make NDEF configurable

APPLICATION.MD

@@ -8,7 +8,9 @@ compared to the previous released version. This is version 2.0 of the specs (unr
 ### Changes since 1.2
 * **BREAKING** Removed assisted key derivation
 * **BREAKING** Removed plain data signing, now only 32-byte long hashes can be signed
-* Added internal key generation
+* Added internal key generation (GENERATE KEY)
+* Added the ability to customize the NDEF response (SET NDEF)
+
 
 ## Overview
 
@@ -152,6 +154,23 @@ if P1 = 0x00:
 if P1 = 0x01
 - a sequence of 32-bit numbers indicating the current key path. Empty if master key is selected.
 
+### SET NDEF
+
+* CLA = 0x80
+* INS = 0xF3
+* P1 = 0x00
+* P2 = 0x00
+* Data = the data to store
+* Response SW = 0x9000 on success, 0x6A80 on invalid data
+* Preconditions: Secure Channel must be opened, PIN must be verified
+
+Used to set the content of the data file owned by the NDEF applet. This allows changing the behavior of Android and other
+clients when tapping the card with no open client. As an example, it could be used to launch a specific wallet software.
+
+The data is stored as is. A check is made that the first 2 bytes, read as a MSB first short, are equal to the Lc field
+minus 2 (the length of the field itself). This does not ensure that the NDEF record is valid, but ensures that no out
+of bound access happens.
+
 ### VERIFY PIN
 
 * CLA = 0x80