[lxgr]

Yes, stored value cards are a very mature technology.

For various reasons, they're mostly used in closed-loop systems these days (think laundromats, transit systems etc.), but historically there were open-loop deployments in many European countries, and in some countries, stored-value POS payments are still very popular, e.g. in Japan.

It's a real shame that the entire world moved to online-only. Sure, it's much easier and there's less opportunity for various kinds of fraud as a result, but in terms of availability during outages or cyber attacks, it was a big unforced step backwards.

[Galanwe]

> historically there were open-loop deployments in many European countries

Indeed, there used to be things like "Moneo". The problem is that banks never trusted really these systems, so you were limited to, say, 50E of stored value. Also for some reason in Europe the readers of such cards have never been great, I guess because most devices were built on the cheap, so even if the transaction is offline and supposedly fast, you would have to wiggle your cards all around most readers for 2s until it's picked up.

In Hong Kong there is the Octopus card, which started as a closed loop subway card, but ended up being so loved that now you can pay litterally anything with it. It can store up to $500, and you can set it up to automatically top-up to $500 more per day linked to your bank account. Also accepting payments from octopus cards is very easy, you don't need a physical device and small businesses can just have the customer card tapped on their phone with a merchant app.

[mytailorisrich]

Stored values cards were the way French public phone booths worked when they first moved away from coins in the 80s.

There were single-use chip cards that you bought and kept in your wallet. Plain eeprom.

I remember I built a reader for them as a teenager...

[lxgr]

These were storage only though, right? Such systems are trivial to compromise.

Stored-value payment cards usually contain at least a secret key and some logic that allows them to establish a secure channel to another trusted entity, such as a merchant smartcard (which can be embedded in a terminal) or a backend server (and a corresponding HSM).