如何存储和验证PIN码

Question

I am developing a scratch-card voucher pin application

1. The 12 digit pin will be generated by pseudo-random tool
2. The pin (and a serialno) is tored in the database for authentication
3. User type in the pin to use a service, and the pin is checked against the database for verification by scanning through the Pin Column
4. The pin should also be decoded (in rare cases)

Problem If the pin is encrypted, it will be difficult query the database for the verification. Since the search is based on pin. How do i store the pin code so that

1. It can be unique, and matched during verification

Answer 1

Just encrypt the pin and store it. When the user enters the pin for verification, encrypt it also and compare the encrypted stored pin with the encrypted user-entered pin. If you need to decode pin in rare cases, use a decodable encryption. I would recommend not doing so and forcing the user to update to a new pin if he loses or forgets the old one.