This is a problem we all have to consider at some point.
After many years and many approaches I tend to agree in general with the staterment:
"For any protected software used by more than a few hundred people, you can find a cracked version. So far, every protection scheme can be tampered with."
Does your employer enforce the use of anti-piracy software?
Further, every time I post about this subject, some one will remind me;
"First of all, no matter what kind of protection you'll employ,a truly dedicated cracker will, eventually, get through all of the protective barriers."
What's the best value for money c# code protection for a single developer
So not withstanding these two broadly true disclaimers, lets talk about "protection"!
I still feel that for smaller apps that are unlikely to warrent the time and attention of a skilled cracker, protection IS a worthwhile exercise.
It seems obvious that no matter what you do, if the cracker can switch the outcome of an IF statement (jmp) by patching the application, then all the passwords and dongles in the world anre not going to help.
So My approach has been to obfuscate the code with virtualization using products like:
http://www.oreans.com/codevirtualizer.php
I have been very happy with this product. To my knowledge it has neve been defeated.
I can even compress the executable with PEcompact
Does anyone else have experience with it?
Had nothing but problems with EXEcryptor
http://www.strongbit.com/news.asp
Even the site is a headache to use.
The compiled apps would crash when doing any WMI calls.
This approach allows you to surround smaller sections of code with the obfuscation and thus protect the security checking etc.
I Use the online authorization approach, as the application needs data from the server regularly so it makes no sense for the user to use it off line for extended periods. By definition, the app is worthless at that point, even if it is cracked.
So a simple encrypted handshake is plenty good. I just check it occasionally within the obfuscation protection. If the user installs the app on a different machine, a New ID is uploaded upon launch and the server disables the old ID and returns a new authorization.
I also use a hash of the compiled app and check it at launch to see if a single bit has changed, then open the app as a file (with a read LOCK) from within the app to prevent anyone changing it once launched.
Since all static strings are clearly visible in the .exe file, I try to be generic with error messages and so forth. You will not find the string "Authorization failed" anywhere.
To protect against memory dumps, I use a simple text obfuscation technique (like XOR every character) This makes plain text data in memory harder to distinguish from variables and so forth.
Then of course there is AES for any data that is really sensitive. I like counter mode for text as this results in no repeating sequences revealing underlying data like a sequence of white spaces.
But with all these techniques, if the Key or Initialization vector can be dumped from memory, or the IF statement bypassed, everything is wasted.
I tend to use a switch statement rather than a conditional statement. Then I create a second function that is basically a dead end instead of the function that actually performs the desired task.
Another idea is to code pointers with a variable added. The variable is the result of the authorization (usually zero). This will inevitable lead to a GPF at some point.
I only use this as a last resort after a few lower level authorizations have failed otherwise real users may encounter it. Then the reputation of your software is lowered.
What techniques do you use?
(this is NOT a thread debating the merits of implementing something. It is designed for those that have decided to do SOMETHING)
I disagree xsl.
We protect our code, not because we want to protect our revenue - we accept that those who would use if without a license probably would never pay for it anyway.
Instead, we do it to protect the investment our customers have made in our software. We believe that the use of our software makes them more competative in their market place and that if other companies have access to it without paying they have an unfair advantage - ie, they become as competative without having the overhead of the licensing cost.
We are very careful to ensure that the protection - which is home grown - is as unobtrusive as possible to the valid users, and to this end we would never consider 'buying in' an off the shelf solution that may impact this.
You don't need a few hundred users to get your software cracked. I got annoyed at having my shareware cracked so many times, so as an experiment I created a program called Magic Textbox (which was just a form with a textbox on it) and released it to shareware sites (it had its own PAD file and everything). A day later a cracked version of Magic Textbox was available.
This experience made me pretty much give up trying to protect my software with anything more than rudimentary copy protection.
I personally use the code techniques discussed here. These tricks have the benefit of inconveniencing pirates without making life more difficult for your legitimate end-users
But the more interesting question isn't "what", but "why". Before a software vendor embarks on this type of exercise, it's really important to build a threat model. For example, the threats for a low-priced B2C game are entirely different to those for a high-value B2B app.
