HCE - Is there a way to manipulate the ATR?

Question

I am making a Host Card Emulation app on Android, everything works fine with my PC/SC reader. I am able to send APDU commands and get the reponses. Now I want to know if it's possible to manipulate the ATR of the card emulated by Android using Android's NFC library (or not)? I have looked into the documentation but there's nothing about the ATR, does Android generate it automatically for each device?

Answer 1

Yes, Android generates the answer-to-select (ATS) automatically. There is no Android API to change its contents. The same applies to the anti-collision identifier (UID).

ATS vs. ATR

Note that contactless smartcards (ISO/IEC 14443-4A) do not expose an ATR (answer-to-reset) during the activation sequence. Instead, they provide an ATS (in response to the selection procedure). PC/SC readers for contactless smartcards typically map parts of that ATS into an (emulated) ATR for compatibility.

Rooted devices

Even though Android does not provide an API, you might be able to modify values such as the ATS by modifying the NFC controller configuration files. See Editing Functionality of Host Card Emulation in Android and Host-based Card Emulation with Fixed Card ID