tramp-yn-prompt-regexp

tramp-yn-prompt-regexp is a variable defined in `tramp.el'.
Its value is

"\\(\\(?:Store key in cache\\? (y/\\|Update cached key\\? (y/n, Return cancels connectio\\)n)\\)\\s-*"

Documentation:
Regular expression matching all y/n queries which need to be confirmed.
The confirmation should be done with y or n.
The regexp should match at end of buffer.
See also `tramp-yesno-prompt-regexp'.

You can customize this variable.