Hello,

as a newby in OllyDbg crackercountry I like to find the CRC or checksum calculation that is done in some Windows .exe application before that application sends the data and calculated checksum to the serialport.

According tips like using 'CEiD' I found that the application is written in Visual C++.
I would like to find the address(es) in the executable where the serialport is called, probably using some 'FileWrite()' function in the source.

I allready found the repeating loop where data is transmitted but I need some help here.

Or is there someone who likes to crack it for me? ;-) (I don't think it's that much work for an expert)

All tips are welcome.

regards,

Henk

Perhaps you might actually want to READ THE FRIGGIN FAQ, like the BIG RED LETTERS advised you and as is written under your signature. This is not a place where you get to ask people to "crack it for me." Had you taken the time to read the FAQ, you would know that already.

What WE expect here, is that YOU do YOUR homework and SHOW US that you have actually done it and when you need a "little" help, and have actually done your own searching for the answer, THEN you come here and ask for some help.

Now go actually read the FAQ!

Regards,

Sends the data to the serial port? What kind of program is it?

It's a program that sends program data by the serialport using infrared signals to a small robot to be flashed into that robots Atmega8L microcontroller and I want to make my own application that will do the flashing without having to use that special flash utility.

Right, so you don't want to crack the program as such, but rather reverse engineer the protocol, which you know includes some kind of checksum?

yep

It sounds like you need an API monitoring tool.