Patrick Mackenzie has a good essay where he discusses some of the threats, including an analysis of 4 types of potential customer. I recommend doing this threat analysis for your own app before making choices about protecting your business model.
I've implemented hardware keying (dongles) before myself, so I'm not totally unfamiliar with the issues. In fact, I've given it a great deal of thought. I don't agree with anyone violating copyright law, as your crackers are doing. Anyone who doesn't want to legally aquire a copy of your software should do without. I don't ever violate software copyright myself. That being said...
I really, really dislike the word "protect" used here. The only thing you are trying to protect is your control. You are not protecting the software. The software is just fine either way, as are your users.
The reason that keeping people from copying and sharing your software is such an unholy PITA is that preventing such activites is unnatural. The whole concept of a computer revolves around copying data, and it is simple human nature to want to share useful things. You can fight these facts if you really insist, but it will be a lifelong fight. God isn't making humans any differently, and I'm not buying a computer that can't copy things. Perhaps it would be better to find some way to work with computers and people, rather than fighting against them all the time?
I, along with the majority of professional software developers, am employed full time by a company that needs software developed so that it can do its business, not so it can have a "software product" with artificial scarcity to "sell" to users. If I write something generally useful (that isn't considered a "competive advantage" here), we can release it as Free Software. No "protection" is needed.
From some of the links:
The concept I tried to explain is what I call the “crack spread”. It doesn’t matter that a crack (or keygen, or pirated serial, or whatever) exists for your application. What matters is how many people have access to the crack.
Where/when to check the serial number: I check once on startup. A lot of people say “Check in all sorts of places”, to make it harder for someone to crack by stripping out the check. If you want to be particularly nasty to the cracker, check in all sorts of places using inlined code (i.e. DON’T externalize it all into SerialNumberVerifier.class) and if at all possible make it multi-threaded and hard to recognize when it fails, too. But this just makes it harder to make the crack, not impossible, and remember your goal is generally not to defeat the cracker. Defeating the cracker does not make you an appreciable amount of money. You just need to defeat the casual user in most instances, and the casual user does not have access to a debugger nor know how to use one.
If you’re going to phone home, you should be phoning home with their user information and accepting the serial number as the output of your server’s script, not phoning home with the serial number and accepting a boolean, etc, as the output. i.e. you should be doing key injection, not key verification. Key verification has to ultimately happen within the application, which is why public key crypto is the best way to do it. The reason is that the Internet connection is also in the hands of the adversary :) You’re a hosts file change away from a break-once, break-everywhere exploit if your software is just expecting to read a boolean off the Internet.
Do not make an “interesting” or “challenging” protection. Many crackers crack for the intellectual challenge alone. Make your protection hard to crack but as boring as possible.
There are some cracks which search for byte patterns in search for the place to patch. They usually aren’t defeated by a recompile, but if your .EXE is packed (by ASProtect, Armadillo, etc) these kind of cracks must first unpack the .EXE.. and if you use a good packer such as ASProtect, the cracker will be able to unpack the EXE manually using an assembly level debugger such as SoftICE, but won’t be able to create a tool which unpacks the .EXE automatically (to apply the byte patches afterwards).
I have used .NET Reactor in the past with good results - http://www.eziriz.com/
What I liked about this product is that it did not require you to obfuscate the code in order to have pretty good protection.
xsl, that is a very narrow point of view with MANY built in assumtions.
It seems obvious to me that any app that relies on delivering something from a server under your control should be able to do a fairly good job of figuring our who has a valid account!
I am also of the belief that regular updates (meaning a newly compiled app with code in different locations) will make cracked vesrions obsolete quickly. If your app communicates with a server, launching a secondary process to replace the main executable every week is a piece of cake.
So yes, nothing is uncrackable, but with some clever intrinsic design, it becomes a moot point. The only factor that is significant is how much time are the crackers willing to spend on it, and how much effort are your potential customers willing to exert in trying to find the product of their efforts on a weekly or even daily basis!
