Depending on the target application, there are few totally different approaches for designing NFC tags. Naturally, the higher are the feature requirements for the NFC tag platform, the higher would be the price for a single tag.
When choosing the appropriate platform, it’s always worth carefully reviewing the project and trying to minimize the feature expectations, just to optimize the costs as much as possible.
For instance, the requirement for asymmetric authentication can be very often replaced with a clever use of symmetric authentication. This is not always the case, but it applies to some of the applications. Thanks to such a redesign, it is possible to choose an NFC platform which is a few times cheaper, so it’s definitely worth considering.
NFC Platform Comparison
|NTAG® 213, NTAG® 215, NTAG® 216||NTAG® 424 DNA||JavaCard||Custom hardware|
|Approx. price per tag||$0.2||$0.3||$1.5 - $3||$3 - $10|
|Storing data on the tag||144-888 bytes||416 bytes total||depending on the chip, from 1 to 120 kB||arbitrary storage depending on hardware used|
|NDEF tag behavior||✔️||✔️||✔️||✔️|
|Dynamic URL feature||✔️||✔️||✔️||✔️|
|Cryptographically secure dynamic URL feature||✔️||✔️ (can be emulated similarly)||✔️ (can be emulated similarly)|
|Symmetric authentication (AES)||✔️||✔️||✔️|
|Asymmetric authentication (RSA/ECC)||✔️||✔️|
|Custom business logic||✔️||✔️|
|Executing heavy algorithms||✔️|
|Non-mainstream cryptographic algorithms||✔️|
NTAG® 213 (as well as NTAG® 215, NTAG® 216) is a very simple but also extremely cheap model of NFC tags. Useful for applications where security is not very important, but it’s required to deploy a massive amount of tags.
NTAG® 424 DNA
One of the cheapest cryptographically-secure platforms currently available on the market. Supports symmetric authentication using AES and the dynamic URL feature with AES-CMAC signatures. Suitable for security applications.
Note: This site is not affiliated with NXP. Information is provided here for descriptive purposes. NTAG — is a trademark of NXP B.V.
Used mostly for credit cards and phone SIM cards. Can be also used to create NFC tags. Allows to implement complex business logic and custom NFC commands. Moreover, it supports asymmetric cryptography, including SHA-256, RSA and ECC algorithms. While not as cheap as NTAGs, it is able to cover most of the applications except the extremely demanding ones.
Suitable when you want to run heavy algorithms or non-mainstream cryptography on the tag itself. The cost is significantly higher, but the custom tag could fit any application that is physically possible to implement. In most cases, it would be optimal to use some low-power general purpose microcontroller (AVR or ARM) and attach it to I²C - NFC bridge (for instance NTAG 5 Link/Boost).
There are a few different solutions for implementing an NFC tag. They fall into different price ranges, also having different feature sets and requiring totally different approaches in general. It’s worth carefully designing the solution, not to overpay for the features that won’t be used or are not needed.