notebooks – Locking cell groups

Imagine I have a notebook divided into multiple groups of code cells which are set as initialization groups. I then have a single cell which evaluates a function program() that yields an interactive tool (for example via Manipulate) which internal functions are defined in the initialization groups. Something like

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If these groups are collapsed, is it possible to lock them so that when I share the notebook the code in these groups remains hidden and private and the only accessible cell is the one to run the program?