Secure operating hour timer on cRIO 9066

[Raukho]

Hi,

as part of my work with the NI CompactRIO (cRIO), I recently decided to add an operating hour timer. Currently, I store the counter in a TDMS file on the cRIO, which works well for tracking purposes. However, there’s a challenge: I need to use WebDAV for user access, but this means others could potentially modify the file.

My initial thought was to create a hybrid system, where the counter writes to the EEPROM every six hours. This way, if there’s an issue, I can cross-check the TDMS file with the EEPROM data and only risk losing a maximum of six hours. Unfortunately, I couldn’t find documentation for modifying EEPROM storage specifically on the cRIO 9066 model.

So now, I’m considering other approaches. Could I achieve this using Linux permissions to restrict access? Or perhaps implement a manipulation-detection system to identify unauthorized changes?

Thanks for any thoughts!

[JÞB]

Outside of using Write Only Memory (that is a joke) I can offer the following possible approaches:

• Obfuscate the data in the file e.g. write the data as plain ASCII then duplicate the string by adding 0x80 to each character. 
• Obfuscate the file extension,   Generally people will not save files with a strange extension like *.myfiletype even if any text editor can read it.
• Add a data integrity hash to the file data.  That works only for determining if someone broke into the file.
• Hide the file in an unusual location or even hide only a backup file that you DO NOT DOCUMENT
• Add access control to the file 
• Add a really large warning in the file in plain text e.g. "Any unauthorized modifications to this file will unleash a pack of rabid wolves in your Grandma's House!" Be prepared to train a rabid wolf pack.

There is no foolproof way to restrict file access.  You simply MUST out smart out or outlaw fools.