ATC banking refers to the Application Transaction Counter (ATC), which is a crucial security feature in chip cards (EMV cards). The ATC is a counter maintained by the chip card itself, incrementing with each transaction. Think of it as a transaction number embedded in the card's chip.
Here's a breakdown:
- Application Transaction Counter (ATC): This is the sequential transaction number. The card's chip updates this counter with every use.
- Security: The ATC's primary role is to help detect fraudulent activities.
- How it Works: When a transaction occurs, the terminal reads the ATC from the card. The issuer (the bank) also keeps track of the expected ATC for that card.
- Fraud Detection:
- Duplicate ATC: If the issuer receives the same ATC twice, it could indicate that someone is trying to replay a transaction.
- Decreased ATC: A decrease in the ATC value suggests that the card's data has been tampered with or that a fraudulent copy of the card is being used.
- Large Jump in ATC: A significant jump in the ATC value, beyond what's reasonably expected, may also signal fraudulent activity. This could mean someone has somehow manipulated the card to artificially increase the counter.
In essence, the ATC provides a transaction history reference that helps the issuer verify the legitimacy of transactions and identify potentially fraudulent activities. The use of an incrementing counter that must match the issuer's record of transactions is a security measure to prevent replay attacks and other forms of fraud.
