I'm currently involved in developing a product (developed in C#) that'll be available for downloading and installing for free but in a very limited version. To get access to all the features the user has to pay a license fee and receive a key. That key will then be entered into the application to 'unlock' the full version.
Keygen means a small program that will generate a cd key, serial number, activation number, license code or registration number for a piece of software. Keygen is short for Key Generator. A keygen is made available through crack groups for free download. How do i create and code a product key into my c# App. Visual Studio Languages. Then you will use the Serial Maker to make a serial key (password.
As using a license key like that is kind of usual I'm wondering :
- How's that usually solved?
- How can I generate the key and how can it be validated by the application?
- How can I also avoid having a key getting published on the Internet and used by others that haven't payed the license (a key that basically isn't 'theirs').
I guess I should also tie the key to the version of application somehow so it'll be possible to charge for new keys in feature versions.
Anything else I should think about in this scenario?
Robert Harvey♦15 Answers
Caveat: you can't prevent users from pirating, but only make it easier for honest users to do the right thing.
Windows 10 enterprise activation serial key. Assuming you don't want to do a special build for each user, then:
- Generate yourself a secret key for the product
- Take the user's name
- Concatentate the users name and the secret key and hash with (for example) SHA1
- Unpack the SHA1 hash as an alphanumeric string. This is the individual user's 'Product Key'
- Within the program, do the same hash, and compare with the product key. If equal, OK.
But, I repeat: this won't prevent piracy
Serial Key Generator Online
I have recently read that this approach is not cryptographically very sound. But this solution is already weak (as the software itself has to include the secret key somewhere), so I don't think this discovery invalidates the solution as far as it goes.
Just thought I really ought to mention this, though; if you're planning to derive something else from this, beware.
Steven A. LoweThere are many ways to generate license keys, but very few of those ways are truly secure. And it's a pity, because for companies, license keys have almost the same value as real cash.
Ideally, you would want your license keys to have the following properties:
Only your company should be able to generate license keys for your products, even if someone completely reverse engineers your products (which WILL happen, I speak from experience). Obfuscating the algorithm or hiding an encryption key within your software is really out of the question if you are serious about controlling licensing. If your product is successful, someone will make a key generator in a matter of days from release.
A license key should be useable on only one computer (or at least you should be able to control this very tightly)
A license key should be short and easy to type or dictate over the phone. You don't want every customer calling the technical support because they don't understand if the key contains a 'l' or a '1'. Your support department would thank you for this, and you will have lower costs in this area.
So how do you solve these challenges ?
The answer is simple but technically challenging: digital signatures using public key cryptography. Your license keys should be in fact signed 'documents', containing some useful data, signed with your company's private key. The signatures should be part of the license key. The product should validate the license keys with the corresponding public key. This way, even if someone has full access to your product's logic, they cannot generate license keys because they don't have the private key. A license key would look like this: BASE32(CONCAT(DATA, PRIVATE_KEY_ENCRYPTED(HASH(DATA))))The biggest challenge here is that the classical public key algorithms have large signature sizes. RSA512 has an 1024-bit signature. You don't want your license keys to have hundreds of characters.One of the most powerful approaches is to use elliptic curve cryptography (with careful implementations to avoid the existing patents). ECC keys are like 6 times shorter than RSA keys, for the same strength. You can further reduce the signature sizes using algorithms like the Schnorr digital signature algorithm (patent expired in 2008 - good :) )
This is achievable by product activation (Windows is a good example). Basically, for a customer with a valid license key, you need to generate some 'activation data' which is a signed message embedding the computer's hardware id as the signed data. This is usually done over the internet, but only ONCE: the product sends the license key and the computer hardware id to an activation server, and the activation server sends back the signed message (which can also be made short and easy to dictate over the phone). From that moment on, the product does not check the license key at startup, but the activation data, which needs the computer to be the same in order to validate (otherwise, the DATA would be different and the digital signature would not validate). Note that the activation data checking do not require verification over the Internet: it is sufficient to verify the digital signature of the activation data with the public key already embedded in the product.
Well, just eliminate redundant characters like '1', 'l', '0', 'o' from your keys. Split the license key string into groups of characters.
Simple answer - No matter what scheme you use it can be cracked.
Don't punish honest customers with a system meant to prevent hackers, as hackers will crack it regardless.
A simple hashed code tied to their email or similar is probably good enough. Hardware based IDs always become an issue when people need to reinstall or update hardware.
