How can I fool my EMV contactless card to do an offline contactless transaction by using ACR122U NFC reader and PyApdu tool?

Question

I already successfully done three of the five APDU commands-Responses which are done between the ACR122 NFC reader (which act as a POS) and an EMV Visa Debit Contactless card as foolwing. 1- List Available NFC Applications C-APDU:00 A4 04 00 0E 32 50 41 59 2E 53 59 53 2E 44 44 46 30 31 0E R-APDU:6F 47 84 0E 32 50 41 59 2E 53 59 53 2E 44 90 00 2- Select Application (AID) C-APDU:00 A4 04 00 07 A0 00 00 00 03 10 10 0E R-APDU:6F 56 84 07 A0 00 00 00 03 10 10 A5 4B 50 90 00 3-Get Processing Options (GPO) C-APDU:80 A8 00 00 23 83 21 F6 20 C0 00 00 00 00 00 00 01 00 00 00 00 00 00 08 26 00 00 00 00 00 08 26 17 10 31 00 71 17 0F 68 23 R-APDU:77 81 D1 82 02 20 00 94 04 10 02 05 00 57 13 XX XX XX XX XX XX XX XX D2 01 12 01 00 93 60 00 00 00 1F 5F 90 00 now. how can I fool my card to do offline contactless transaction with my ACR122 reader and do a genuine transaction?

Answer 1

The decision as to whether the card has to approve/decline a transaction offline, or send online is decided at card. the terminal can ask the card to give a TC in GEN AC, however the card not necessarily should give back a TC to approve the transaction offline. based on the risk management done at card, it can be ARQC or AAC. For a card where floor limit is enabled, adjust the transaction to have no unexpected bits turned on against card and terminal action codes, it should give you an approval in ideal case.