I suspect that if your app provides a usefull valuable function then they will be willing to pay a fair price for it. If not, Competitive products will enter the market and your problme just solved itself.
Related
I'm trying to figure out how to properly fill in PCI SAC D compliance form for a startup business with the only one owner/architect/developer/admin/QA/etc - all of them is me alone.
It's a web app for selling a particular intangible service. No card information is going to be stored. The reason for SAC D - I'd prefer to do some validation logic on my server side and have a total review and confirmation page that match the rest of UI.
Hosting environment will be AWS Beanstalk + RDS.
When I read it, common sense tells me to ignore statements like "Interview personnel" or "Review policies & procedures", but I expect that large corporate minds are not usually driven by common sense but by rules.
I can hardly imaging formal process of interviewing myself and documenting what I've asked and what I've said, especially the benefits of doing that.
Most of the questions in Requirement 8 make no sense either.
Questions that assume that stuff is more then one employee make no sense.
Can those be skipped (N/A-ed) or should I formally do the exercise and generate some funny nonsense?
Thank you!
You can N/A those questions.
Remember the SAQ is a SELF Assessment Questionnaire, not a test you are taking. The payment card industry is more concerned about your adherence to the "spirit" of PCI-DSS rather than hard fast rules. It's more about protecting cardholder data than it is complying with things that don't apply to your case. (Although anything that does apply should definitely be followed as a hard rule.)
If you did get audited, it would probably only be because you had a breach, which obviously would NOT be because you didn't "interview yourself" and put on a security ID badge when you sat down in front of your development computer :-D and I don't think you'd have any trouble at all getting that point across to the QSA.
Now, having all your security policies and procedures, network diagrams, firewall, etc. documented and reviewed periodically does apply, since for security guidelines to be followed on a continual basis, they must be reviewed on a continual basis. For these, just use common sense. In other words, go over your firewall rules and such at least as often as PCI-DSS requires and ask yourself, "Do I still need this ALLOW SNMP port 161 rule to be in effect?" etc. etc...Oh dear I think I just told you to interview yourself... :-D
Anyway, you get the idea.
Are you really really sure you need SAQ D? It's a pretty big undertaking if you're starting from scratch. Is the money flowing into your merchant account? If so you could potentially get away with SAQ A which is going to make your life WAY easier. If not, then you're probably SAQ D service provider and you'll have no choice but to do SAQ D. In terms of styling and validation you could use an iFrame solution like Braintree, you have quite a lot of control and it reduces your PCI scope significantly.
In my experience talking with the bank that holds the merchant account is a good place to start, they're keen for secure systems to be developed, so are likely to give you advice on what you need to do. You could also engage a QSA but they are not cheap in general.
I don't think (though i'm not 100% sure) interviewing yourself is required, those instructions are for auditors to use to ensure that policy and procedures are being followed. For lone developers, a big problem is code reviews, you will need someone else to do that.
I'm developing an app that manages sensitive information. For this reason I would like to give the user the option of creating a password to encrypt the data. This information is only to be saved in the device; the idea is not to encrypt and send the data through a network, but to prevent other people with total access to the device to have access to it.
Now, what I don't know is if I should encrypt the whole data base or encrypt only each entry before saving it. What is the recommended approach to encrypt data bases?
Diego,
Encrypting data is a subtle problem.
First, do the easy stuff. Turn on Apple's file security. That will probably give you more security for less effort than anything you can write. It probably provides all of the security you really need on the device. If it doesn't, you should know exactly what it doesn't provide. That would be the main cause for writing special purpose code. Apple recently posted an excellent white paper on iOS security. We all should read it.
Second, security is broken in subtle and non-obvious ways. It just isn't a matter of firing up the encryption and then hoping for the best. How are you going to handle key distribution to other devices? How are you going to handle lost keys? Do you trust Apple's keychain? (Have they fixed their process in the wake of "goto fail;"?)
