When I originally wrote this answer it was under an assumption that the question was regarding 'offline' validation of licence keys. Check tis article on which covers the following requirements:.License keys must be easy enough to type in.We must be able to blacklist (revoke) a license key in the case of chargebacks or purchases with stolen credit cards.No “phoning home” to test keys.
Although this practice is becoming more and more prevalent, I still do not appreciate it as a user, so will not ask my users to put up with it.It should not be possible for a cracker to disassemble our released application and produce a working “keygen” from it. This means that our application will not fully test a key for verification. Only some of the key is to be tested.
Further, each release of the application should test a different portion of the key, so that a phony key based on an earlier release will not work on a later release of our software.Important: it should not be possible for a legitimate user to accidentally type in an invalid key that will appear to work but fail on a future version due to a typographical error. I've not got any experience with what people actually do to generate CD keys, but (assuming you're not wanting to go down the road of online activation) here are a few ways one could make a key:.Require that the number be divisible by (say) 17.
Trivial to guess, if you have access to many keys, but the majority of potential strings will be invalid. Similar would be requiring that the checksum of the key match a known value.Require that the first half of the key, when concatenated with a known value, hashes down to the second half of the key.
Better, but the program still contains all the information needed to generate keys as well as to validate them.Generate keys by encrypting (with a private key) a known value + nonce. This can be verified by decrypting using the corresponding public key and verifying the known value. The program now has enough information to verify the key without being able to generate keys.These are still all open to attack: the program is still there and can be patched to bypass the check. Cleverer might be to encrypt part of the program using the known value from my third method, rather than storing the value in the program. That way you'd have to find a copy of the key before you could decrypt the program, but it's still vulnerable to being copied once decrypted and to having one person take their legit copy and use it to enable everyone else to access the software. CD-Keys aren't much of a security for any non-networked stuff, so technically they don't need to be securely generated.
If you're on.net, you can almost go with Guid.NewGuid.Their main use nowadays is for the Multiplayer component, where a server can verify the CD Key. For that, it's unimportant how securely it was generated as it boils down to 'Lookup whatever is passed in and check if someone else is already using it'.That being said, you may want to use an algorhithm to achieve two goals:.
Have a checksum of some sort. That allows your Installer to display 'Key doesn't seem valid' message, solely to detect typos (Adding such a check in the installer actually means that writing a Key Generator is trivial as the hacker has all the code he needs. Not having the check and solely relying on server-side validation disables that check, at the risk of annoying your legal customers who don't understand why the server doesn't accept their CD Key as they aren't aware of the typo). Work with a limited subset of characters.
Trying to type in a CD Key and guessing 'Is this an 8 or a B? A Q or an O or a 0?' - by using a subset of non-ambigous chars/digits you eliminate that confusion.That being said, you still want a large distribution and some randomness to avoid a pirate simply guessing a valid key (that's valid in your database but still in a box on a store shelf) and screwing over a legitimate customer who happens to buy that box. If you aren't particularly concerned with the length of the key, a pretty tried and true method is the use of public and private key encryption.Essentially have some kind of nonce and a fixed signature.For example:0089Where 0001 is your nonce and 123456789 is your fixed signature.Then encrypt this using your private key to get your CD key which is something like:ABCDEFThen distribute the public key with your application. The public key can be used to decrypt the CD key 'ABCDEF', which you then verify the fixed signature portion of.This then prevents someone from guessing what the CD key is for the nonce 0002 because they don't have the private key.The only major down side is that your CD keys will be quite long when using private / public keys 1024-bit in size.
You also need to choose a nonce long enough so you aren't encrypting a trivial amount of information.The up side is that this method will work without 'activation' and you can use things like an email address or licensee name as the nonce. The key system must have several properties:. very few keys must be valid. valid keys must not be derivable even given everything the user has. a valid key on one system is not a valid key on another.
othersOne solution that should give you these would be to use a. Start with a 'system hash' (say grab the macs on any NICs, sorted, and the CPU-ID info, plus some other stuff, concatenate it all together and take an MD5 of the result (you really don't want to be handling if you don't have to)) append the CD's serial number and refuse to boot unless some registry key (or some datafile) has a valid signature for the blob.
