Not password protected but you can hide the edit button, by tagging the tiddler with a certain tag, e.g "noedit" and then make a stylesheet tiddler like so
title: $:/mystylesheet
tags: $:/tags/Stylesheet
text:
.tc-tagged-noedit .tc-image-edit-button {display:none;}
Note that you, yourself, will also not access the edit button then. But if you edit the stylesheet you'll get it back, and you can relatively easily make a toggle using my just released toggle macro to set the values "none" and "inline" in some field and then have that last line instead read
.tc-tagged-noedit .tc-image-edit-button {display:{{yourtoggletarget}}; }
Note you must also set the type of the stylesheet tiddler (i.e the dropdown just below the editor field) to be for TW5, in order for the stylesheet to understand this.
<:-)