The way most security folks I know handle these issues is by building detailed scenarios of use. And then implementing code to see if the design is any good. Then asking their friends and consultants to poke holes in the design; fix the holes until you have "confidence" in your design. If you are new to security, and by the nature of your question I assume you are relatively new to the field, then you should NOT have confidence in your design. You now need to reimplement your design with simpler code and simpler processes. Then put it in front of real users. They will show you how your security process fails in real hands. Bad security design has killed many products and it can kill yours.
I would be very careful. Use what Apple has already carefully engineered. Seriously ask yourself if you need more than that. Ask your management how much they want to spend on security? Ask your users how important the bother of security is for them? I suspect the answer to both questions is: no, they do not want to pay for or bother with security.
As a result, do the simple stuff: use Apple's iOS security.
Anon,
Andrew
I'm about to get finished developing a windows application which I want to release as shareware. It was developed in C# and will be running on .Net 3.5+ machines.
To use it the user will have to be online.
My intent is to let the user try it for 30 days and then limit its functionality until a registration is purchased.
The installer will be made available via an msi file.
Could anyone give the general steps on how to implement this?
Here are some more specific questions:
Since I am trying to avoid having to invest a lot upfront in order to establish an e-commerce site, I was thinking of a way to just let the user pay somehow, while supplying his email in which he then receives the unlock key.
I found some solutions out there like listed here:
Registration services
I am still not sure, if they are the way to go.
One of my main concerns is to prevent the reuse if a given serial, e.g. if two users run the program with the same serial at the same time, this serial should disabled or some other measure be taken.
Another point is, that my software could potentially be just copied from one computer to the other without using an installer, so to just protect the installer itself will not be sufficient.
Maybe someone who already went though this process can give me some pointers, like the general steps involved (like 1. Get domain, 2. Get certain kind of webhost ....) and address some of the issues I mentioned above.
I'm thankful for any help people can give me.
I don't have a useful answer for you, but I did have a couple observations I wanted to share that were too large to fit in a comment. Hopefully someone else with more technical expertise can fill in the details.
One of my main concerns is to prevent the reuse if a given serial, e.g. if two users run the program with the same serial at the same time, this serial should disabled or some other measure be taken.
To ensure that two people aren't using the same serial number, your program will have to "phone home." A lot of software does this at installation time, by transmitting the serial number back to you during the installation process. If you want to do it in real time, your application will have to periodically connect to your server and say "this serial number is in use."
This is not terribly user friendly. Any time that the serial number check is performed, the user must be connected to the Internet, and must have their firewall configured to allow it. It also means that you must commit to maintaining the server side of things (domain name, server architecture) unchanged forever. If your server goes down, or you lose the domain, your software will become inoperative.
Of course, if a connection to your service specifically (rather than the Internet in general) is essential to the product's operation, then it becomes a lot easier and more user friendly.
Another point is, that my software could potentially be just copied from one computer to the other without using an installer, so to just protect the installer itself will not be sufficient.
There are two vectors of attack here. One is hiding a piece of information somewhere on the user's system. This is not terribly robust. The other is to check and encode the user's hardware configuration and encode that data somewhere. If the user changes their hardware, force the product to reactivate itself (this is what Windows and SecuROM do).
As you implement this, please remember that it is literally impossible to prevent illegal copying of software. As a (presumably) small software developer, you need to balance the difficulty to crack your software against the negative effects your DRM imposes on your users. I personally would be extremely hesitant to use software with the checks that you've described in place. Some people are more forgiving than I am. Some people are less so.
The energy and effort to prevent hacks from breaking your code is very time consuming. You'd be better served by focusing on distribution and sales.
My first entry into shareware was 1990. Back then the phrase was S=R which stood for Shareware equals Registered. A lot has changed since then. The web is full of static and you have to figure out how to get heard above the static.
Here's somethings I've learned
Don't fall in love with your software. Someone will always think it should work differently. Don't try and convert them to your way of thinking instead listen and build a list of enhancements for the next release.
