Security is first of all strengthened during the control of the Personal Identification Number
Security is first of all strengthened during the control of the Personal Identification Number (PIN code).
Security is then strengthened in case of loss or theft. Indeed, the card is automatically disabled when the user keys in 3 wrong PIN codes in a row whatever the transaction is. Unscrupulous persons cannot thus key in all possible values until they find the correct one.
At last, security is strengthened with the fact that the PIN code is stored in the chip. Indeed, only the manufacturer of the chip can read the PIN code if needed. Nobody else can do that.