Good thread on the issue:http://discuss.joelonsoftware.com/default.asp?biz.5.82298.34
palerdotWhen generating the key, don't forget to concatenate the version and build number to the string you calculate the hash on. That way there won't be a single key that unlocks all everything you ever released.
After you find some keys or patches floating in astalavista.box.sk you'll know that you succeeded in making something popular enough that somebody bothered to crack. Rejoice!
shooshshooshBesides what has already been stated..
Any use of .NET applications are inherently breakable because of the intermediate language issues. A simple disassembly of the .NET code will open your product to anyone. They can easily bypass your licensing code at that point.
You can't even use hardware values to create a key anymore. Virtual machines now allow someone to create an image of a 'licensed' machine and run it on any platform they choose.
If it's expensive software there are other solutions. If it's not, just make it difficult enough for the casual hacker. And accept the fact that there will be unlicensed copies out there eventually.
If your product is complicated, the inherent support issues will be create some protection for you.
The C# / .NET engine we use for licence key generation is now maintained as open source:
https://github.com/appsoftware/.NET-Licence-Key-Generator.
It's based on a 'Partial Key Verification' system which means only a subset of the key that you use to generate the key has to be compiled into your distributable. You create the keys your self, so the licence implementation is unique to your software.
As stated above, if your code can be decompiled, it's relatively easy to circumvent most licencing systems.
gb2dgb2dI've used Crypkey in the past. It's one of many available.
You can only protect software up to a point with any licensing scheme.
Mitch WheatMitch WheatI don't know how elaborate you want to get
but i believe that .net can access the hard drive serial number.
you could have the program send you that and something eles ( like user name and mac address of the nic)
you compute a code based off that and email them back the key.
they will keep them from switching machines after they have the key.
Crash893Crash893I'm one of the developers behind the Cryptolens software licensing platform and have been working on licensing systems since the age of 14. In this answer, I have included some tips based on experience acquired over the years.
The best way of solving this is by setting up a license key server that each instance of the application will call in order to verify a license key.
Benefits of a license key server
The advantages with a license key server is that:
- you can always update or block a license key with immediate effect.
- each license key can be locked to certain number of machines (this helps to prevent users from publishing the license key online for others to use).
Considerations
Although verifying licenses online gives you more control over each instance of the application, internet connection is not always present (especially if you target larger enterprises), so we need another way of performing the license key verification.
The solution is to always sign the license key response from the server using a public-key cryptosystem such as RSA or ECC (possibly better if you plan to run on embedded systems). Your application should only have the public key to verify the license key response.
So in case there's no internet connection, you can use the previous license key response instead. Make sure to store both the date and the machine identifier in the response and check that it's not too old (eg. you allow users to be offline at most 30 days, etc) and that the license key response belongs to the correct device.
Note you should always check the certificate of license key response, even if you are connected to the internet), in order to ensure that it has not been changed since it left the server (this still has to be done even if your API to the license key server uses https)
Protecting secret algorithms
Most .NET applications can be reverse engineered quite easily (there is both a diassembler provided by Microsoft to get the IL code and some commercial products can even retrieve the source code in eg. C#). Of course, you can always obfuscate the code, but it's never 100% secure.
I most cases, the purpose of any software licensing solution is to help honest people being honest (i.e. that honest users who are willing to pay don't forget to pay after a trial expires, etc). Microsoft office 2010 25 serial key.
However, you may still have some code that you by no means want to leak out to the public (eg. an algorithm to predict stock prices, etc). In this case, the only way to go is to create an API endpoint that your application will call each time the method should be executed. It requires internet connection but it ensures that your secret code is never executed by the client machine.
Implementation
If you don't want to implement everything yourself, I would recommend to take a look at this tutorial (part of Cryptolens)
The only way to do everything you asked for is to require an internet access and verification with a server. The application needs to sign in to the server with the key, and then you need to store the session details, like the IP address. This will prevent the key from being used on several different machines. This is usually not very popular with the users of the application, and unless this is a very expensive and complicated application it's not worth it.
You could just have a license key for the application, and then check client side if the key is good, but it is easy to distribute this key to other users, and with a decompiler new keys can be generated.
MariusMariusI've implemented internet-based one-time activation on my company's software (C# .net) that requires a license key that refers to a license stored in the server's database. The software hits the server with the key and is given license information that is then encrypted locally using an RSA key generated from some variables (a combination of CPUID and other stuff that won't change often) on the client computer and then stores it in the registry.