Learn how to sell or pay someone to help you sell your stuff
Digital River owns most of the registration companies out there
Create free loss leaders that direct traffic back to you
Find a niche that is has gone unmet and fill it
Prevent copying: base the key on the customer's NIC MAC. Most users will not go to the trouble of modifying their NIC MAC. Your app will have a dialog to create and send the key request, including their MAC.
The open issue is that many apps get cracked and posted to warez sites. Make this less likely by hiding the key validation code in multiple places in your app. Take care to treat honest users with respect, and be sure your key validation does not annoy them in any way.
Make it clear that the key they are buying is node locked.
And worry about market penetration. Get a larger installed base by providing a base product that has no strings attached.
cheers -- Rick
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I wrote a utility for photographers that I plan to sell online pretty cheap ($10). I'd like to allow the user to try the software out for a week or so before asking for a license. Since this is a personal project and the software is not very expensive, I don't think that purchasing the services of professional licensing providers would be worth it and I'm rolling my own.
Currently, the application checks for a registry key that contains an encrypted string that either specifies when the trial expires or that they have a valid license. If the key is not present, a trial period key is created.
So all you would need to do to get another week for free is delete the registry key. I don't think many users would do that, especially when the app is only $10, but I'm curious if there's a better way to do this that is not onerous to the legitimate user. I write web apps normally and haven't dealt with this stuff before.
The app is in .NET 2.0, if that matters.
EDIT: You can make your current licensing scheme considerable more difficult to crack by storing the registry information in the Local Security Authority (LSA). Most users will not be able to remove your key information from there. A search for LSA on MSDN should give you the information you need.
Opinions on licensing schemes vary with each individual, more among developers than specific user groups (such as photographers). You should take a deep breath and try to see what your target user would accept, given the business need your application will solve.
This is my personal opinion on the subject. There will be vocal individuals that disagree.
The answer to this depends greatly on how you expect your application to be used. If you expect the application to be used several times every day, you will benefit the most from a very long trial period (several month), to create a lock-in situation. For this to work you will have to have a grace period where the software alerts the user that payment will be needed soon. Before the grace period you will have greater success if the software is silent about the trial period.
Wether or not you choose to believe in this quite bold statement is of course entirely up to you. But if you do, you should realize that the less often your application will be used, the shorter the trial period should be. It is also very important that payment is very quick and easy for the user (as little data entry and as few clicks as possible).
If you are very uncertain about the usage of the application, you should choose a very short trial period. You will, in my experience, achieve better results if the application is silent about the fact that it is in trial period in this case.
Though effective for licensing purposes, "Call home" features is regarded as a privacy threat by many people. Personally I disagree with the notion that this is any way bad for a customer that is willing to pay for the software he/she is using. Therefore I suggest implementing a licensing scheme where the application checks the license status (trial, paid) on a regular basis, and helps the user pay for the software when it's time. This might be overkill for a small utility application, though.
For very small, or even simple, utility applications, I argue that upfront payment without trial period is the most effective.
Regarding the security of the solution, you have to make it proportional to the development effort. In my line of work, security is very critical because there are partners and dealers involved, and because the investment made in development is very high. For a small utility application, it makes more sense to price it right and rely on the honest users that will pay for the software that address their business needs.
There's not much point to doing complicated protection schemes. Basically one of two things will happen:
Your app is not popular enough, and nobody cracks it.
Your app becomes popular, someone cracks it and releases it, then anybody with zero knowledge can simply download that crack if they want to cheat you.
In the case of #1, it's not worth putting a lot of effort into the scheme, because you might make one or two extra people buy your app. In the case of #2, it's not worth putting a lot of effort because someone will crack it anyway, and the effort will be wasted.
Basically my suggestion is just do something simple, like you already are, and that's just as effective. People who don't want to cheat / steal from you will pay up, people who want to cheat you will do it regardless.
If you are hosting your homepage on a server that you control, you could have the downloadable trial-version of your software automatically compile to a new binary every night. This compile will replace a hardcoded datetime-value in your program for when the software expires. That way the only way to "cheat" is to change the date on your computer, and most people wont do that because of the problems that will create.
