I am trying to generate AC manually, I have a tool to generate AC but I want to generate it by my own to understand the algorithm for the same.
My calculation is fine for Discover card but it is failing for MasterCard. As per my understanding, data used to generate AC is depend on Tag 8C - CDOL1 which we provide to card with Gen AC command + AIP + ATC.
AIP and ATC - accessed internally by ICC.
Data used to generate AC is:-
data part of Gen AC command + value of tag 82 + value of tag 9f36 + 80 + optional 00 to make it multiple of 8.
this is my logic ,it might be I am using wrong data to calculate A.C that's why getting different result from my test tool.
Terminal Supplied Data
Amount, Authorised - 000000000201
Amount, Other - 000000000000
Terminal Country Code - 0826 - United Kingdom
Terminal Verification Results - 00 00 00 00 00
Transaction Currency Code - 0826 - Pound Sterling
Transaction Date - 15 04 28
Transaction Type - 00 - Goods and Services
Unpredictable Number - 30 90 1B 6A
Terminal Type - 23 - Attended, offline only. Operated by Merchant
Data Authentication Code - 00 00
ICC Dynamic Number - 1E AB C1 26 F8 54 99 76
CVM Results - 00 00 00
Gen AC Using CDOL1 80 AE 40 00 2B 0000000002010000000000000826000000000008261504280030901B6A2300001EABC126F8549976000000 this command is returning 9F26. data i used for calcatation is:-
0000000002010000000000000826000000000008261504280030901B6A2300001EABC126F85499760000003800000180 [ data is multiple of 8]
Where 3800 is AIP 0001 is ATC and 80 for Padding [ Padding method 2 EMV] This is my logic, Is any body tell me where I should focus more to generate same AC as my tool generated.