It requires some server-side coding, but it has worked really well for us and I was able to use the same system when we expanded to browser-based software. It also gives your sales people great info about who, where and when the software is being used. Any licensing system that is only handled locally is fully vulnerable to exploitation, especially with reflection in .NET. But, like everyone else has said, no system is wholly secure.
In my opinion, if you aren't using web-based licensing, there's no real point to protecting the software at all. With the headache that DRM can cause, it's not fair to the users who have actually paid for it to suffer.
I strongly believe, that only public key cryptography based licensing system is the right approach here, because you don't have to include essential information required for license generation into your sourcecode.
In the past, I've used Treek's Licensing Library many times, because it fullfills this requirements and offers really good price. It uses the same license protection for end users and itself and noone cracked that until now. You can also find good tips on the website to avoid piracy and cracking.
Like a few others mentioned, I'm a huge opponent of being hostile to customers by default—something that the licensing industry is notorious for. So I'll expand on a good solution for your problem that also offers a good customer UX.
To start off, you mentioned that you have a 'limited' version of your software that you're using to try and convert customers to 'upgrade' for additional features. So what you're looking for are feature licenses for your product e.g. a customer can purchase a license for feature-X or feature-Y.
I built Keygen with this type of licensing in mind. Keygen is a licensing REST API that allows you to manage user accounts, licenses and also track machine usage/associations.
What I would do is set up 2 license types (a policy within Keygen) where one is a base policy for the limited free version, and the other is a policy for the paid version.
I'm not sure what you're using for payments, but let's assume you're using something like Stripe (pretty standard nowadays) that offers webhooks. Keygen also has webhooks (whether you use it or not, all this is still applicable). You can integrate Keygen to talk with your payment provider using webhooks from both sides (think: customer.created->create base license for customer, license.created->charge customer for the new license).
So by utilizing webhooks, we can automate license creation for new customers. So what about license validation within the application itself? This can be done in a variety of ways, but the most popular way is by requiring your customer to enter a long license key into an input field which you can then validate; I think this is a terrible way to handle license validation in your application.
Why do I think that? Well first off, you're requiring your customer to input a tediously long license key that is meant for machine consumption, and second your requiring you and your customer to keep track of said tediously long license key.
Okay, so what's an alternative? I think the best alternative is doing something all of your customers are used to: allowing them to create an account for your product using an email/password. You can then associate all of their licenses and their machines with that account. So now instead of inputting a license key, they can simply log in using their credentials.
What advantage does that give you? Firstly, it gets rid of the need for you and your customers to keep track of license keys, since it's all handled behind-the-scenes inside of their user account and most importantly: you can now offer your customers self-serve license and machine activation! i.e. since all of their licenses and machines are associated with their user account, you can prompt them to purchase a license when they fire up your application on an unrecognized machine.
Now onto license validation: whenever your customer logs into your application with their email/password, you can query their user account for the licenses they own to determine if they can use feature-X or feature-Y. And since your application is now self-serve, you can allow your customers to purchase additional features directly from within your application!
So we've introduced a ton of automation to our licensing system, we can license individual features (i.e. a limited vs. full version), we've offered an awesome UX for our customers and we've also alleviated one of the biggest reasons for support requests: license key recovery.
Anyways, this got long but hopefully it helps somebody!
It is not possible to prevent software piracy completely. You can prevent casual piracy and that's what all licensing solutions out their do.
Node (machine) locked licensing is best if you want to prevent reuse of license keys. I have been using Cryptlex for about a year now for my software. It has a free plan also, so if you don't expect too many customers you can use it for free.
adnan kamiliadnan kamiliYou can use a free third party solution to handle this for you such as Quantum-Key.Net It's free and handles payments via paypal through a web sales page it creates for you, key issuing via email and locks key use to a specific computer to prevent piracy.
Your should also take care to obfuscate/encrypt your code or it can easily be reverse engineered using software such as De4dot and .NetReflector. A good free code obfuscator is ConfuserEx wich is fast and simple to use and more effective than expensive alternatives.
You should run your finished software through De4Dot and .NetReflector to reverse-engineer it and see what a cracker would see if they did the same thing and to make sure you have not left any important code exposed or undisguised.
