Holding a QR code up to a scanner is second nature to many people these days. From digital boarding passes to proof of purchase, they have become ubiquitous in an increasingly paperless world.
So it requires no great leap of the imagination to picture British people beeping themselves into stadiums and pubs with a little black and white square that proves they have been vaccinated against Covid. Are they not the obvious solution to get the country's hospitality and entertainment industries open again?
The reality is far more complex and, for every question that vaccine passports (or certificates, as the Government prefers) appear to answer, they pose many more. Yet, as the Government knows all too well, it's not an issue that can just be left for the market to decide.
Perhaps the first question facing vaccine certificates is when exactly to introduce them. The first option would be to do so as soon as possible, but this would create a scenario in which only a select slice of society would have access to reopened services.
"If we were going to introduce this tomorrow, which isn't the plan, you'd exclude everyone 65 and under," says Melinda Mills, a professor of demography at Oxford University and a lead author of a Royal Society report on the criteria vaccine passports would need to meet.
Such a move would be ethically dubious and "not particularly handy, due to excluding age and other groups, for the economy", she says.
But the more likely option of waiting until everyone eligible has been offered a jab still leaves plenty of problems.
Because vaccine hesitancy is highest among certain ethnic minority groups, certificates would "exclude an already disadvantaged group and one that's a large proportion of essential workers," says Prof Mills.
And that's before you get on to the list of people who are excluded for medical reasons, including pregnant women and the immunocompromised, and people who refuse vaccines for religious and political reasons.
Children, on whom vaccines are only now being trialled, are another problem area.
In Israel, where the world-leading pace of vaccination has slowed, so-called "green passports", given to those who have received two vaccine doses, have been proposed as an incentive to increase uptake.
"Decide whether you are part of the celebration or whether you will be left behind," Yuli Edelstein, the health minister, declared on Twitter.
Yet whether such a programme would actually work is far from clear. "Where there are uptake issues, these seem to be related as much to wider questions of access to the vaccination and of social exclusion more generally than to vaccine hesitancy," says Robert Dingwall, a professor of sociology at Nottingham Trent University.
"A vaccine passport is a sanction rather than an incentive."
Indeed, to make vaccine certificates work among communities with low uptake would require the same kind of careful and delicate communication efforts that were already necessary to boost vaccine uptake. It's the kind of work that Israel has had to undertake to combat misinformation and vaccine hesitancy among the country's large Orthodox Jewish population.
Without it, says Prof Mills, vaccine certificates risk playing into the same problems that vaccines face. Among the reasons for low uptake in certain communities, she says, are a lack of trust and "a history of problems dealing with medical authorities and issues like the Windrush scandal". If the communication isn't done right, "this could backfire quite quickly", she adds.
Waiting until the vast majority of the population has been inoculated also raises questions about whether vaccination certificates are of much value anyway. "In a vaccinated population, they do not actually convey any information that is helpful," argues Prof Dingwall.
Yet leaving the issue unresolved is not a solution either. While the state may not wish to find itself discriminating against ethnic minorities, private businesses will face the countervailing pressure to keep their employees and customers safe. Which side the law would come down on is not yet clear.
A business-led approach wouldn't just raise ethical questions but also practical ones. Without clarity from the Government, the onus may fall on individual employees, says Prof Mills, "and that's unfair on the person at the door who has to say 'no, I'm not serving you'."
Not that banning vaccine requirements outright would be entirely clear cut either. While vaccine uptake is generally good in the UK, it's worryingly low among care home staff. Should vaccines be mandatory for medical and care workers? As Prof Chris Whitty, the chief medical officer, pointed out earlier this month, surgeons are required to have a hepatitis B vaccine.
Beyond the grand questions, technical ones arise too. Where would passports apply? Surely not at essential services? Can they be made safe, secure and counterfeit-proof? Will they expire if immunity fades? Could they be revoked if a vaccine-resistant variant emerged?
Many of those smaller questions are answerable, but the Government will need a response to those much larger social questions too – or it risks a chaotic patchwork of homemade rules taking root.