if and only if the Jacobian Symbol (a/p) = 1… [duplicate]

Something I have been struggling with! Let $m$ be a squarefree odd integer, and let $(a, m) = 1$. Show that $x^2 ≡ a \pmod m$ has a solution if and only if the Jacobian Symbol $(a/p) = 1$, for all ...
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### private key for a secret code“1983”?

Hi !! I tried to find information and examples to solve this RSA cryptography with public and private keys problem but couldn't find it.. This is my preparation questions for exam and not ...
1answer
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### Show that the number of bit operations necessary to compute f · g is O(n2 log2 p) (f,g ∈ Fp[x] of degree ≤ n).

Is anyone familiar with finding the time complexity on different computations? (Big-O-Notation) . My professor would always write down the bit operations for different computations, however, he would ...
2answers
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### Irreducibility of $x^3 − a$ over the field of $q$ elements

I have done much research on this specific question. I have come across many different theorems and definitions on this topic. However, I am having difficulties piecing them together to create a nice ...
1answer
22 views