Set up an NFC tap tag

A tap tag is a small NFC sticker or card at your counter. A customer holds their phone to it, and their stamp request arrives at your till with a chime, just like a scan of the till poster. Someone on your team still approves every stamp.

If you’d rather not use tags, the till poster does the same job with the camera. Three ways to give a stamp compares them.

Two kinds of tag

• Any NFC sticker (NTAG 213, 215 or 216, the kind most shops sell). It holds your till poster’s link, so a tap does exactly what scanning the poster does. Like the poster’s, its link works from anywhere, so your team’s check of the code is what stops a request from someone who isn’t there.
• A secure tag (NXP NTAG 424 DNA). It signs every tap, so a request from it always started with a tap at your counter. It takes more setting up, with keys from NextStamp.

Ordinary NFC stickers

1. Open Overview, tap the card under Loyalty cards and scroll to Posters. On a till poster, tap Copy NFC sticker link. If you want to replace the sticker on its own later, make a till poster just for it first (New poster, kind Till poster).
2. Write the link on the sticker as a web address with an app such as NFC Tools (iPhone and Android) or NXP TagWriter (Android).
3. Lock the sticker. In NFC Tools, that’s Other, then Lock tag. Locking can’t be undone, and without it anyone with an NFC app could change the link on your counter.
4. Tap it with your phone. The card’s page opens, just as when you scan the till poster.

If you replace that till poster, the sticker stops working with it. Write a new sticker with the new link.

Secure tags: what you need

• The right tags. Stickers or cards with NXP’s NTAG 424 DNA chip. It signs every tap, which is what makes a tap impossible to fake.
• An app to write the tag. On iPhone, NFC.cool Tools. On Android, NXP TagWriter. On Windows, GoToTags Desktop with a USB NFC reader. Your tag supplier can also write the tag for you with the link, settings and keys NextStamp gives you.
• A live card and an outlet. Tap tags appear on a card’s page once the card is published, and each tag belongs to one outlet where the card works.

Owners, admins and managers can add tags. Managers only see and add tags at the outlets they work at.

Create the tag in NextStamp

1. Open Overview, tap the card under Loyalty cards, and scroll to Tap tags.
2. Tap New tap tag. Give it a name you’ll recognise, such as “Counter tag” (the default), and choose its outlet.
3. Tap Create and set up. The Set up a tap tag sheet opens with everything you need to write.

A card can have up to 20 tap tags.

Write the tag

The setup sheet lists six steps. Follow them in order with the tag and your writing app:

1. Buy NTAG 424 DNA tags.
2. Write this link to the tag. Copy the link from the sheet. It ends with picc_data= followed by 32 zeros and cmac= followed by 16 zeros. The tag replaces those zeros with fresh signed values on every tap.
3. Turn on Secure Dynamic Messaging (SUN) and lock the link. Switch on the encrypted PICC data with key 1, over the 32 zeros after picc_data=, and the SUN MAC with key 2, over the 16 zeros after cmac=. The MAC input starts at the MAC itself. Then set the file’s access rights to Read: free, and Write, Read & Write and Change: key 0. Without that, anyone with an NFC app could rewrite the link on your counter.
4. Change the tag’s keys to these. Key 0 is the application master key, key 1 the SDM meta read key and key 2 the SDM file read key. Keys 3 and 4 can stay as they are.
5. Use an app to write it, or send the details to your supplier.
6. Tap it with your phone, signed in to NextStamp as yourself. Your phone says “Tag works” and the tag switches on. The sheet then says the tag works and customers can tap it.

What happens when someone taps a secure tag

• A customer with your card gets the same waiting screen as a till poster scan, with a four-character code to show your team. The till chimes and your team approves the request or says no. A tap always asks for one stamp.
• Someone new to your card who is signed in sees your card’s rules and terms, and joins with one button. With the First scan setting on “Counts as a stamp”, the button says Join and get my stamp and that same tap asks the till. Otherwise it says Start my card.
• Someone who isn’t signed in is asked to create an account (or sign in), then tap the tag again to ask for their stamp.
• Someone on your team only tests the tag. Their taps never ask for anything.

Each tap carries a counter that goes up every time. NextStamp only accepts a tap whose counter is higher than the last one it counted, and a tap refused by the card’s limits is used up too. Once a tap has asked, reloading the page or sharing its link asks for nothing. A tap that was read and never sent (an NFC app can do that) still works once, until a newer tap counts. That’s one more reason your team checks the code before approving. How NextStamp stops stamp fraud explains the other safeguards.

Only secure tags ask for stamps

A secure tag only proves where a request started if your till poster can’t ask as well. Otherwise someone at home could simply use the poster’s link. So once a card has a tag, owners and admins can switch on Only secure tags ask for stamps in its Tap tags section. With it on:

• the till poster, and any sticker holding its link, still let customers join and open their card, but never ask the till for a stamp
• customers ask by tapping the secure tag, or show their card at the till to be scanned
• a new customer’s first scan of the poster only joins them, and their first tap on the tag follows your First scan setting
• asking to use a reward from the poster works as before

The section also names any outlet where the card works but no secure tag works yet. Customers there show their card at the till.

Pause, replace or retire a secure tag

Each tag in the list shows where it stands: “Waiting to be set up”, “Working” with its last tap, or “Paused”.

• Pause stops taps giving anything until you resume it, which is handy while you move the counter around.
• Replace stops this tag now and gives a new tag new keys. You can write the same sticker again: the new tag’s setup sheet also shows the sticker’s current keys, which your app needs before it can change anything.
• Retire stops the tag for good. Customers keep their cards and stamps.

Print a sign for a tag

Each tag in the list has Print sign, for a sign that shows customers where to hold their phone. It says “Tap your phone here to collect your stamp”, with a tap mark: stick the tag behind the mark or on it. Print signs as, above the list, picks the paper, the same choice as for your posters: a poster, an A6 counter card, a landscape poster or a table tent.

Owners and admins can change the sign with Design tap signs, in the same designer as the posters (see design, print and manage your posters). A sign can carry a QR code too. It holds the tag’s plain link, so a customer whose phone doesn’t read NFC can still join and open the card. Only a real tap asks the till for a stamp.

If a secure tag doesn’t work

A customer may see one of these messages:

If your own test tap fails, check the chip is an NTAG 424 DNA and write the link, settings and keys again from the sheet. When the card screen says “Tap tags aren’t switched on for NextStamp yet”, tags aren’t available on this NextStamp service, so contact NextStamp support.