All posts tagged WeChall

Stegano I problem statement is as follows

This is the most basic image stegano I can think of.





Nothing much is there in this challenge. Open the BMP file either in a text editor, e.g. Notepad or in any standard hex editor. After the binary data ends, the following appears

Look what the hex-edit revealed: passwd:steganoI

The solution is

Get Sourced problem statement is as follows

The solution is hidden in this page

It clearly instructs to have a look into the source HTML of the challenge page itself. Right click on the page and select “View HTML source” or something similar depending on your browser. Find for the obvious keyword “password”. At the bottom of the page, you’ll find

So, the solution comes out to be


Prime Factory problem statement is as follows

Your task is simple:
Find the first two primes above 1 million, whose separate digit sums are also prime.
As example take 23, which is a prime whose digit sum, 5, is also prime.
The solution is the concatenation of the two numbers,
Example: If the first number is 1,234,567
and the second is 8,765,432,
your solution is 12345678765432

Instead of readily jumping into writing into a program to crunch digits, I used WolframAlpha to solve this challenge. Even for free subscribers, WolframAlpha allots a computation time, which, in most of the cases, enough to solve challenges that appear in such websites and other CTF competitions. Apart from mathematical notations, WolframAlpha can understand natural languages to a large extent. Something like “primes > 1 million” in the WolframAlpha expression box or alternatively pasting this query in browser’s address bar, either will do.  Quick mental calculations shows that 1,000,033 and 1,000,037 are the first two numbers having a prime sum of digits. Hence, the solution is