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Protect Models to Conceal Contents

When you want to share a model with a third party without revealing intellectual property, protect the model. Protecting a model conceals the implementation details of the original model by compiling it into a referenced model. The protected model includes derived files to support the optional functionalities that you specify.

When you protect a model, you can allow the user of the protected model to:

  • Simulate a model that includes the protected model in normal, accelerator, or rapid accelerator mode.

  • Open a read-only web view of the model, including model contents and block parameters. Creating a read-only web view of the model requires Simulink® Report Generator™.

  • Generate code for a model that includes the protected model.

  • Generate HDL code for a model that includes the protected model.

  • Generate code for the protected model through the standalone interface, if you have Embedded Coder® and specify an ERT-based system target file for the model.

You can optionally password-protect each option. If you choose-password protection for one of these options, the software protects the supporting files by using AES-256 encryption.

When you create a protected model:

  • Simulink creates and stores a protected version of the model in a file that has the same name as the source model, with an .slxp extension.

  • The original model file, with the .slx extension, does not change. If you protect the model through a Model block, that Model block does not change.

  • Optionally, Simulink creates a project archive (.mlproj) that contains the protected model, a harness model for the protected model, and additional supporting files.

This example shows how to create a protected model from a referenced model for read-only viewing, simulation, or code generation.

Prepare the Parent Model

Configure the Model blocks in the parent model to refer to the original referenced model. This step prevents the Model blocks from becoming protected references when you create the protected model.

  1. Open the parent model that references the model you want to protect. For this example, open the model sldemo_mdlref_basic.

  2. To run the workflow, create a local copy of the model sldemo_mdlref_counter that you want to protect. You can then create a local copy of the parent model sldemo_mdlref_basic. You must save the parent model in the same folder as the referenced model.

  3. Open the sldemo_mdlref_basic model that you saved locally. Make sure that the Model blocks CounterA, CounterB, and CounterC reference the sldemo_mdlref_counter model that you saved locally.

  4. For each Model block, open the Block Parameters dialog box and specify the extension .slx in the Model name field. When both the model and the protected model exist in the same folder, .slxp takes precedence over .slx. If you do not specify an extension, then the original Model block in the model refers to the protected model instead of the original model. Click OK.

Protect the Referenced Model

  1. In the sldemo_mdlref_basic model, click any of the three Model blocks. On the Simulink Toolstrip Model Block tab, click Protect.

    Create Protected Model dialog box

  2. In the Create Protected Model dialog box, select the Simulate and Use generated code check boxes. These options allow the protected model user to simulate and generate code for a model that references the protected model. If you want to password-protect the functionality of the protected model, enter a password with a minimum of eight characters. Each option can have a unique password.

  3. If you have Embedded Coder and specify an ERT-based system target file (for example, ert.tlc) for the model, the Code interface field is visible.

    In this example, sldemo_mdlref_basic does not specify an ERT-based system target file, therefore the Code interface options are not available in the Create Protected Model dialog box.

    From the Code interface drop-down list, select one of these options:

    • Model reference — Specifies code access through the model reference code interface, which allows use of the protected model within a model reference hierarchy. Users of the protected model can generate code from a parent model that contains the protected model. Users can run Model block SIL/PIL simulations with the protected model.

    • Top model — Specifies code access through the standalone interface. Users of the protected model can run Model block SIL/PIL simulations with the protected model.

  4. From the Content type list, select Obfuscated source code to conceal the source code purpose and logic of the protected model. For more information on the model protection options, see Content type.

  5. Expand the Tunable parameters for simulation section and select the parameters that you want the protected model user to be able to tune during simulation.

    For code generation, parameters with non-auto storage classes are tunable. For more information, see Storage Classes for Parameters and Signals Used in Model Blocks.

  6. In the Destination folder box, specify the folder path for the protected model. The default value is the current working folder.

  7. To automatically collect, create, and package supporting files with the protected model, set Contents to Protected Model (.slxp) and dependencies in a project.

    Note

    Before sharing the project, check whether the project contains the necessary supporting files. If supporting files are missing, simulating or generating code for the related harness model can help identify them. Add the missing dependencies to the project and update the harness model as needed.

  8. Setting Contents to Protected Model (.slxp) and dependencies in a project selects the Create harness model for protected model check box. The harness model is included in the project and provides an isolated environment for the Model block that references the protected model.

    Harness model with model block that references the protected model sldemo_mdlref_counter.slxp.

  9. To further customize your protected model, you can:

  10. Click Create.

    A project archive (.mlproj) that contains the protected model, harness model, and supporting files appears in the specified destination folder. To test the protected model, extract the contents of the project archive by double-clicking it in the Current Folder browser and specifying the destination folder. Alternatively, right-click on the project archive and click Extract Here. The project opens, and the extracted files are in a new folder named after the project archive.

  11. When you create the protected model from the Simulink Editor, a protected model report is generated and included as part of the protected model. For this example, to view the protected model report, double-click the protected model or right-click the protected-model badge icon on the block in the harness model and select Display Report.

    Protected Model report for sldemo_mdlref_counter.

    The report contains:

    • A Summary, including the following tables:

      • Environment, providing the Simulink version and other product versions and the platform used to create the protected model.