Your software will still be crackable but for the casual cracker it may well be enough to put them off and these simple steps will also prevent your code being extracted and re-used.
License Key Generator In C#.net
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I'm implementing a small application in C, which I would like to sell as shareware for a reasonable price later on. It will start of with a 30-day trial, which I am already quite certain of how to implement it.
The problem I have, though, is that I am not quite sure how to implement the product key verification. What I have in mind is that the customer can sign up on my webpage (after trying the product for a while), pay for the product, and get a product key in the form of aaaaa-bbbbb-ccccc-ddddd-eeeee via e-mail (or maybe available via his profile on my website). No problem so far. He/She then drops the key in the appropriate key fields in my app and boom the app is registered.
From what I could gather so far, people either recommend AES or RSA for this. To be honest, I in another direction in college (not cryptography) and the one cryptography class I took was some time ago. But from what I remember, AES is a symmetric encryption algorithm, which would mean that I would only have one key for encryption and decryption, right? How could I then generate thousands of product keys and still validate them in my app (which by the way won't require internet access..so no checking back with a server)?
So I guess RSA would be the way to go? But doesn't RSA produce pretty long keys (at least longer than the required 25 characters from above)?
In another thread I read that some products won't even use encryption for the product key generation/verification, but instead just employ some checks like 'add the 2. and the 17. character and that should total to x'.
What's the fastest, easiest and most secure way to go here? :-) Code samples would be sugar!
https://quaevendeghyd.tistory.com/1. Regards,
Sebastian
P.S.: Oh..and please don't tell me how my key can and will be cracked at some point...I know about that, which is primarily why I don't want to spend a lot of time with this issue, but at the same time not make it too easy for the occasional cracker.
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5 Answers
Symmetric algorithms are limited, in that any novice cracker with a disassembler can find your key (or the algorithm used to generate one) and make a 'keygen'.
For this reason, asymmetric cryptology is the way to go. The basic premise is something like this:
- When the user purchases a license from you, you collect certain identifying details about the user and/or their environment (typically, this is just a full name; sometimes a company, too).
- You make a 128-bit MD5 hash of this information.
- Using a 128-bit Elliptic Curve crypto, encrypt this hash using the private key on the server.
- The 128-bit cipher text can be represented to the user as a 25-character string consisting of letters and digits (plus separating dashes for readability). Notice that 26 letters + 10 digits = 36 discrete values, and that 36^25 > 2^128.
- The user types this product key into your registration dialog. The client software converts it back to a 128-bit number (16 bytes), decrypts that using the public key of your EC crypto, and compares the result to an MD5 hash of the user's personal information, which must match what was used for registration.
This is just the basic idea, of course. For more details and source code, see Product Keys Based on Elliptic Curve Cryptography.
C8H10N4O2Life is simpler if you simply purchase a solution.
https://quaevendeghyd.tistory.com/2. Kagi allows you to collect payments and they help you manage the keys.
S.LottS.LottA guy has blogged about how he handled the question of registration numbers. One of his blog entries is Generating Unique Registration Numbers.
mouvicielmouvicielYes, RSA and AES are two very different things:
- RSA is public key cryptography, involving a public key and a private key, and is fairly slow. The primary use is to set up a secure exchange of a symmetric encryption session key.
- AES is symmetric encryption, which is fast and secure.
License Key Generator In C#
Since your app does not communicate over public channels and the use of cryptography is limited to product activation/registration you'll want to go with a symmetric cipher. The benefits of public key ciphers is in key management, which you will be handling on your web site or through email.
Note that you do not have to distribute the same key for every customer. You could generate a hash of some of the registration info and XOR it with something else (a fixed session key, perhaps). Send that to the customer, and the program could generate the same hash and XOR will the key you sent to produce the original fixed key.
Dealing with cryptography is not something to be done lightly. As you mention, you expect this to be cracked. If you're doing your own this will almost certainly happen. You can still use your own implementation to 'keep honest people honest,' but realize that's as far as you'll get. If you need something stronger then you should purchase a solution after doing thorough research on the solutions.
dwcdwcYou can check out this Code Project article. It describes an implementation of a a software key based on the MAC address of the machine where the software is executed. The method is not ideal, as the auteur himself admits, and it is a little bit different from what you are looking for, but maybe it can help you.
Serial Key
Dani van der MeerDani van der MeerNot the answer you're looking for? Browse other questions tagged cencryptionlicensingkeyproduct or ask your own question.