Your butthole is like a snowflake: No two are exactly alike. At least, that's the crux of a new scientific paper outlining the mechanisms for a smart toilet that identifies poopers based on video clips of their unique anuses.
https://www.vice.com/en_us/article/jge377/stanford-smart-toilet-uses-butthole-for-identification
https://www.vice.com/en_us/article/jge377/stanford-smart-toilet-uses-butthole-for-identification