Data storage and transfer using human muscle contractions (2018)

> The information can be anything. A seemingly uncoordinated twitching finger could be a song when placed on a piano or the right pin number when placed over an input panel of a cash dispenser. Until the signal is not decoded, even the carrier is clueless about its meaning.

Is that true? I've never heard of 'muscle memory' being an actual memory like that...

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However, I'd like to point out that there is in fact a well-established kind of memory which lets you use a human to carry a large amount of memory while being 'clueless' about not just its meaning, but what the encoding even is: visual recognition memory.

You can recognize whether you've seen an image before; given appropriate datasets, this allows encoding messages into a human's visual recognition memory without them being able to elicit this knowledge in the absence of the target images. This can be used for tricks like storing passwords, or multiplying 10-digit numbers: https://people.csail.mit.edu/andyd/rec_method.pdf I calculate that you could feasibly store 5.8 kilobits per human: https://www.gwern.net/Spaced-repetition#fn61

If this works then this would be a way to store passwords or private keys unconsciously in the muscle memory of the only person who should have access to them.