This is a paid asset, but now you can download Obfuscator Free.
Detail this asset from Unity Asset Store: Original Link
Obfuscator v3.8.2 (Latest version)
This asset obfuscates your code to make it harder for bad guys to reverse engineer your projects. Specifically designed for Unity, it seamlessly links in with its build process.
The top priority of this package is to work straight out of the box with no extra steps required. While other obfuscators can stop a game from working, Beebyte’s obfuscator looks for specific Unity related code that must be protected. The contents of your source files are unchanged, the obfuscation targets the compiled assembly.
– Supports IL2CPP
– Supports Assembly Definition Files (Unity 2017.3+)
– Removes Namespaces without any conflicts
– Recognises Unity related code that must not be changed
– Renames Classes (excluding MonoBehaviours†)
– Renames Methods
– Renames Parameters
– Renames Fields
– Renames Properties
– Renames Events
– String literal obfuscation
– Adds fake methods
– Easy and extensive customisation using the Unity inspector window
– Consistent name translations are possible across multiple builds and developers
– Semantically secure cryptographic naming convention for renamed members
The asset works for both Unity Free and Unity Pro version 4.2.0 onwards (including Unity 5, 2017-2020). Build targets include Standalone, Android, iOS, WebGL, UWP. Other platforms are not guaranteed or supported but may become supported at a future date.
† MonoBehaviour classes can be renamed up to and including Unity 2018.1. However this feature had to be retired with 2018.2 onwards.
Why not complement your security with the Anti-Cheat Toolkit – a great third party asset.
For more information about the Obfuscator, please see the FAQ