Silly Science Electronics, Programming and Hacking About


Can you crack it? Stage 3 solution

Once getting through stage 2 you will have an EXE file. It requires windows (I ran it in a VirtualBox VM seeing as I had no idea what it would do - can't be too careful!), cygwin and the crypt library when installing cygwin.

Running the EXE you will see that you require some kind of license.txt - if you create an empty one then you get an error about it being invalid. The next stage is working out what is required to make the license.txt file valid. Being new to this realm of reverse engineering, but being comfortable with work with ASM I tried a number of tools - strace, objdump and strings. Each yielded useful bits of information - especially strings.

However the real breakthrough came when I ran the exe file through a tool called IDA Pro - the freeware version is sufficient for this exercise.

Running the binary through IDA Pro produces a very comprehensive flow of the program. If you navigate this flow you will being to see calls to printf which relate to the message we get on the screen.


Can you crack it? Stage 2 Solution

There has been a lot of news about the "Can you crack it?" challenge that is currently to publicise GCHQ recruiting. Here is my solution for stage 2 - the implementation of the Virtual Machine, or emulator. It's actually pretty straight forward when you get a hold of a few of the nuances. I'll put a list of hints here, and then present the full solution after the fold.

  1. As of stage 1 - everything is centred around the x86 architecture, this means that your instructions need to mirror the behaviour of their x86 equivalents
  2. Firmware seems to be irrelevant - don't worry about it.
  3. There is no real trickery here - it's just a straight forward instruction set simulator implementation
  4. The programme will finish on a HALT instruction

This is actually quite a neat little program that works by decrypting itself further programme code which it then runs and decrypts the message to get to the next stage... enjoy...


Humorous Scam E-Mails

I usually totally ignore these 419 emails, they drop right into my Spam box - but this one was really quite funny, and oddly came from HK/China (they usually appear from Africa!).

Anyway, I was massively excited by a whole $17.3 - wow! And he has done the underground works - totally legal - awesome!




I am contacting you as the senior manager in a bank in China and financial advisor and account officer to a private investor about fund deposit totaling $17.3. I assure that the transaction is 100% risk free and legal having done all the underground works.


As soon as I receive a response for your interest, I will send you the complete details of the successful completion of this transaction. Please contact on my private email below for further clarification.

Best regards,


Jan Yiun


Create a PDF of images (PNG, JPG, GIF etc) on Mac OS X with Preview

PDF document icon

I recently wanted to compile several images into a single PDF document - after searching for a relevant tool and discounting Word or iWork as too time consuming I hit upon the following very simple solution...

  1. Open one of the images you want to put into your document in Preview
  2. Now open the 'Sidebar' (if it isn't already open)
  3. Drag the rest of the images into sidebar in the order you wish them to appear in your PDF document
  4. Select all the images in the sidebar (Cmd+A)
  5. Do 'File -> Print' and click the 'Save as PDF'
  6. Follow the prompts to save the file and you should now have a PDF containing all your images!

Installing gitorious on Ubuntu 10.04 HOWTO

I like using Git for my projects and I tend to host them outside of the computer I work on. I was finding the current way I was managing projects a bit cubersome so I decided to install Gitorious which gives you a nice web interface to manage it all!

Here are some instructions on installing Gitorious on your own Ubuntu 10.04 LTS server. The instructions from gitorious were a little out of date/confusing so I thought I would show you what I did to get it working successfully. It is based upon instructions from both gitorious' own instructions and some others they link to, plus some other digging/googling around [1][2] and [3].

Updated: Added some fixes/clarifications from the comments below! (If you spot any errors do please tell me!)

A few notes on this tutorial: Firstly - This tutorial is approaching it's first birthday which means (as with all things like this) it is getting somewhat outdated. With that in mind - approach with trepidation. I would read up on the relevant documentation from the developers yourself and make up your mind how helpful / relevant to you this whole process is.

Secondly - I have now moved to indefero (see this is a lot easier to install and manage - offers all of the functionality that I have needed - which more than makes up for the lack of prettiness that gitorious had...


rsync Backup / Dropbox style setup

This tutoral/HOWTO is designed to help you setup an rsync back/dropbox style synced folder on the Netgear stora. The aim of this is to have a synced folder that will automatically back up to a remote location. The main reason that I wanted to do this was so that I could have a folder of documents backed up to my VPS and synced to my work machine and laptops.

It is similar in style to the 'dropbox' service. It is largely based on this HOWTO. It just covers a number of points for installing on the Stora!
This guide assumes you have a fully working package management system as described here - Installing a package manager and also assumes that you have SSH fully working.


Useful Server Setup Tutorials

So I decided to take a leap and move VPS providers. Moving servers turns out to be hard work. Here is a list of useful stuff that I had to dig out again when setting up the new one -

As I find more of these I will update them as and when...


Netgear Stora and Time Machine Setup

Netgear Stora NAS boxHaving just got a Netgear Stora I wanted to use it as my time machine backup (I have an old ibook G4 and 10.5 so some of this may or may not work for 10.6 - i haven't tried it!). It turns out this isn't a simple operation (despite ease of use supposedly being a big selling feature of the Stora...). Here are the steps I eventually worked my way through to get this working:


Open Workbench Logic Sniffer First Impressions

Open Workbench Logic Sniffer Board Photo A while ago I spotted the Open Workbench Logic Sniffer on Hackaday. A logic sniffer . analyser is a useful tool have around the place and at ~$50 with some flying leads to make it up to the free shipping threshold. Seeing as it arrived the other day I thought I would share my first impressions of it...


Microchip Development Kit & Programmer for Sale! (SOLD)

As I no longer have any need for them I dug out my EasydsPIC4 and Microchip ICD2 (In Circuit Debugger) the other day and they have made their way to ebay. You can get the EasydsPIC4 development board/kit here SOLD and the Microchip In Circuit Debugger (ICD) 2 here SOLD. More info after the break...