rfid.wtf / WTF is RFID?

WTF is RFID?

Radio, a number, and a lot of plastic. Pick a way in — every path ends up in the same places, and anything you've already read gets a ✓.

Start from the physics

What radio is, what "ID" means, and why the frequency changes everything.

  1. What is RF?Radio frequency — electricity that wiggles fast enough to leave the wire.Concept
  2. What is the ID?Most RFID is a radio-powered barcode. The interesting part is what happens after.Concept
  3. LF, HF, UHFThree slices of the radio spectrum, three completely different kinds of RFID.Concept

Start from what's in your pocket

Pick a thing you've tapped, and work backwards to how it works.

Contactless credit cardsTap to pay is a tiny smart card doing cryptography in the half-second your card hovers over the terminal.In the wildHF · 13.56 MHzHotel door keysA card that stores a room number and a checkout time, read by a lock that isn't plugged into anything. That design explains almost everything odd about hotel keys.In the wildHF · 13.56 MHzOffice badgesThe badge you tap at work is usually just a number. Everything interesting happens in a box in a closet.In the wildClothing and inventory tagsThe strip of foil in your T-shirt label. It doesn't just say "medium blue shirt" — it says which one.In the wildUHF · 860–960 MHzPet microchipsA grain-of-rice LF tag that says one number. Whether it gets your pet home depends entirely on a database.In the wildLF · 125–134 kHzBiohacking (human implants)The same grain-of-rice glass chip as the dog, injected into the web of your hand. A hobbyist access badge you can't lose — and can't upgrade without a scalpel.In the wildSecurity keys (YubiKey)The thing on your keychain that logs you in with a tap — a smart card in a different shape.In the wildHF · 13.56 MHzE-passportsThe chip behind the little camera-shaped logo — signed by your government, and built not to talk to strangers.In the wildHF · 13.56 MHzPhonesYour phone is a reader, a card and a wallet — sometimes all in the same minute.In the wildHF · 13.56 MHzMobile walletsApple Wallet, Google Wallet and friends — one tap for your card, your train, your car and your office, and not one of them is the real thing.In the wildHF · 13.56 MHzToysYoto cards, Skylanders, amiibo and DropMix — RFID's most fun job, done two very different ways.In the wildHF · 13.56 MHz

Start from your tool

Got a reader, a phone or a Proxmark? Pick it and every page shows tips for it.

Proxmark3The open-source RFID research tool — LF and HF, a command line, and the deepest rabbit hole on this site.ToolFlipper ZeroThe pocket multi-tool with a dolphin on the screen — 125 kHz and NFC in a friendly menu.ToolChameleonUltraA keyring-sized LF/HF card emulator with a reader built in, driven from a phone app.ToolYour phoneThe NFC reader you already carry — great at HF, blind to everything else.ToolUSB NFC readerA cheap desktop 13.56 MHz reader — the developer's way into HF cards, scripts and smart-card tools.ToolUHF readerThe only thing that can see EPC tags — from a USB stick on your desk to a handheld that counts a shop in an hour.Tool

The whole map

Arrows point from a page to what builds on it; dashed arrows are ways in from examples and tools. Colour is the band (LF, HF, UHF, tools), dashed boxes are drafts, ✓ is read. Click anything.

LF · 125–134 kHz

LF — 125 kHzHID ProxPet microchips

HF · 13.56 MHz

HF — 13.56 MHzISO 14443NFC and NDEFMIFARE ClassicMIFARE DESFireiCLASSSeosPublic-key cardsPIV and CACMIFARE DUOXContactless credit cardsHotel door keysSecurity keys (YubiKey)E-passportsPhonesMobile walletsToys

UHF · 860–960 MHz

UHF — 860–960 MHzClothing and inventory tags

All bands

What is RF?What is the ID?LF, HF, UHFNear field vs far fieldUltra-wideband (UWB)The UIDWhy old cards are a bad ideaWiegandOSDPMulti-technology readersMobile credentialsAliroOffice badgesBiohacking (human implants)

Tools

Proxmark3Flipper ZeroChameleonUltraYour phoneUSB NFC readerUHF reader