If a person who debugs code is a debugger then the person who wrote the bugs must be a...
I gave a talk at the UKHAS 2013 Conference in September on debugging for high-altitude balloon enthusiasts. It applies more generally than that and may be interesting to others (especially if you are relatively inexperienced at programming and debugging).
The talk covers the basics of debugging without any specific programming language and is intended to be humorous but also useful. The folks at UKHAS were super organized and recorded the talks and synchronized the slides. You can listen to me give this talk by going to the BATC File Archive and then select HAB2013: my talk is HAB2013 03 Debugging.
If you've worked your way through the GCHQ Can you find it? recruitment challenge you'll have reached the last part and discovered that you have to do... nothing. The code word is accepted and you get to give your details for the competition. But you didn't do anything in part five.
That bothers me.
And there's another thing that bothers me. The second part includes a very obvious link to a web site (apparently correct) hidden inside an RSA private key, but the private key is messed up and messed up in a very specific manner.
So, another way of finding the answer to part two is to calculate (modulus-prime1)/2 to get the same printable ASCII containing a URL.
I wonder if GCHQ originally wanted to make part two harder and then changed their mind?
And then there's the relationship between exponent1 and exponent2. There are sections with repeating patterns (and oddly those sections seem to align with the 0x20 padding bytes in prime2 (see bolded sections above)). df:f6:88:71 repeats in exponent1 and e2:c2:a4:c4repeats in exponent2. Unfortunately, why those repeating patterns are present (indication of a simple XOR key used against repeating plaintext?) and how they are used to get further information elude me. Also, why are there some 'random' bytes after each repeating section? Last time GCHQ had a challenge I did find something interesting which was confirmed (with help from The Register) by GCHQ. I reached out to the same people via a dead letter box at the tomb of Thomas Bayes in Bunhill Fields cemetery and searched for a response via the personal ads in The London Review of Books but have heard nothing. So... has anyone else looked into this?