Try the Shareware Starter Kit. It was developed my Microsoft and may have some other features you want.
http://msdn.microsoft.com/en-us/vs2005/aa718342.aspx
If you are planning to continue developing your software, you might consider the ransom model:
http://en.wikipedia.org/wiki/Street_Performer_Protocol
Essentially, you develop improvements to the software, and then ask for a certain amount of donations before you release them (without any DRM).
One way to do it that's easy for the user but not for you is to hard-code the expiry date and make new versions of the installer every now and then... :)
If I were you though, I wouldn't make it any more advanced than what you're already doing. Like you say it's only $10, and if someone really wants to crack your system they will do it no matter how complicated you make it.
You could do a slightly more advanced version of your scheme by requiring a net connection and letting a server generate the trial key. If you do something along the lines of sign(hash(unique_computer_id+when_to_expire)) and let the app check with a public key that your server has signed the expiry date it should require a "real" hack to bypass.
This way you can store the unique id's serverside and refuse to generate a expiry date more than once or twice. Not sure what to use as the unique id, but there should be some way to get something useful from Windows.
I am facing the very same problem with an application I'm selling for a very low price as well.
Besides obfuscating the app, I came up with a system that uses two keys in the registry, one of which is used to determine that time of installation, the other one the actual license key. The keys are named obscurely and a missing key indicates tampering with the installation.
Of course deleting both keys and reinstalling the application will start the evaluation time again.
I figured it doesn't matter anyway, as someone who wants to crack the app will succeed in doing so, or find a crack by someone who succeeded in doing so.
So in the end I'm only achieving the goal of making it not TOO easy to crack the application, and this is what, I guess, will stop 80-90% of the customers from doing so. And afterall: as the application is sold for a very low price, there's no justification for me to invest any more time into this issue than I already have.
just be cool about the license. explain up front that this is your passion and a child of your labor. give people a chance to do the right thing. if someone wants to pirate it, it will happen eventually. i still remember my despair seeing my books on bittorrent, but its something you have to just deal with. Don't cave to casual piracy (what you're doing now sounds great) but don't cripple the thing beyond that.
I still believe that there are enough honest people out there to make a for-profit coding endeavor worth while.
Don't have the evaluation based on "days since install", instead do number of days used, or number of times run or something similar. People tend to download shareware, run it once or twice, and then forget it for a few weeks until they need it again. By then, the trial may have expired and so they've only had a few tries to get hooked on using your app, even though they've had it installed for a while. Number of activation/days instead lets them get into a habit of using your app for a task, and also makes a stronger sell (i.e. you've used this app 30 times...).
Even better, limiting the features works better than timing out. For example, perhaps your photography app could limit the user to 1 megapixel images, but let them use it for as long as they want.
Also, consider pricing your app at $20 (or $19.95). Unless there's already a micropayment setup in place (like iPhone store or XBoxLive or something) people tend to have an aversion to buying things online below a certain price point (which is around $20 depending on the type of app), and people assume subconciously if something is inexpensive, it must not be very good. You can actually raise your conversion rate with a higher price (up to a point of course).
In these sort of circumstances, I don't really think it matters what you do. If you have some kind of protection it will stop 90% of your users. The other 10% - if they don't want to pay for your software they'll pretty much find a way around protection no matter what you do.
If you want something a little less obvious you can put a file in System32 that sounds like a system file that the application checks the existence of on launch. That can be a little harder to track down.
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My company is looking to start distributing some software we developed and would like to be able to let people try the software out before buying. We'd also like to make sure it can't be copied and distributed to our customers' customers.
One model we've seen is tying a license to a MAC address so the software will only work on one machine.
What I'm wondering is, what's a good way to generate a license key with different information embedded in it such as license expiration date, MAC address, and different software restrictions?
