Origins of NFC
The technology originated as an offshoot of RFID tech, or radio frequency identification, with the added rule that the devices had to be close to each other physically. Both techs rely on the physics of electromagnetic radio fields to transmit parcels of data. The term “radio wave” is used to denote a certain swath of wavelengths of light, and it’s used in most modern technologies as a means of communication because it can easily go through walls and generally not be hampered by physical obstacles (as opposed to, say, visible light).
How do NFC readers work?
Kisi Reader with NFC card
The door reader activates and transmits radio waves to induce electric current in the NFC card; passive devices don’t actually need any power source, but instead are built to activate and begin transmitting their NFC signal when exposed to a changing magnetic field.
The active devices will have an electric current running through them and, when they are put in close proximity to a passive device, they will prompt it to begin transmitting—read the signal—then the passive device will stop transmitting when it’s moved farther away.
Here’s a diagram explaining how the induced current works. The active device (right: “Reader”) has its magnetic field interact with the passive device (left: “Smartphone”) and creates a matching current to power it.
Different Types of NFC ID
The NFC reader induces a magnetic current in the token and, in turn, the token transmits the relevant string of characters. Depending on what type of token it is, the nature of this string will change: If it’s a simple ID reader, then the string is a unique identifier for the user; if it’s a transit card then it’s an ID, but on the back end the reader needs to record the charge and update its server, and if it’s a contactless payment card, then it’s an ID with many added layers of encryption and security to protect the user’s bank information (in this case, only a dedicated and approved reader could decrypt the information relevant to the bank details, any other reader would only be able to read a simple ID string).
