Lecy relies on dynamic NFC: at every scan, the tag generates a unique, encrypted, short-lived link. That link is only valid for that visit, in front of that tag, at that moment. It is tamper-proof proof of presence, where a QR code or a classic NFC tag always carries the same address, which can be photographed and shared. This article explains the difference, why it matters for loyalty, and what Lecy adds on top.
The problem with the fixed address
A QR code is an image that encodes a web address. A classic NFC tag does the same thing by radio: it transmits a fixed address. In both cases, the address is always the same. It only takes photographing it, copying it or sharing it in a group chat for anyone, anywhere, to open the link and earn points without having set foot in the shop. This is not a theoretical flaw: it is why QR-code programmes end up adding checks (a code to type, staff validation), that is to say friction, to compensate for an address that cannot be protected.
What a dynamic tag does
Lecy's tag computes a different address at every read. The link contains an encrypted signature, produced by the chip at the moment of the scan, which the server verifies before awarding the point. A link that has been used is worthless. A copied link is worthless too, because it matches no future scan. The only way to obtain a valid link is to hold a phone in front of the tag: that is what we call proof of presence. For the customer, nothing changes: they hold up their phone, they open the link. For the shopkeeper, everything changes: a point corresponds to a real visit.
The point comes from the phone, not from staff
The most common fraud in loyalty is not the customer's, it is the human gesture: the friendly stamp, the point added "as a favour", the card validated without a purchase. Any solution where a person awards the point opens that door. With Lecy, the point is triggered by the customer's phone on the tag. The team does not intervene, so the team can neither make a mistake nor do a favour. Manual awarding exists, for an event or a phone that does not read the tag, but it is logged in the back office and remains the exception.
The delay between two points
A customer could scan twice in a row. The back office sets a minimum delay between two points, three hours by default, adjustable by the shopkeeper. Before that delay has passed, a new scan adds nothing. This setting completes proof of presence: the first guarantees the customer is there, the second that "there" only counts once per visit. Setting this delay to zero would break that logic; it is not recommended, even for a special event.
Where this technology comes from
NFC tags with dynamic signatures are not new: they have protected products against counterfeiting for years and serve to prove that an agent did visit a given place, in industry and maintenance. What Lecy does is apply that proof of presence to loyalty in a local shop, where it was not used, and make it invisible to the customer. We do not claim to have invented the technology; we put it where it was missing.
What it changes, concretely
A shopkeeper who offers a reward every ten visits knows that ten visits took place. A network head office comparing its sites compares real visits. The dashboard numbers (visits, active members, rewards unlocked) are measurements, not declarations. And the customer did nothing more than hold up their phone.
Frequently asked questions
Can a customer share the link with a friend so they earn a point?
No. The link is only valid for the scan that produced it and it is consumed when opened. A passed-on link awards nothing.
What happens if the customer scans three times during their visit?
The first scan adds the point. The following ones, within the minimum delay, add nothing.
Can the tag be copied?
The signature is computed by the chip at every read, from a key that never leaves the chip. Reading the tag gives nothing that would allow reproducing it.
Next article: your terms, your rewards, your colours. For the full comparison with the QR code, the paper card and the app, see every comparison question.