# Code Blue CTF 2018 - Lagalem Writeup

We’re given a piece of Python code and the result of the encryption of the flag:

1 | from Crypto.Util.number import * |

## Code Analysis

Analyzing the code we have:

, random primes such that random values random that is the flag , , , that are the encryption results

## Attack

We’re given

Now recalling Fermat’s little theorem: if

Noticing that

The Python code to perform this attack is the following:

1 | def tobytes(n): #long to bytes |

that prints out the flag: `CBCTF{183a3ce8ed93df613b002252dfc741b2}`