问题
I have tried searching, and all questions are related to specific things like "how to generate key", and the like. Can anybody explain how different types of software activation work?
回答1:
In the most simplistic case, it is as maxwell5555 described. A registration code ("CD key") is sent to the user who enters it into the program or installer. The whole process can basically be done offline; the program itself locally determines that the code is valid or invalid.
This is nice and easy, but it extremely vulnerable to key sharing - since there's no "phoning home" then the application cannot know that thousands of different people are all using the same key that they got off the internet or a serial library or their friend. It's also reasonably easy to make "keygens" which generate valid-seeming keys that were never actually issued by the developers.
Then we get into online registration. You still have some kind of code, but the program will phone home back to the server to determine whether the code is valid and usually unique. This stops basic key sharing, because the company knows if too many people from all over the world are all using the same key. Perhaps there is some kind of indentification involved using MAC address, too, with infinte registrations allowed on the same hardware but maybe a limited number on what appears to be a different computer.
This is still pretty easy and stops simple key sharing. People will actually have to get into cracking the software or faking the server response to get past it.
Sometimes the program itself is partially/mostly encrypted and is only decrypted by the online registration step. Depending on how well this is obfuscated then it can be pretty difficult and time consuming to crack. Bioshock was a high-profile example of this - debuting with a brand new encryption/copy protection scheme that took around two weeks from release to be broken.
Finally, a particularly guarded applciation might stay in constant contact with the server, refusing to work at all if the connection is severed. In this case to get arouind the activation you need to fake the server itself. Steam emulators and private WoW servers are an example of this.
And in the end, nothing is uncrackable.
回答2:
I suspect a lot of the implementers will not give this information out because it opens them to hacking. But if I were to do this, this is how I would go about it:
- Decide if the software is licensed to a person or a computer.
- Find a way of identifying the person/computer (login account or ID from the computer hardware).
- On request/payment: in your private database, create a licence key and add an entry for the person/PC with this key.
- Provide the client software with the key.
- Your software either stores the key locally, or regularly checks for the key giving a service of yours the identifying information in return for which your service supplies the key if there is one. If none is found, your software offers them details to purchase a licence. The latter allows for floating keys, computer upgrades, and identifying duplicate installations.
Is that what you were asking for?
回答3:
A common, simple way of implementing software activation/registration is to create a license algorithm. For example, lets say I have some shareware I want to protect and when someone gives me money, I send them a 4-byte registration code. I could build the algorithm into my shareware such that it validates the code the users enters. My algorithm would be as follows:
1) Byte0 * Byte1 = 6
2) Byte2 - Byte3 = 1
3) Byte0 + Byte2 = 8
Two possible valid codes are:
3254
1676
When the user enters a valid code, the software unlocks its regular functionality by setting a flag somewhere. Obviously, this is an extremely simplistic example. Registration validation algorithms can be as complex as you want.
You can also perform this registration over the internet to protect your validation algorithm from reverse engineering, and keep people from sharing keys. No validation scheme is perfect though.
来源：https://stackoverflow.com/questions/1875047/how-does-software-activation-work