      • Supported functionality, reporting On, Off, or On with password protection for each possible functionality that the protected model supports. If you configure your protected model for multiple targets, this table includes a list of supported targets.

    • An Interface Report, including model interface information such as input and output specifications, exported function information, interface parameters, and data stores.

    The report does not contain other sections that appear in a code generation report for non-protected models, such as a code metrics report and traceability report, because these reports include more information about the model's design.

  12. You can test the protected model to compare it to the original model. For more information, see Test Protected Models.

  13. To use the protected model in a model hierarchy, reference it through a Model block such as the one included in the harness model. The Simulation mode for Model blocks that reference a protected model is set to Accelerator. You cannot change the mode. For more information, see Reference Protected Models from Third Parties.

Other Methods of Protecting Models

To create a protected model from the current model, use one of these options:

  • On the Simulink Toolstrip Simulation tab, click the Save button arrow, then select Protected Model.

  • On the Simulink Toolstrip C Code tab, click the Share button arrow, then select Generate Protected Model.

To programmatically create a protected model, use the Simulink.ModelReference.protect function.

Protected Model Requirements and Limitations

When you create a protected model, consider these following requirements:

  • You must have a Simulink Coder™ or HDL Coder™ license to create a protected model.

  • The model must be available on the MATLAB® path.

  • The model cannot have unsaved changes.

  • The model uses the configuration that is active during protection. You cannot change the configuration of a protected model.

  • If the model contains variants, the protected model includes only the variant that is active during protection.

  • The model protection process does not preserve callbacks. For more information on creating callbacks for use with a protected model, see Define Callbacks for Protected Models

  • Do not rename the protected model or change its suffix. If you do so, the model is unusable until you restore its original name and suffix.

  • Use a unique name for the model and for models that it references. If a protected model references a model that shares a name with either a different protected model or a different model within the hierarchy of another protected model, there are limitations for using the protected models. If a top model references two protected models that have such a naming conflict, you cannot protect the top model, generate code for the top model, or simulate the top model in software-in-the-loop (SIL), processor-in-the-loop (PIL), or rapid accelerator modes.

  • If your model includes a non-inlined S-function, use a unique name for the .MEX file. If there is a name conflict with a different .MEX file on the MATLAB path, you cannot simulate the protected model.

The model must also meet the requirements listed in Model Reference Requirements and Limitations.

Code Generation Requirements and Limitations

To create a protected model that supports code generation, the model being protected must meet these requirements:

  • The model must use normal, accelerator, software-in-the-loop (SIL), or processor-in-the-loop (PIL) modes and a single target.

  • The model must not include noninlined S-functions.

  • The model must not have the Code Generation > Verification > Measure function execution time configuration parameter selected. If this option is selected when you protect a model, the software turns off the parameter and displays a warning.

  • Protected referenced models must support code generation without password protection.

  • The model must be compatible with the Content type of each protected referenced model. This table provides compatibility information.

    Code Generation Content Type Compatibility

    Protected Parent Model Content TypeCompatible Protected Referenced Model Content Types
    Binaries

    • Binaries

    • Obfuscated source code

    Binaries with 'ObfuscateCode' set to 'false'

    • Binaries

    • Binaries with 'ObfuscateCode' set to 'false'

    • Obfuscated source code

    • Readable source code

    Obfuscated source code

    • Obfuscated source code

    Readable source code

    • Obfuscated source code

    • Readable source code

    When the Content type of the protected parent model and protected referenced models do not match, code generation applies the Content type that provides the higher level of protection. For example, a protected parent model set for Binaries generates Binaries for protected referenced models that are set to Obfuscated source code. A protected parent model set for Readable source code generates Obfuscated source code for protected referenced models that are set to Obfuscated source code.

To avoid an error during code generation of a model that includes a protected model:

  • The protected model name must be unique from other model names in the same model reference hierarchy.

  • The interfaces must match.

  • The parameters must be compatible.

Nested Protected Model Requirements and Limitations

To enable a recipient of your protected model to protect a model that references it, your protected model must:

  • Support accelerator mode. You must select Simulate in the Create Protected Model dialog box or set 'Mode' to 'Accelerator' or 'CodeGeneration' using the Simulink.ModelReference.protect function.

  • Use the default 'CodeInterface' setting: 'Model reference'.

  • Not use password protection for simulation.

  • Not have callbacks.

  • Support without password protection the operations that the protected parent model is intended to support.

  • Use a Content type that is compatible with the intended Content type of the protected parent model if the protected parent model is intended to support code generation. For a list of compatible Content type options, see the table in the preceding section.

  • Use the same compiler as the protected parent model is intended to use.

  • Not reference a model that shares a name with either a different protected model or a different model within the hierarchy of another protected model.

If the model that you want to protect references a protected model, the referenced protected model must meet the preceding requirements.

When you protect a model that references a protected model, you must specify the tunable parameters of the referenced protected model as tunable for the model you are protecting.

Note

A protected model that you create with the Use generated HDL code option selected allows encryption and support for simulation and HDL code generation from a model that references the protected model. You cannot obfuscate the HDL source code, have callbacks, or use nested protected models with this option. To learn more about HDL code generation limitations, see Protected Model Restrictions for HDL Code Generation (HDL Coder).

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