I've used both FLEXlm from Macrovision (formerly Globetrotter) and the newer RLM from Reprise Software (as I understand, written by FlexLM's original authors). Both can key off either the MAC address or a physical dongle, can be either node-locked (tied to one machine only) or "floating" (any authorized machine on the network can get a license doled out by a central license server, up to a maximum number of simultaneously checked-out copies determined by how much they've paid for). There are a variety of flexible ways to set it up, including expiration dates, individual sub-licensed features, etc. Integration into an application is not very difficult. These are just the two I've used, I'm sure there are others that do the job just as well.
These programs are easily cracked, meaning that there are known exploits that let people either bypass the security of your application that uses them, either by cutting their own licenses to spoof the license server, or by merely patching your binary to bypass the license check (essentially replacing the subroutine call to their library with code that just says "return 'true'". It's more complicated than that, but that's what it mostly boils down to. You'll see cracked versions of your product posted to various Warez sites. It can be very frustrating and demoralizing, all the more so because they're often interested in cracking for cracking sake, and don't even have any use for your product or knowledge of what to do with it. (This is obvious if you have a sufficiently specialized program.)
Because of this, some people will say you should write your own, maybe even change the encryption scheme frequently. But I disagree. It's true that rolling your own means that known exploits against FLEXlm or RLM won't instantly work for your application. However, unless you are a total expert on this kind of security (which clearly you aren't or you wouldn't be asking the question), it's highly likely that in your inexperience you will end up writing a much less secure and more crackable scheme than the market leaders (weak as they may be).
The other reason not to roll your own is simply that it's an endless cat and mouse game. It's better for your customers and your sales to put minimal effort into license security and spend that time debugging or adding features. You need to come to grips with the licensing scheme as merely "keeping honest people honest", but not preventing determined cracking. Accept that the crackers wouldn't have paid for the software anyway.
Not everybody can take this kind of zen attitude. Some people can't sleep at night knowing that somebody somewhere is getting something for nothing. But try to learn to deal with it. You can't stop the pirates, but you can balance your time/effort/expense trying to stop all piracy versus making your product better for users. Remember, sometimes the most pirated applications are also the most popular and profitable. Good luck and sleep well.
I'd suggest you take the pieces of information you want in the key, and hash it with md5, and then just take the first X characters (where X is a key length you think is manageable).
Cryptographically, it's far from perfect, but this is the sort of area where you want to put in the minimum amount of effort which will stop a casual attacker - anything more quickly becomes a black hole.
Oh, I should also point out, you will want to provide the expiration date (and any other information you might want to read out yourself) in plain text (or slightly obfuscated) as part of the key as well if you go down this path - The md5 is just to stop the end user from changing he expiration date to extend the license.
The easiest thing would be a key file like this...
# License key for XYZZY
expiry-date=2009-01-01
other-info=blah
key=[md5 has of MAC address, expiry date, other-info]
We've used the following algorithm at my company for years without a single incident.
Decide the fields you want in the code. Bit-pack as much as possible. For example, dates could be "number of days since 2007," and then you can get away with 16-bits.
Add an extra "checksum" field. (You'll see why in a second.) The value of this field is a checksum of the packed bytes from the other fields. We use "first 32 bits from MD5."
Encrypt everything using TEA. For the key, use something that identifies the customer (e.g. company name + personal email address), that way if someone wants to post a key on the interweb they have to include their own contact info in plain text.
Convert hex to a string in some sensible way. You can do straight hex digits but some people like to pick a different set of 16 characters to make it less obvious. Also include dashes or something regularly so it's easier to read it over the phone.
To decrypt, convert hex to string and decrypt with TEA. But then there's this extra step: Compute your own checksum of the fields (ignoring the checksum field) and compare to the given checksum. This is the step that ensures no one tampered with the key.
The reason is that TEA mixes the bits completely, so if even one bit is changed, all other bits are equally likely to change during TEA decryption, therefore the checksum will not pass.
Is this hackable? Of course! Almost everything is, but this is tight enough and simple to implement.
If tying to contact information is not sufficient, then include a field for "Node ID" and lock it to MAC address or somesuch as you suggest.
