Proving bit flipping attack on RC4 stream cipher (if weakly implemented)

Hi Guys! in this article we will somehow go to the world of cryptography wherein the hackers play a hide and seek or cat and mouse with the cryptographers. The cryptographers develop encryption to secure information...now hackers break it.....steal something. The technology users caught in between believing that their private files is secure.....only to realize that hackers has stolen their private digital belongings ranging from as simple as picture of the lady you fantasize..... to as serious as bank account......etc. Anyway, in here I just show you a simple way to demonstrate bit flipping on stream cipher. This is changing part of an stream cipher encrypted message without knowing the key. I will be using RC4 which is a popular stream cipher. Then using VBA on the programming side to show you guys how to change encrypted message content.

How to read a 24bits bitmap file

Hi Guys!
Bitmap (.bmp) files are digital image files that are easy to understand in terms of its byte to byte contents. Easy as its encode only the pixel in a format widely understood by many (I believe). The pixel encoding is in RGB format which stands for RED, GREEN and BLUE. In this blog, I'll show you guys how to read a .bmp file byte and byte using Excel Visual Basic for Application (VBA) with the help of windows API.

Basic Sending and reading data on Serial comport using VBA

Hi there! There are lots of electronic devices or modules that can be connected to computers or laptops and they are mapped as communication port/serial port or COM port... COM1,COM2, etc. The good example I have is the mbed NXP LPC1768 which is mapped as COM port once installed and connected to the computer via USB:

The Homing Device Project (Part I - The GPS Module)

I'm a comic book fan. Mostly in comic books, one gets to see technologies that are out of this world, like Iron Man's suit, the Fantastic Four's Ultimate Nullifier or Batman's Whirly-Bat. But one thing I don't get is why can't someone invent a "homing device" in real life up until now? Batman uses it all the time. Spider-man too in the form of a "Spider-tracer".

String Manipulation in Excel VBA

There are times when I'm building an electronics project with 1000+ components. I encoded my bill of materials (BOM) on excel. Say, 10K resistor for R1 to R5 so I put in there "Resistor 10K" then on "location" I will put "R1-5" or "R1-R5". This is good as it facilitates easy inputting of location without having to type "R1 R2 R3 R4 R5". So the BOM is completed in this way. Perfect! All in place. Later on, I want to know the value of say "R4" on my BOM containing 500+ different resistors. I search "R4"... only to know that excel cannot find the string "R4" because I did put R1-R5. This means there's really no "R4" at all.

The question now is how do I facilitate easy inputting of location without worrying that excel "find" cannot locate it? Probably excel vba can help solve this common pitfall. Well perfect! vba contains rich string manipulation that can solve this one.