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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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How to generate a simple RSA key to encrypt a very short message?

I'm trying to encrypt a message with RSA. I'd like to do this as part of a game/scavenger hunt I'm organizing for the holidays. I understand how RSA encryption works but I'm having trouble finding a way to encrypt and decrypt the message. I found…
USB_Connector
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Validity of ElGamal signature variation

I'm trying to solve excersise 7.6 from Hoffstein - Introduction to Mathematical Cryptography page 459 (hhttp://goo.gl/oRyInT) Let $p$ be a prime and let $i$ and $j$ be integers with $gcd(j, p − 1) = 1$. Set $S_1 \equiv g^i v^j \mod p$, $S_2 \equiv…
Levitan
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How to decode the message?

This message has been encoded by a monoalphabetic function $f(p)=p+b~ \pmod{26}: APHUO~ EGEHP~ PEXOV~ FKEUH~ CKVUE~ CHKVE~ APHUO,$ where we digitize the alphabet by letting $A = 00, B = 01, . . . , Z = 25.$ I want to find the original message. For…
Nil
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How to find the phi function of very large numbers

I'm trying to decrypt an RSA encryption given that c: 8533139361076999596208540806559574687666062896040360148742851107661304651861689 n: 769457290801263793712740792519696786147248001937382943813345728685422050738403253 e: 65537 I plan on…
martin_thuriaux
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Zero knowledge protocol - Information exchange

I have a past exam paper question on zero-knowledge and I'm trying to figure out to understand properly. My lecturer said if Bob says to Alice "you might know" it is a non-duplicate if it is a duplicate then Bob is "sure Alice doesn't know",…
Kristof S.
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Vigenere Cipher Key Security

Example Key 1: EEEE Key 2: ERTY What are the advantages of using key 2 over key 1 and why?
Ewen Seck
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RSA cryptosystem - discrete secret primes

Why do we bother to take $n$ as a product of two secret primes in RSA cryptosystem? If $e$ is public, $d$ is private and prime factorization of $n$ is not secret, what would happen?
ChakSayantan
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decrypt elgamal encrypted message

I have this exercise and I'm stuck on the last question (I'm translating it from French so excuse me if I use incorrect terms) : Lets assume an El Gamal cryptosystem. Alice choose $p = 11$ and $g = 3$. She also choose $ a = 4 \\$ What is Alice…
Slite
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The oringinal massage in the RSA cryptosytem and coded massage both are the number in [0, n-1]

The actuall message M in the RSA system can be any number between 0 and n-1. The coded message R is also a number between 0 and n-1, but can it be any such number? I am litlle confuse about the question it asks, "can it be any such number?" so what…
ssyylar
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Why do we use prime numbers with RSA?

I coded a small example of RSA in Python. When filling p and q, I mistakenly put in two numbers that were not prime numbers. And it worked fine anyway. My question is, why is it so important for RSA to take prime number as inputs?
Milodupipo
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Decipher the message $2081\ 2182$ knowing that it was encrypted using the RSA system with the key $(2537, 13)$

Decipher the message $2081 \ 2182$ knowing that it was encrypted using the RSA system with the key $(2537, 13).$ $(2537, 13)$ is a public key $(n, e)$. To decipher the message I need to find the inverse modulo of e which is d: $$d= e^{-1} \mod…
user9132502
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cryptography , please help

I have a cipher system with $n=p_1\cdot p_2\cdot p_3$ , where every $p_i$ is prime , and a message $M$ ciphered in the following way $$E(M)=(M^{K_1})\mod n$$ I need to find the minimal number of unhidden messages in this system , and I have no…
Tomer Avira
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