The user activates the program by shipping the blob to you and you ship back the signature.Potential issues include that you are offering to sign practically anything so you need to assume someone will run a and/or attacks. That can be mitigated by checking the serial number provided and refusing to handle request from invalid ones as well as refusing to handle more than a given number of queries from a given s/n in an interval (say 2 per year)I should point out a few things: First, a skilled and determined attacker will be able to bypass any and all security in the parts that they have unrestricted access to ( i.e. Everything on the CD), the best you can do on that account is make it harder to get illegitimate access than it is to get legitimate access. Second, I'm no expert so there could be serious flaws in this proposed scheme. There are also DRM behaviors that incorporate multiple steps to the process. One of the most well known examples is one of Adobe's methods for verifying an installation of their Creative Suite.
The traditional CD Key method discussed here is used, then Adobe's support line is called. The CD key is given to the Adobe representative and they give back an activation number to be used by the user.However, despite being broken up into steps, this falls prey to the same methods of cracking used for the normal process. The process used to create an activation key that is checked against the original CD key was quickly discovered, and generators that incorporate both of the keys were made.However, this method still exists as a way for users with no internet connection to verify the product. Going forward, it's easy to see how these methods would be eliminated as internet access becomes ubiquitous.
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.SQL Server Compact 3.5 SP2 includes a host of new features including the following:. Support for the Transact-SQL Editor in Visual Studio 2010 that can be used to run free-text T-SQL queries and to view query show-plans for optimizing queries. Exposes the Change Tracking feature as an application programming interface (API), namely, System.Data.SqlServerCe.SqlCeChangeTracking. Supported Operating SystemWindows 7, Windows Server 2003 R2 (32-Bit x86), Windows Server 2003 R2 x64 editions, Windows Server 2003 Service Pack 2, Windows Server 2003 Service Pack 2 x64 Edition, Windows Server 2008 R2, Windows Server 2008 Service Pack 2, Windows Vista Service Pack 2, Windows XP Service Pack 3. For the Windows mobile platform, see the download page.Development Computer:. 2 to 3 MB of available hard disk space.
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An additional 2 to 3 MB of space must be also available for temporary setup files. Visual Studio 2010 and Visual Studio 2008 SP1 for Visual Studio designer support for developing application for Windows desktop. For developing applications for Windows mobile devices use Visual Studio 2008 SP1. Visual Studio 2005 SP1 supported for code based scenarios for Windows desktop and mobile devices.NET Framework 2.0, 3.0, 3.5 or 4 for managed application development.The file available for download is a self-extracting executable (exe) file that contains the 32-bit and the 64-bit Windows Installer (MSI) files for installing SQL Server Compact 3.5 SP2 on a 32-bit and a 64-bit Computer. The exe file needs 6 MB of available hard disk space for extracting the MSIs.To download the SQL Server Compact 3.5 SP2 (SSCERuntime-ENU.exe):. In the Files in this Download section at the bottom of this page, click the SSCERuntime-ENU.exe link. Do one of the following:.
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To start the extraction immediately, click Open or Run this program from its current location and specify an extraction location on your computer. To copy the download to your computer for extraction at a later time, click Save or Save this program to disk and specify a location to save the.exe file on your computer. SQL Server Compact 3.5 SP2 is freely redistributable under a redistribution license agreement. Application developers redistributing SQL Server Compact 3.5 SP2 can optionally register at the.
Registering will help the developers in getting information about SQL Server Compact critical security patches and hot fixes that can be further applied to the client installations. The existing installations of SQL Server Compact 3.5 or SQL Server Compact 3.5 SP1 on the Computer are upgraded to the released version of SQL Server Compact 3.5 SP2 by installing SQL Server Compact 3.5 SP2 using the MSI file. Other downloads for SQL Server Compact 3.5 SP2 are listed below:.