PINblock

PINblock is a security mechanism used in the payment card industry to protect the Personal Identification Number (PIN) entered by a cardholder during a transaction. The PIN is never transmitted in plaintext over a network. Instead, it is encrypted and formatted into a PINblock, which is then sent to the card issuer for verification. This process helps to prevent unauthorized access to the PIN and reduces the risk of fraud.

The PINblock is typically formatted according to the ANSI X9.8 standard, which specifies the structure and encryption method. The PIN is padded with random digits to a fixed length, usually 16 digits, and then encrypted using a symmetric key algorithm, such as Triple DES or AES. The resulting ciphertext is the PINblock, which is sent to the card issuer for verification.

The PINblock is used in various payment card systems, including EMV (Europay, MasterCard, and Visa) and magnetic stripe cards. It is an essential component of the PIN verification process, which helps to ensure that the cardholder is authorized to use the card. The use of PINblocks helps to protect the PIN and reduce the risk of fraud, making it an important security feature in the payment card industry.