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# Questions tagged [permutation]

A way, esp. one of several possible variations, in which a set or number of things can be ordered or arranged.

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### Total password count, given length and pool size

First, if my password is exactly 8 characters long, derived from a pool of 95 characters, then is the total amount of passwords I can create simply $95^8$ ...
635 views

### Pseudo-random permutation of a range

I have this set: {0,1,2,3,...,15}. I would like to create a pseudo-random permutation from elements of this set, for example ...
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### Can a random permutation be restored / decrypted?

Say you have a 1,000,000 random bytes file and you split it into 1000 x (1000 bytes) pieces. You then pick two random pieces and swap them writing down the position of the pieces (eg. swapped piece ...
153 views

### How to generate a permutation of n numbers using secret sharing scheme?

Consider $n$ parties having their private inputs $s_1,\cdots,s_n$. How can they compute a public function $f(s_1,\cdots,s_n)= \pi$, where $\pi$ is a permutation of numbers between $1,\cdots,n$, using ...
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### What is the importance of $f_k$ in a feistel network being a permutation

I was doing some cryptography exercises, one of which was an example of a feistel network. It said that the function $f_k$ was a permutation for all k but didn't explain why that makes a difference. ...
585 views

### substitution-permutation network construction

I want to understand more about substitution-permutation network, if we modify it instead of carrying out the key-mixing, substitution, and permutation steps in alternating order for r rounds, the ...
534 views

### Number of combinations required to brute force

I am trying to encrypt a password in a program. Here is the process: Let us assume that I have a string $p$ ($n$ characters long) which contains the password. Now the program reverse the string and ...
12k views

### How to solve Columnar Transposition Cipher without a key

I have been given a 77 character message for decryption, but no matter where I look all the Columnar Transposition scripts out there are all requiring of a key. I believe the number of columns to be 7,...
85 views

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### Block cipher and parity of permutation

Can anyone explain the following text passage to me? Most real-world block ciphers build even permutations, because it's hard to build odd ones using small operations (32 bit) on larger (128 ...
357 views

### derangements and permutations in cryptography

Given a partial key for a mono-alphabetic substitution cipher (missing 11 letters), calculate the number $N$ of possible keys, given that no plaintext letter can be mapped to itself. Ordinarily, ...
724 views

### No of keys used in Triple DES Algorithm

I am studying Triple DES. I have got two basic questions. One, why are we following a sequence like encrypt(decrypt(encrypt)); what is the problem using a sequence encrypt(encrypt(encrypt))? Second,...