Host Card Emulation (HCE) allows Android NFC devices to function like smart cards and emulate contactless card payments without a secure element. HCE stores card data in the device's memory rather than a secure element, enabling multiple payment wallets on a device. Implementing HCE requires declaring an NFC service in the manifest, registering Application IDs (AIDs) for card emulation, and processing Application Protocol Data Unit (APDU) commands from NFC readers in the onCommandApdu() method of a HostApduService. HCE services must also handle AID conflicts if multiple services use the same AID and ensure security through permissions and Android application sandboxing.

1. Host Card Emulation (HCE)

2. NFC

3. NFC APPS

4. Card Emulation with a Secure Element

5. Host-based Card Emulation
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Host Card What?
Host Card Why?
Implementing an HCE
Service
Host Card Security

6. Host Card What?
• Where data is routed ?
• Support for many different protocols
• Android NFC devices functioning as readers
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( IsoDep class).
HCE services

7. Host Card Why?
• No more complex SE cards.
• Multiple NFC payment wallets can be on the
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phone
No worrying about SE storage size.
No need to pay the Carrier for Over-the-air SE
provisioning and lifecycle management.
Enabling any wallet to use it to communicate to
a PoS

8. Implementing an HCE Service

9. Implementing an HCE Service
• Service selection
• AID groups and categories
• Service implementation
• Service manifest declaration and AID
registration

10. Service
Selection

11. Service selection
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ISO/IEC 7816-4 specification
Application ID (AID).
Length between 5 and 16 bytes
AID well-known and publicly registered
What if you want to deploy new reader infrastructure for
your own application ?

12. AID Groups
• AID group is a list of AIDs that should be
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considered as belonging together by the OS
HCE service may need to register multiple AIDs
to implement a certain application
Android guarantees one of the following
o All AIDs in the group are routed to this HCE service
o No AIDs in the group are routed to this HCE service

13. AID groups and categories
• Each AID group can be associated with a
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category
avoid mentioning AIDs in any user-facing
parts of your application.
Android 4.4 supports two categories:
o CATEGORY_PAYMENT
o CATEGORY_OTHER

14. Checking for HCE support
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Your application can check whether a device supports
HCE by checking for the
FEATURE_NFC_HOST_CARD_EMULATION feature.

15. Service implementation
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The first step is therefore to extend HostApduService.
HostApduService declares two abstract methods that
need to be overridden and implemented

16. Service implementation (2)
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processCommandApdu() is called whenever a NFC
reader sends an Application Protocol Data Unit (APDU)
to your service
"SELECT AID" APDU.
processCommandApdu() run on the main thread.
When Android will stop forwarding new APDUs from the
reader to your service ?
o The NFC reader sends another "SELECT AID" APDU, which the OS
resolves to a different service
o The NFC link between the NFC reader and your device is broke.
In both of these cases,onDeactivated() implementation is called

17. Android Protocol Data Unit (APDU)
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APDUs are the application-level packets being
exchanged between the NFC reader and your HCE
service.
APDU is a half-duplex.
Android’s HCE implementation only supports a single
logical channel.

18. Android Protocol Data Unit (APDU) (2)

19. Manifest declaration and AID registration

20. Manifest declaration and AID registration (2)

21. Screen Off and Lock-screen Behavior

22. AID Conflict Resolution
• The same AID can be registered by more
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than one service.
Checking if your service is the default

23. Secure element AID registration

24. Secure element AID registration (2)

25. Coexistence with Secure Element Cards

26. HCE and Security
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BIND_NFC_SERVICE
system permission.
Android Application
Sandbox,

27. HEADER

28. Ahmed Fathallah
Junior android developer
linkedin.com/in/ahmedfathallah/
ahmedfathalla02@gmail.com