add ibutton

README.md

@@ -10,3 +10,4 @@ Kickstarter page: [kickstarter.com](https://www.kickstarter.com/projects/flipper
 
 * [Sub-1 GHz radio](wiki/sub-1ghz-radio.md)
 * [125 kHz RFID](wiki/125khz-rfid.md)
+* [iButton contact keys](wiki/ibutton.md)

wiki/ibutton.md

@@ -0,0 +1,3 @@
+# iButton contact keys
+
+Flipper Zero has a built-in 1-Wire pad to read iButton (DS1990A) keys, also known as TouchMemory or Dallas keys. This technology is quite old but still widely used around the world. It's based on 1-Wire protocol and doesn't have any authentication, so Flipper can easily read these keys, save IDs into the memory, write IDs to blank keys, and emulate the key itself.