Ok, now these kinds of challenges are not really good. The reason is that without any extra property, they are trivial. Here is why:<p>Let's assume you have a cyphertext c, of length l (ie |c| = l). Now I take a plaintext p of length also l (|p| = l). Let the key k be c xor p. Now<p><pre><code> c xor k = c xor (c xor p) = (c xor c) xor p = 0^l xor p = p
</code></pre>
Where 0^l is a string of l zeros. So yeah, given one cyphertext, I can craft a pair of key and plaintext such that there is a cypher (simple xor) that, given the cyphertext and the key, outputs the plaintext.<p>What is worse? I can craft |E|^l of such plaintexts (where |E| is the size of the alphabet).<p>So yeah: this test only checks if people know basic cryptography and boolean algebra. Which tends not to be a very good test[1,2]<p>[1] <a href="http://techcrunch.com/2011/05/07/why-the-new-guy-cant-code/" rel="nofollow">http://techcrunch.com/2011/05/07/why-the-new-guy-cant-code/</a><p>[2] <a href="http://devinterviews.pen.io/" rel="nofollow">http://devinterviews.pen.io/</a>
Can anyone here point me in the direction of what I should be reading in order to attack a problem like this.<p>I literally have little to no idea how to start.<p>Give me a reading list, or outline the first few steps!
According to <a href="http://www.bbc.co.uk/news/technology-15968878" rel="nofollow">http://www.bbc.co.uk/news/technology-15968878</a> it's for GCHQ rather than MI5.
Working on it here: <a href="http://forum.xda-developers.com/showthread.php?p=19888836" rel="nofollow">http://forum.xda-developers.com/showthread.php?p=19888836</a>
don't know if this means anything at all but exif info on the photo has a comment: QkJCQjIAAACR2PFtcCA6q2eaC8SR+8dmD/zNzLQC+td3tFQ4qx8O447TDeuZw5P+0SsbEcYR78jKLw==
/index.asp oh please, what's a challenge worth when I can find out the solution without solving it, by going to the application url. My naive proxy thought it's advertisment and didn't allow me apply hehe.<p>also we're lucky they exclude non-british folks, that way they interchange doubtable trust measures with infosec beginners.