Purly an acedemic question. Truely.
I have a program that I have been asked to demo to compare to its competitor's tools, which I use frequently. When I was finished, I was farting around with the provided license file that determines the amount of time you have to demo the tool. Out of curiosity, I altered the date by a single day. I updated the license file in the appropriate path, and as I expected, it knew what I did. But how?
I added a space at the end of the last line, and no problem. Then I added a CR, and again, no problem. Finally, I added a random digit outside of the formatted data, and it got upset, like when I changed the date by a day. I should say that the file format is .ivi, but the formatting inside the file is that of XML. I am not a coder, and to the extent I dabble with coding, I certainly don't use Windows Studio, so maybe XML formatting in a .ivi file is normal. I am just curious how they are detecting the change. Some sort of checksum, I would guess, but not of the hash variety, as the license file contains unique hardware identification for my system along with my business information. Then what? Maybe a more traditional error correction? CRC, UByte/short/int with big and little endian? But would that not be visible in the Hex dump of the license file?
Anyway just curious. I have long been a lurker but never asked a question before, but thought maybe I would this time. Thanks for any insights.