Protection PLUS 4 SDK versus Protection PLUS 5 SDK

The previous generation, Protection PLUS 4 SDK, has been the licensing system of choice for thousands of software developers for well over 15 years. The initial design of Protection PLUS 5 SDK started in 2009 with the release of the PLUSManaged library for .NET, in use by many new and existing Protection PLUS 4 SDK customers. Although Protection PLUS 5 SDK has been well received even by existing Protection PLUS 4 SDK customers, migrating from Protection PLUS 4 SDK to Protection PLUS 5 SDK is not seamless. Protection PLUS 5 SDK is an entirely new product built from the ground up from much of the same technologies and experiences that made Protection PLUS 4 SDK powerful.

When we first set out to create Protection PLUS 5 SDK APIs, we had the following design goals in mind:

Leverage all of the knowledge learned since Protection PLUS 4 SDK was released, based upon feedback from customers
Simplify the set of API interfaces available, and make the APIs easier to use and understand
Combine the Automation Client (SKCAxx.dll), SWKClientServices, and Licensing Client (KEYLIBxx.dll) into a single library
Make it easy to call SOLO Server web services from a standard API
Use XML for the License File format for the greatest extensibility
Use the RSA Algorithm to leverage public key cryptography and digital signatures to better secure the license file and its data
Full support for UNICODE character sets
Support additional platforms (such as macOS and Linux) and processor architectures
Create the .NET component in 100% managed code to provide the greatest .NET project compatibility
Create a secure activation process that eliminates the 14-bit limitation on user-defined data
Provide the same features and increased security across all activation methods – online, email, activation from another computer that has Internet access
Introduce new methods of licensing and activating, such as volume licenses, and downloadable licenses with activation

Comparison of Technology and Features

Feature	Protection PLUS 4 SDK	Protection PLUS 5 SDK
License File	Fixed-size, proprietary format, which cannot not always accommodate highly customized information.	Variable-size, XML format, easily accommodates highly customized information.
Cryptographic Strength	Proprietary, symmetric encryption algorithm.	Uses the RSA Algorithm for strong, scalable, asymmetric (public key) cryptography and digital signatures.
Activation	Based off an exchange of 32-bit numeric values (called Trigger Codes), can only accommodate a very limited license parameters, often called Payload.	Based off an exchange of encrypted and digitally signed XML blobs, and can accommodate a much larger payload. Also includes high-level support for processing Protection PLUS 4 SDK activation codes (Trigger Codes).
System Identification	Uses up to 17 fixed pieces of information to authorize and verify licensed computers locally. Only a very small subset of this information is used during activation, however.	Includes a variety of algorithms designed to use any combination of data to authorize and verify licensed computers. Also supports defining your own algorithms, which enables you to use your own, customized sources of information for system identification. Additionally, the XML-formatted data is used during activation, which makes it much easier to tell what pieces of information changed, if needed. Although the number of algorithms available in Protection PLUS 5 SDK is limited (because of the extra effort required to support multiple platforms), this will be expanded over time.
Copy Protection	A fixed vote-weight system is used to detect changes made to a computer after activation. The amount of change allowed before a license is revoked is controlled by a numeric threshold value.	Discrete algorithms give you full control over which algorithms are used, and how many algorithms must match after activation.
SOLO Server Integration APIs	Includes the separate APIs, Automation Client (for native applications) and SWKClientServices (for .NET applications) for SOLO Server integration.	Everything you need for SOLO Server integration is now built-in with whichever Protection PLUS 5 SDK API you use.
Native API Operating System Support	Supports running 32-bit applications on 32-bit and 64-bit versions of Windows, and running 64-bit applications on 64-bit versions of Windows.	Supports Windows and other POSIX-compliant operating systems (such as macOS and most popular and current Linux distributions).
.NET APIs	Includes a 32-bit (only supports 32-bit applications, though 64-bit versions of Windows are supported), mixed-mode library named SKCLNET. This has some limitations as to where it can be used (due to limitations in the .NET framework with using strong named, mixed-mode assemblies).	Fully managed, .NET class library named PLUSManaged, which is architecture independent (targets "Any CPU"), and supports 32-bit and 64-bit operating systems and applications.
ActiveX/COM APIs	Includes a 32-bit (only supports 32-bit applications, though 64-bit versions of Windows are supported) ActiveX component named SKCL.	No ActiveX/COM library is presently available for Protection PLUS 5 SDK.
License File I/O	Every time a license file field is read, the entire license file is read from the file system. Every time a license file field is written, the entire license file is read from the file system, the field is updated, and then the entire license file is written. This approach makes it easier to avoid synchronization issues in high-concurrency environments, but can also reduce performance (especially when the license file is stored in a shared folder on a network).	The license file is only read and loaded in to memory, and is only written to the file system, when your application makes explicit API calls to do so. This improves performance in lower-concurrency environments, but also means you need to be mindful of this behavior and the possibility of synchronization issues in high-concurrency environments. A major reason why this approach was taken is to minimize the amount of cryptography done when working with license file data, which especially important to minimize in high-concurrency/server environments.
Network Floating Licensing	Supported through the use of semaphore files hosted on a Windows shared folder on a network.	.NET applications using PLUSManaged support Network Floating Licensing through the use of semaphore files hosted on a Windows shared folder on a network. PLUSManaged
Cloud-Controlled Network Floating Licensing using SOLO Server	Not supported.	These web services may also be used to automate authorization of "check-outs" for temporary, off-line use of the licensed application. If you would like to use this functionality or see it demonstrated, contact us. These features are not yet available, but are planned for, native applications using PLUSNative.
Simplified APIs	Protection PLUS 4 SDK includes EZTrial1, which simplifies licensing and trial-ware implementations; and EZTrial2, which is like EZTrial1 with a pre-defined GUI. EZTrial was replaced with the Instant Protection PLUS 3 licensing wizard.	Although there are no simplified APIs similar to EZTrial, Protection PLUS 5 SDK includes sample source code which is highly configurable, and makes it easy for you to adopt licensing and trial-ware functionality in your application, while also giving you the highest level of flexibility and control. Additionally, a pre-defined GUI is available for .NET applications via the PLUSManagedGui library.
License File Editor	LFEdit can be used to view, edit, and create Protection PLUS 4 SDK license files. An additional utility (LFRW.exe) is included to view or edit some internal fields that are not visible in LFEdit. These applications only run in Windows.	Most customers use SOLO Server to create Protection PLUS 5 SDK license files, as part of an automated activation process. Alternatively, License Manager allows you to view, edit, and create both read-only and writable license files regardless of whether or not you are using SOLO Server. License Manager runs in Windows, macOS, and most popular Linux distributions. (See system requirements for details.)

Additional differences worth noting include:

Protection PLUS 4 SDK was introduced in 1997, while Protection PLUS 5 SDK was first released in 2009 with the PLUSManaged API. PLUSNative was added to the Protection PLUS 5 SDK toolkit in 2012.
The Protection PLUS 5 SDK APIs are still evolving over time. There is not a 100% feature match between the Protection PLUS 4 SDK and Protection PLUS 5 SDK, especially with the PLUSNative library.
There is not currently a way to read a Protection PLUS 4 SDK license file with the Protection PLUS 5 SDK libraries. We feel that in most cases, customers will want to switch to Protection PLUS 5 SDK in a major release of their software where product re-activation would likely occur. However, it is possible to automate the upgrade from Protection PLUS 4 SDK to Protection PLUS 5 SDK for your customers licenses.