Many years ago I was a technician supporting a few custom programs on thousands of PCs. The developer of one of these programs had added a date check to his code so the program would refuse to run after a set date and each new release would increase this date by a few months so it would stop working after a few weeks if he ever stopped creating new releases. His contract ended and a few weeks later his software, now relied upon by hundreds of sites, stopped working. The contract for the software development was thoroughly checked and legal action against the developer was started but I asked to see if I could resolve the problem in the meantime.

It only took ten minutes with a dissassembler to find the JGT (Jump if greater than) and convert it to a JLT so the software would stop running if the date was before a certain date rather than after. I created a patching tool that simply flipped one bit that was sent out to all the sites and everything was good again. I don't think I'll ever beat the elegance of a single bit flip hack.

There's a lot of things going on that lead to this.

One, the developers spend more time running this code than we do, and they have to get the program working before we can even use it. So any parts of the program that are hostile to the developers risks killing the entire project. Obfuscating the copy protection can hit a point where it makes bug fixing difficult.

Two, lack of training. If you, me, and Steve each have a bag of tricks we all use to crack games, whichever one of us figures it out gets bragging rights but the game remains cracked. Meanwhile Developer Dan has to be aware of all the tricks in all of our bags together if he wants to keep the three of us out. Only there's not three of us, there's 300. Or today, probably more like 30,000.

Three, lack of motivation, which is itself several different situations. There's a certain amount of passive aggression you can put into a feature you don't even really want to work on. You can lean into any of the other explanations to defend why your code didn't protect from cracking all that much, but it's a checkbox that's trying to prove a negative, and nobody is going to give you any credit for getting it to work right in the same way they give you credit for fixing that corner glitch that the QA people keep bitching about. Or getting that particle animation to work that makes the AOE spells look badass.

Another method (much more common for software that asks for two pieces of information, like a name and a key) is to take a memdump of the process at the "your key is invalid" dialog, find the invalid key you just typed, and hope that a valid key is somewhere nearby in memory. Unlike the assembly trick, this requires 0 programming expertise beyond the ability to type `strings` on the command line.

This works because some programs use a hashing algorithm to calculate the key based on the name, do a strcmp, and pop a messagebox if the keys don't match, without zeroizing the valid key buffer first. If the key buffers are on the stack (or if the two mallocs just happen to use the same region in memory), it is often easy to find a valid key if you know where the invalid one is.

I guess software that derives keys this way is far less common than it once was, but I know of somebody who cracked something using this method just a few years ago, so it still pops up from time to time.

A certain automation system vendor uses proper USB license dongles in their PC software but they do not do challenge-response authentication. Instead they send a hardcoded string to the dongle and compare the response against a list that contains various software feature levels.

The whole automation system including machinery costs anywhere from 200k to 1M yet Vendor™ tries to milk the customers dry with a 1.5k software license that lets you manage up to 254 physically* connected systems. I'm pretty sure the license dongle is in reality designed to prevent casual tinkering of parameters, which is something only service techs should do.

*You can circumvent this with serial-over-Ethernet converters, which has resulted in an Industrial Internet of Shit-level security nightmare as companies happily expose their systems over the internet, thinking that license dongles are a substitute for authentication.

I remember I had some demo software that could be enabled with a code. I was just curious and at the code prompt, I entered the debugger. I dumped the process space and there was a nul-terminated string of letters and numbers. I restarted the process and entered them at the prompt and voila, it was enabled.

(I did go on to pay for the software)

I remember an icon editor (or something similar) for Windows 3.1, it was a shareware where you could enter a code to remove the nag screen. No crack was necessary, I basically managed to enter valid registration codes by just typing random numbers. In the end I had enough valid numbers that I could figure out the logic, it was something about the sums of digit groups.

I was wondering this actually, why not just skip past the check entirely instead of going through the effort to pass the check without the dongle?

> Many a crack back in the day was even more simple still, we'd just find and alter the right JE or JNE into a JMP and we're off to the races.

I did that with dBASE III, which used ProLok "laser protection" from Vault Corporation - a signature burned onto the diskette with a laser. Back then, I found it amazing that Ashton-Tate actually spent money to contract with a copy protection company for something that could be so easily defeated by a teenager reading assembler.

They could have easily just written the same kind of code themselves. An example of the power of marketing over substance.

I was able to replicate that protection mechanism just by scratching a diskette with a pin. The "laser" was a meaninglessly advanced-sounding solution that added no value compared to any other means of damaging a diskette.

Cracking is so fun because we have Slides!