Now that coronavirus vaccines are starting to roll out in the US and abroad, many people may be dreaming of the day when they can travel, shop and go to the movies again. But in order to do those activities, you may eventually need something in addition to the vaccine: a vaccine passport application. Several companies and technology groups have begun developing smartphone apps or systems for individuals to upload details of their Covid-19 tests and vaccinations, creating digital credentials that could be shown in order to enter concert venues, stadiums, movie theaters, offices, or even countries. The Common Trust...