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One of the issues Josh and I talked about at Blackhat was how the SSL certificate warning message can be used to gain information about a user’s behavior and how that can be used against the user. Let’s say a man in the middle causes an error via proxying a well-known owner/subsidiary. For example let’s say https://www.youtube.com/ which most technical people know belongs to Google and which, incidentally causes SSL/TLS mismatch errors because it’s mis-configured. Experts who see such an error and investigate will think it’s just a dumb (innocent) error. Non-experts will click through immediately, because they always do when they see such things.
By measuring the wait time the attacker can know which type of user the victim is - a technical one, or a novice. If the user is a novice the attacker knows they don’t have to worry anymore - they can deliver their snake oil cert later if the user goes through it quickly because that user’s behavior will most likely stay the same. Of course figuring out the timing might be a bit tricky because really new users will be awfully confused by cert warnings and will seem “slow” I’d bet. Anyway, something to investigate further.