https://academy.hacking-lab.com/events/6/challenges/56
The dump.sql contains a table with encoded credit card numbers.
From the hints it's clear that no encryption was used, but a strange mapping.
The smile :) can probably be ignored. We do know that any character has to map to the range of 0-9.
For example QVXSZUVY\ZYYZ[a has ACII codes in the range of 81-97 (which is more than 10).
It's easily visible that the ASCII codes are increasing from left to right. So we suppose that the characters position is influencing the mapping.
We have to find a simple mapping going from 81 (at position 0) to 97 (at position 14) to the new range 48-57 (='0' to '9').
0 'Q' 81 51
1 'V' 86 55
2 'X' 88 56
3 'S' 83 50
4 'Z' 90 56
5 'U' 85 50
6 'V' 86 50
7 'Y' 89 52
8 '\' 92 54
9 'Z' 90 51
10 'Y' 89 49
11 'Y' 89 48
12 'Z' 90 48
13 '[' 91 48
14 'a' 97 53
After playing around with the provided CC numbers (in decode.js) we find a constant offset of 30 and a position related offset.
With following JS script I can translate the flag:
var cc = 'SlQRUPXWVo\\Vuv_n_\\ajjce'
var str = ""
let offset = 30
for(i=0; i<cc.length;i++) {
let char_code = cc.charCodeAt(i)
str += String.fromCharCode(char_code-offset-i)
}
console.log(cc,str)The logged solution is
HV19{5M113-420H4-KK3A1-19801}