1
vote
1answer
22 views

Relation of encryption to P, NP, and NP-Complete

After watching a Harvard Lecture regarding the understanding of P, NP, and NP-Complete,they also talk about our encryption algorithms being cracked or useless once we solve the mathematics side of it? ...
5
votes
2answers
145 views

Understanding Intel's white paper algorithm for multiplication in $\text{GF}(2^n)$?

I'm reading this Intel white paper on carry-less multiplication. For now, suppose I want to do multiplication in $\text{GF}(2^4)$. We are using the "usual" bitstring representation of polynomials ...
0
votes
1answer
62 views

ElGamal Public Key Cryptosystem and Digital Signature Scheme

I'm tryting to understand how ElGamal algorithm works, and I got the following example, and I couldn't understand one part of this: A) P=23, g=5. B) x=3, then y=10 (for 53 mod 23=10 ). C) Sign for ...
2
votes
0answers
177 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 ...
0
votes
1answer
78 views

Help me this proof! Related to RSA public key cryptosystem

Basically it is similar to the RSA algorithm. Let p and q be distince primes and let e and d be the integers satisfying $de≡1$ (mod (p-1)(q-1)). Suppose further that c is an integer with ...
1
vote
1answer
67 views

How to determine which encryption system is being used?

I came across this question in a local contest. I was not able to solve it at that time. Also, no solution was provided. I was wondering if someone can help me to understand how to tackle this kind ...
2
votes
1answer
54 views

How to compute $x$ and $y$

How can one find in an efficient way $x,y \in \mathbb{Z}$ with max$\{|x|,|y|\} > 0$ as small as possible such that $\mid \pi x + e y \mid < 10^{-4}$ ? I have reduced the following lattice ...
2
votes
1answer
406 views

How to compute the modular multiplicative inverse on WolframAlpha?

$e = 17$ $\varphi(3233) = (61 - 1)(53 - 1) = 3120$ Compute d, the modular multiplicative inverse of e (mod φ(n)) yielding d = 2753. ...
2
votes
1answer
168 views

Computing RSA Algorithm

Modulus $N=247$; encryption exponent $r=7$ Encrypt $100$; Decrypt $120$. $Solution:$ Encryption of $100$ is $35$. Decryption exponent of is $31$. Decryption of $120$ is $42$. For a discrete math ...
0
votes
1answer
75 views

Explanation on step $\rho$ of the SHA-3 algorithm

I'm working on implementing SHA-3 in a PIC microcontroller. In the block permutation, I don't quite understand step $\rho$: Bitwise rotate each of the 25 words by a different triangular number 0, ...
0
votes
0answers
71 views

How would I create a birthday attack? (Hash Functions)

I'm trying to create an birthday attack, but I can't seem to get through it as I've never done it before. The basis: We have $E_K$, an encryption function, which has $N$ possible keys $K$, $N$ ...
7
votes
2answers
190 views

Who is the oldest? (in a non-revealing way)

How can a group of people figure out who is the oldest, without revealing any other information? Revealing all the ages to a trusted third party is not allowed. Preferably I'm looking for solutions ...
4
votes
1answer
146 views

Does the difficulty of discrete logarithm depend on the difficulty of integer factorization?

The security of many (most? all?) public-key cryptography systems are based on the difficulty of the discrete logarithm or integer factorization. Are these two problems related at all? With the ...
1
vote
0answers
46 views

Algorithms for Performing Large Integer Matrix Operations w/ Numerical Stability

I'm looking for a library that performs matrix operations on large sparse matrices w/o sacrificing numerical stability. Matrices will be 1000+ by 1000+ and values of the matrix will be between 0 and ...
4
votes
1answer
102 views

Are there any secure ciphers you can use without a computer?

I have some kids that like encryption schemes such as the Caesar cipher and the Vigenère cipher. I would like to teach them something that's not easily breakable by todays maths and computers, but I ...
12
votes
3answers
310 views

Can we compare two secret numbers?

If you and I each have a secret number, is there a way we can find out whose is larger without either of us revealing our secret number? Clearly a trusted third party could do the job, but I was ...
1
vote
1answer
107 views

How to randomly sort a sequence efficiently and simply?

Let me ask whether my instant simple algorithm has serious flaws ,for cryptography use, or not. Which is supposed to randomly change the order on a given sequence S[1..n] of the length n. Assume I ...
1
vote
1answer
97 views

RSA calculations

I can not find a solution to the following problem. The problem is: We have an algorithm A for a decision problem that answers yes or no and for every input it gives the right answer with ...
0
votes
3answers
173 views

confusing in SEAL (Software-Optimized Encryption Algorithm) mathematic notation

I'm developing an encryption software based on SEAL algorihm for my research. I found the paper in here My Question is what is the meaning of $$ H_{i \operatorname{mod} 5}^i $$ in page 5? ...
0
votes
1answer
485 views

Questions about cracking playfair using a 'shotgun climbing hill' method

I see this page before. Cracking Playfair code And I download the C file in it.However,I am still confused about the code. How to evaluate a solution? What does this mean? ...
1
vote
2answers
352 views

Running 'Encrypted Code' on a Computer

Alice released a new version of her software for removing red-eye from pictures. However, she wants to protect her secret algorithm from disassemblers and such while still letting her customers remove ...
3
votes
3answers
458 views

Encrypting algorithm

I know there are some encrypting algorithm that once the text (the message) is encrypted there is no way to decrypt it. I can think one way of doing this: using as encryption key the current date at ...