Help, I do not understand how I can install a cryptographic key before compiling godot Windows 7, VS 2017, Godot 3.1
Did you use this service? You're supposed to select aes-256-cbc when generating your key. Here's documentation from Godot on script encryption.
Problem solved. From the Visual Studio console, you had to enter
SET SCRIPTAES256ENCRYPTIONKEY = yourkey
SET SCRIPTAES256ENCRYPTIONKEY = "yourkey"