At least in UK the app will generate a new certificate on the fly.
Since the French app is pretty terrible (it used to be the barely functional contact tracing app that didn't want to use Google/Apple's API, so there's a pretty strong popular stigma against it), even a sizeable portion of smartphone users use an alternative too (I personally have my QR code in Apple's Wallet, but there are other 3rd party solutions).
Depending on when that key was in use, this may be an epic bureaucratic mess to solve here in France if they have to reissue many.
Edit : I'll quickly add that while there's a database of vaccinated people handled by CNAM (the single payer social security administration), it doesn't seem extremely accurate : my best friend and one of his collegues were vaccinated, issued a QR code, but they weren't added to said database and had a terrible time getting the situation fixed. In the end, a pharmacist reissued a "vaccination" for them to "get them in the system". So that database is probably at best incomplete (for the process of reissuing).
There is however a prevalent issue with QR code scanning that I noticed twice personally (and friends reported the same experiences at other places), which is that most restaurants use a super cheap phone/tablet with a terrible camera that usually is unable to focus on a smartphone screen correctly.
Once, the person was honest about it and explained they kept having issues with it, and I tried to help him focus correctly his device (QR code size + luminosity seems to be the issue from what I saw).
The second one tried a couple of time, didn't manage to focus and told me "all ok" despite it's device not having scanned me (I could see the screen).
If I had to travel though, I'd definitely take the paper certificate on top of it, as, at least here in France, that's considered for better of for worse the source of truth.
1. Scan the code with the app every time.
2. Ask if I have the pass, maybe look at it once, hopefully remember me the next times.
There is also a small percentage of cases of no questions asked, ever.
By the way, I'm using a printed copy of the pass. It never runs out of battery, I don't mind if it falls on the floor when I'm using it, it works even if I'm using the phone for something else. Cons: it needs to be replaced if its key gets revoked.
In Ireland it’s hit and miss. About 60% of the time had to produce it, but very few places want to see ID as well, which is needed to prevent people just using someone else’s pass.
I’m all for it so I’d love to see better enforcement.
Yeah the UK very wisely put the passports and the contract tracing in separate apps (helps that the NHS already had an app pre-pandemic). Not sure if it was intentional, but it certainly sidesteps this issue!
The certificate I am using is printed on a piece of paper I carry with me.
Just out of curiosity, is that for privacy reasons or ? Seems rather strange for a smartphone ?