How do I get obfuscated text using the font parameter in raw JSON text?

There are two ways to make illegible text:

• {"text":"You aren't going to read this in a million years.","obfuscated":true}  
  

  This is the most common way of creating scrambled text. This will scramble the letters normally.

• {"text":"Wait, are you actually trying to translate this?","font":"minecraft:alt"} 
  

  The minecraft:alt font is the font used as decoration in enchantment tables. This doesn't make the text constantly scramble. You could use this as a translation challenge in a map.

Those are the two ways of making illegible text. You could combine them, like so:

{"text":"You aren't going to read this in a BAZILLION years.","obfuscated":true,"font":"minecraft:alt"}

and that would make sure that no one finds out what the text says, ever.
^{(unless they look at the commands)}