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
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Determine if an algorithm has solutions or not

I m actually studying Turing works concerning Enigma's machine. Actually, I am wondering if it does exist anything, an algorithm or something that allows people to tlel if an algorithm can be break or not. For example, admitting that we're working…
mfrachet
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How to expand Diffie-Hellman key exchange for multiple users?

To provide OTR (off the record) security for XMPP group chats we've discussed an idea for a Diffie-Hellman key exchange algorithm for multiple users. It should work as follows: Choose a cyclic group $G$ with the order $p$ prime and a generator $g$…
Heywood Floyd
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Does RSA use two one-way functions?

I'm trying to understand the concepts behind RSA right now. From what I've learned so far, it's pretty much all about a one-way function with a trapdoor: Raising the message to the e'th power modulo N, where the factorization of N is kind of the…
Reignbeaux
  • 101
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Why wasn't the length of key mentioned in this algebraic notation of Vigenere Cipher?

Let, $M=m_ 1 m_ 2 m_ 3 ... m_ n$ and, $K=k_ 1 k_ 2 k_ 3 ... k_ m$ Then how algebraic notations of Vigenere Cipher should be? In the following pages key-length and message-length are shown same. This page. This page. This page.
user6704
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Solving ANF equations

Can anyone suggest a method of solving a system of boolean equations in ANF form? Boolean equations in ANF form (Algebraic Normal Form ) are equations of the form of xor of products of boolean variables. For example (($x_1$ and $x_2$) xor ($x_2$ and…
The Doctor
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Breaking RSA code

I will be grateful for some tips on how to bite a task like so: I need to break a RSA code. I know that public key is $n=462257, e=13$. I also have cryptogram $c=139552$. The goal is to find a number that is encrypted here. I have written some…
Cris
  • 131
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Affine cipher does not satisfy the diffusion property.

Generally, we know that substitution ciphers do not have the property of diffusion. And affine ciphers is the special case of substitution ciphers. But how can we prove that affine cipher does not satisfy the diffusion property?
express78
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Stream ciphers - Block ciphers

What is the difference between the stream ciphers and the block ciphers?? Is the difference the time complexity?? At the block ciphers the message is cut into parts of $n$ characters. If we have for example the word "anna" in two parts, then the…
Mary Star
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Superencrypting an affine cipher

I am curious - If I had a text that I encrpyted with an affine cipher, would superencrypting with another affine cipher (after the first) increase the mathematical security in the final answer? What if we encrpyted with affine first, then shift? I…
Jackson Hart
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Given an encryption key in a transposition cipher, find the decryption key

I am continuing my practice on problems for my cryptography class. I'm starting to get the hang of basic ideas of ciphers. At least i thought this until I attempted to do the follwng problem: The encryption key in a transposition cipher is $(5, 12,…
user655321
  • 133
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Reversible modular exponent in cryptography

I know this is possible from working code, but I can't wrap my head around how. For the given equation: $b = x^p\bmod\text{public_key}$ Where $p$ is prime ($131$ in my case). How to compute a public_key such that $x$ can be solved?
patrick
  • 101
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Identify encryption scheme - possibly DSA or Diffie Hellman - only client shares key

I could use a hand in identifying the encryption scheme used in this scenario. (Its from source code known to work) There is a client connecting to a server such that: client_private_key = rand p = 131 # known prime client_public_key =…
patrick
  • 101
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Why in cryptography it is common to use the SAME key for all the group?

I believe that it is safer that each member should have his or her encryption and decryption keys that no one else knows. IN this case a message $m$ is sent as $m^{e_1}$ the receiver sends $t$ back as $m^{e_1e_2}$ the sender decrypts his/her by…
e.ahmed
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Generating a quadratic polynomial in RSA (cryptosystem)

Question: Suppose that n is the product of distinct primes p and q, so n=pq Show that p and q are the roots of the quadratic equation x^2 -(n+1 -φ(n))x + n Hence if n and φ(n) are known then n can be easily factored. So far I know that…
AnalysisisKey
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Replacement Cipher

Replacement cipher: Let τ be a permutation of the alphabet, and apply τ to each letter of the message. Frequency analysis is useful for breaking this type of code. Decode the following, which was encoded using a replacement cipher. MIZVN KXXHA XRRTK…
UserX
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