密钥系统必须具有以下几个属性:

只有很少的键是有效的 即使给定用户拥有的一切，有效的键也必须是不可派生的。 一个系统上的有效密钥在另一个系统上不是有效密钥。 其他人

One solution that should give you these would be to use a public key signing scheme. 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 personally identifiable information 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.

潜在的问题包括，你提供的签名几乎是任何东西，所以你需要假设有人会运行选定的纯文本和/或选定的密文攻击。可以通过检查提供的序列号并拒绝处理来自无效序列号的请求，以及拒绝在一段时间内(例如每年2次)处理来自给定s/n的超过给定数量的查询来缓解这一问题。

我应该指出几件事:首先，一个熟练和坚定的攻击者将能够绕过他们拥有无限制访问权限的部分(即CD上的所有内容)的任何和所有安全性，您对该帐户所能做的最好的事情是使其更难获得非法访问而不是获得合法访问。其次，我不是专家，所以这个提议的方案可能存在严重的缺陷。

所有的CD拷贝保护算法给诚实的用户带来不便，同时没有提供任何防止盗版的保护。

“盗版者”只需要获得一张合法的cd及其访问代码，他就可以制作n份拷贝并分发它们。

无论代码的加密安全性如何，都需要以明文形式提供CD，否则合法用户无法激活该软件。

Most secure schemes involve either the user providing the software supplier with some details of the machine which will run the software (cpu serial numbers, mac addresses, Ip address etc.), or, require online access to register the software on the suppliers website and in return receive an activitation token. The first option requires a lot of manual administration and is only worth it for very high value software, the, second option can be spoofed and is absolutly infuriating if you have limited network access or you are stuck behind a firewall.

总的来说，与客户建立信任关系要容易得多!

我对人们如何生成CD密钥没有任何经验，但是(假设你不想走在线激活的道路)这里有一些方法可以生成密钥:

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.

这些漏洞仍然容易受到攻击:程序仍然存在，可以通过打补丁绕过检查。更聪明的方法可能是使用第三个方法的已知值加密部分程序，而不是将值存储在程序中。这样，在解密程序之前，你必须找到密钥的副本，但一旦解密，它仍然很容易被复制，并且有一个人拿着他们的合法副本，并使用它使其他人能够访问软件。

cd - key对于任何非网络的东西都不是很安全，所以从技术上讲，它们不需要安全生成。如果你使用的是。net，你几乎可以使用guide . newguid()。

它们现在主要用于多人游戏组件，服务器可以在其中验证CD Key。因此，生成它的安全性并不重要，因为归根结底就是“查找传入的任何东西，并检查其他人是否已经在使用它”。

话虽如此，你可能想要使用算法来实现两个目标:

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 1 or an I? a Q or an O or a 0?" - by using a subset of non-ambigous chars/digits you eliminate that confusion.

话虽如此，你仍然需要一个大的分布和一些随机性，以避免盗版只是猜测一个有效的密钥(在你的数据库中是有效的，但仍然在商店货架上的一个盒子里)，并欺骗碰巧买了那个盒子的合法客户。

您可以在使用它的软件项目中非常容易地使用和实现安全许可API(您需要从https://www.systemsoulsoftwares.com/下载创建安全许可的桌面应用程序)。

Creates unique UID for client software based on System Hardware(CPU,Motherboard,Hard-drive) (UID acts as Private Key for that unique system) Allows to send Encrypted license string very easily to client system, It verifies license string and works on only that particular system This method allows software developers or company to store more information about software/developer/distributor services/features/client It gives control for locking and unlocked the client software features, saving time of developers for making more version for same software with changing features It take cares about trial version too for any number of days It secures the License timeline by Checking DateTime online during registration It unlocks all hardware information to developers It has all pre-build and custom function that developer can access at every process of licensing for making more complex secure code

如果您不是特别关心密钥的长度，那么使用公钥和私钥加密是一种行之有效的方法。

本质上有某种临时的和固定的签名。

例如: 0001 - 123456789

其中0001是您的临时签名，123456789是您的固定签名。

然后用你的私钥加密，得到你的CD密钥，就像这样: ABCDEF9876543210

然后在应用程序中分发公钥。公钥可用于解密CD密钥“ABCDEF9876543210”，然后验证其固定签名部分。

这可以防止某人猜测nonce 0002的CD密钥是什么，因为他们没有私钥。

唯一的主要缺点是，当使用1024位的私有/公共密钥时，您的CD密钥将非常长。您还需要选择一个足够长的nonce，这样您就不会加密少量的信息。

好的一面是，这种方法不需要“激活”就可以工作，你可以使用电子邮件地址或被许可方的名称作为临时标识。