Generating and verifying license keys is a common requirement for a lot commercial softwarethese days. From desktop applications such as those built on frameworks like Electronor Qt, to dual-licensed open source packages and libraries like Sidekiq,to a variety of other on-premise software applications and dependencies.
Sketch 3 License Key Crack
When it comes to software licensing, the key generation and verification algorithms vendorschoose can make or break a licensing system. After an algorithm has been compromised, a vendorcan no longer trust any previously generated license keys, including those belonging to legitend-users.
Both of these solutions can come at a huge cost, both in terms of end-user trust, support costs,as well as engineering resources. Suffice it to say, it's a bad situation. And ideally, what wewant to do is avoid the situation entirely, by choosing a modern, secure license keyalgorithm from the get-go.
Software "cracking" is the act of directly modifying the source code of a software applicationto bypass its licensing system entirely. As much as vendors hate to hear it: all applicationsinstalled on an end-users device are susceptible to cracking.
Software cracks usually only work for a single version of a particular application, sincethe application code itself is modified to bypass any license checks (meaning a softwareupdate often requires an updated crack for the new application code.) Distributing acracked version of an application falls on the bad actor.
The other major attack vector is known as a software "keygen", which is much more ominous. Asits name may imply, a keygen is a form of software, often a separate program or webpage, thatgenerates valid license keys, i.e. a key-generator, or "keygen."
Most software vendors have some type of license keygen, which they keep secret. For example, aftera user submits a successful purchase order, part of the order process calls a key generator, whichgenerates a valid, legitimate license key for the new customer.
Depending on your key generation algorithm, a keygen like this may only be able to generate validkey for a single version of an application. But in the worst case, a bad actor can create a keygenthat generates valid license keys that work across all versions of an application, requiringa complete upheaval of the product's licensing system.
It's also worth mentioning that keygens are much more valuable to bad actors than cracks, becausea keygen can be used on the real application, vs the bad actor having to distribute a modified,cracked version of the application.
Partial Key Verificationis a software license key algorithm that partitions a product key into multiple "subkeys."With each new version of your product, your license key verification algorithm will check a differentsubset of a license's subkeys.
Our PKV keygen should be a tightly kept trade secret, because with it comes the power to craftlicense keys at-will. But we'll soon realize, much to our demise, keeping a PKV keygen secretis actually not possible.
If you notice, getSubkeyFromSeed(seed, 24, 3, 200) is deriving an expected 0th subkey from theseed value. We then compare the expected 0th subkey to our license key's actual 0th subkey. If thesubkeys don't match, the license key is not valid.
Some applications will have a central point in the bytecode where this check happens, but othersharden their system by inlining the license key checks, making the work of a bad actor wanting tocrack the software much, much harder. But licensing is all essentially the same: it's a seriesof conditionals.
When choosing a modern license key algorithm, we have a quite a few solid options. For example, ourAPI supports a variety of cryptographic schemes for license keys, from elliptic-curve signatures,to RSA signatures and even encryption. Today, we'll be covering elliptic-curve and RSA-2048 signatures.
The license keys we generate may differ in length, depending on the cryptographic scheme we use,but the format is going to stay the same: some encoded data, a delimiter ".", and a cryptographicsignature of the data. (This is more or less the same format our API uses for cryptographic keys.)
After generating our keypair, we're going to want to keep those encoded keys in a safeplace. We'll use the private signing key for our keygen, and we'll use the publicverify key to verify authenticity of license keys within our application.
What's great about this license key format is that we can embed any dataset intoit that we need. Right now, we're embedding the customer's email, but we could includeother information as well, such as order ID, key expiration date, entitlements, andmore. (It could even be a JSON object, which is actually the default for our API.)
One downside is that the more data you embed, the larger the license keys will become.But in the real world, this isn't really an issue, since the majority of users willcopy-and-paste their license keys, as opposed to typing them in by hand.
And as expected, like our keypair, our license keys are also much larger. But they'resecure. And remember, most users copy-and-paste, so length doesn't really matter.(You could even wrap license keys in a license.dat file, which makes distributiona breeze. But that's just an implementation detail.)
Once again, it takes less than 10 lines of code to verify license keys withinyour application. Our RSA implementation can be improved by using a more modernnon-deterministic padding scheme, PKCS1-PSS (which our API also supports.)
But remember, a crack != a keygen, so your application's licensing always runsthe risk of being circumvented via code modification. But license keys cannotbe forged when you utilize a licensing system built on modern cryptography.
Generating and verifying the authenticity of cryptographically signed license keyslike we've covered will work great for a lot of licensing needs. The implementationis straight forward, it's secure, and these types of license keys work especiallygreat for offline-first perpetual licenses (or a timed license with an embedded,immutable expiry).
You get your license for the application right after purchase of CleanMyMac 3 - we send your unique activation number in an email. Click it to activate CleanMyMac 3, or copy and paste the number into the activation window of the app.
If you specified correct information, you'll see a list of all MacPaw product licenses you've purchased earlier. Simply click on the "Send to email" link next to the appropriate product to resend the activation code to your email. In case the license retrieval wasn't successful, please send an email to our Support Team, and we'll do our best to help you.
Go to macpaw.com/store and buy a CleanMyMac 3 license. You can either get a single license or a license for 2 or 5 Macs. In any case, you will receive an email with your CleanMyMac 3 activation key immediately after the purchase.
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