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Merchant & POS
With the introduction of chip cards into our lives, the terminal needs to verify the credit card before the transaction. So how is this verification performed? The value calculated and sent by the card is called ARQC (Application Request Cryptogram).
Online & Authorization
In EMV, data is stored in Tag-Length-Value (TLV) format, and it is carried between the card, the POS terminal, and the authorization system in this same format. This post lists every EMV Tag, its type, and its description.
EMV
The EXTERNAL AUTHENTICATE command asks the application inside the ICC whether it can verify the cryptogram, and the ICC returns the processing status. Below are the components of the External Authenticate command and what issuer authentication means.
Credit Card
CVR (Card Verification Results) refers to the results of checks performed on the card. In short, it can be described as keeping the card's transaction log. BYTE 1 Bit 8-7: 00 = The second GENERATE AC command returned an AAC cryptogram (decline)...
HCE
Generating a token from the card number is essential to the security of payments made with mobile devices. The level of tokenization used depends on the need and on how critical the token is. Static tokenization: the token is generated once and stored in a database.
Credit Card
iCVV stands for Integrated Circuit Card Verification Value. To prevent fraud, it is a CVV value generated similarly to the card's track data and stored on the card's chip. Visa uses the term iCVV; MasterCard and American Express use their own equivalents.
Online & Authorization
TLV is a data storage method used to speed up the parsing of data. For example, reading data from a card's chip at a POS and carrying it through authorization uses the TLV structure.
Credit Card
Card copying usually happens with magnetic stripe debit cards. As soon as you notice your card details have been copied, you can close the card, renew it or change its PIN.
ISO 8583
F55 - INTEGRATED CIRCUIT CARD (ICC) SYSTEM RELATED DATA: the field where EMV data is written on chip cards. It consists of components such as Position, Private Data Subelements, PDS Tag, PDS Length, and PDS Value...
ISO 8583
F23 - CARD SEQUENCE NUMBER: Information used to distinguish cards sharing the same card number. For example, the Card Sequence Number is incremented by 1 when a card is renewed. In an authorization transaction, if the F22 value is '05x'...
HCE
Token types vary depending on the verification method used in a transaction. In offline transactions, general checks are performed by the mobile app and card reader without any verification in the card system. In online transactions, token verification is sent to and verified by the issuer.
HCE
The token used in HCE transactions contains more than just a new number derived from the card number. It also includes single-use keys, an expiration date, RSA keys and certificates, transaction limits, and an Application Transaction Counter (ATC).