Don't use MAC addresses. On some hardware we've tested - in particular some IBM Thinkpads - the MAC address can change on a restart. We didn't bother investigating why this was, but we learned quite early during our research not to rely on it.
Obligatory disclaimer & plug: the company I co-founded produces the OffByZero Cobalt licensing solution. So it probably won't surprise you to hear that I recommend outsourcing your licensing, & focusing on your core competencies.
Seriously, this stuff is quite tricky to get right, & the consequences of getting it wrong could be quite bad. If you're low-volume high-price a few pirated copies could seriously dent your revenue, & if you're high-volume low-price then there's incentive for warez d00dz to crack your software for fun & reputation.
One thing to bear in mind is that there is no such thing as truly crack-proof licensing; once someone has your byte-code on their hardware, you have given away the ability to completely control what they do with it.
What a good licensing system does is raise the bar sufficiently high that purchasing your software is a better option - especially with the rise in malware-infected pirated software. We recommend you take a number of measures towards securing your application:
get a good third-party licensing system
pepper your code with scope-contained checks (e.g. no one global variable like fIsLicensed, don't check the status of a feature near the code that implements the feature)
employ serious obfuscation in the case of .NET or Java code
The company I worked for actually used a usb dongle. This was handy because:
Our software was also installed on that USB Stick
The program would only run if it found the (unique) hardware key (any standard USB key has that, so you don't have to buy something special, any stick will do)
it was not restricted to a computer, but could be installed on another system if desired
I know most people don't like dongles, but in this case it was quite handy as it was actually used for a special purpose media player that we also delivered, the USB keys could thus be used as a demo on any pc, but also, and without any modifications, be used in the real application (ie the real players), once the client was satisfied
We keep it simple: store every license data to an XML (easy to read and manage), create a hash of the whole XML and then crypt it with a utility (also own and simple).
This is also far from perfect, but it can hold for some time.
Almost every commercial license system has been cracked, we have used many over the years all eventually get cracked, the general rule is write your own, change it every release, once your happy try to crack it yourself.
Nothing is really secure, ultimately look at the big players Microsoft etc, they go with the model honest people will pay and other will copy, don't put too much effort into it.
If you application is worth paying money for people will.
I've used a number of different products that do the license generation and have created my own solution but it comes down to what will give you the most flexibility now and down the road.
Topics that you should focus on for generating your own license keys are...
HEX formating, elliptic curve cryptography, and any of the algorithms for encryption such as AES/Rijndael, DES, Blowfish, etc. These are great for creating license keys.
Of course it isn't enough to have a key you also need to associate it to a product and program the application to lock down based on a key system you've created.
I have messed around with creating my own solution but in the end when it came down to making money with the software I had to cave and get a commercial solution that would save me time in generating keys and managing my product line...
My favorite so far has been License Vault from SpearmanTech but I've also tried FlexNet (costly), XHEO (way too much programming required), and SeriousBit Ellipter.
I chose the License Vault product in the end because I would get it for much cheaper than the others and it simply had more to offer me as we do most of our work in .NET 3.5.
It is difficult to provide a good answer without knowing anything about your product and customers. For enterprise software sold to technical people you can use a fairly complex licensing system and they'll figure it out. For consumer software sold to the barely computer-literate, you need a much simpler system.
In general, I've adopted the practice of making a very simple system that keeps the honest people honest. Anyone who really wants to steal your software will find a way around any DRM system.
In the past I've used Armadillo (now Software Passport) for C++ projects. I'm currently using XHEO for C# projects.
If your product requires the use of the internet, then you can generate a unique id for the machine and use that to check with a license web service.
If it does not, I think going with a commercial product is the way to go. Yes, they can be hacked, but for the person who is absolutely determined to hack it, it is unlikely they ever would have paid.
We have used: http://www.aspack.com/asprotect.aspx
We also use a function call in their sdk product that gives us a unique id for a machine.
Good company although clearly not native English speakers since their first product was called "AsPack".