Encryption used derived from Blowfish. We use limited key sizes due to restrictions in our country.
Excel’s own password encryption based on AES can also be used.
Note that any application running offline can be cracked nowadays, but it is still not an easy task.
A hacker could in theory disassemble the EXE made with XLS Padlock to retrieve the different encryption keys, which are also different for each EXE and based on the application secret key you enter in XLS Padlock. But we ensured to make reverse engineering highly difficult by obfuscating a lot of our sensitive code, based on code virtualization (that means the sensitive pseudo-code is run by internal virtual machines and it is not in common pure assembler).
That’s the same technique as we use for our VBA compiler.
So, basically a hacker would have to study the different virtual machines in order to learn how they work before he could start understanding the original code.
That’s also why our EXE files are so large compared to the original workbook file.
Few “professional” hackers with very strong knowledge should still be able to crack the program, but they generally have more appealing challenges than cracking a secured workbook. Except if your workbook sells for millions, but in that case, you should look for another security solution than a mere 140 EUR solution.
In other terms, you should be OK for a very long time, but we cannot give you a 100% safety guarantee.
Just also search for “XLS Padlock crack” and you will only find hawks or disguised malware. It’s not that our software is not crackable, it’s just difficult to do it and, as said before, it requires time, knowledge and resources.