I am late to comment and your edits may cover this but I think:
The problem is too flexible where “memory wipe” could wipe any possible way for you to know the signal you are looking to trust
and
“malicious party” can be flexible enough to always win.
Any signal that you were trying to hide in your environment might be detected by a “malicious entity” and interfered with; and any signal that might be hidden inside your brain might be wiped, depending on your definition of each part; it may be impossible to defeat the challenges.
I am late to comment and your edits may cover this but I think:
The problem is too flexible where “memory wipe” could wipe any possible way for you to know the signal you are looking to trust and
“malicious party” can be flexible enough to always win.
Any signal that you were trying to hide in your environment might be detected by a “malicious entity” and interfered with; and any signal that might be hidden inside your brain might be wiped, depending on your definition of each part; it may be impossible to defeat the challenges.