(PIN) A unique identifier used together with a personal identification device (PID).
Personal identification numbers (PINs) are used to protect the security of PIDs by providing added proof that the person trying to use the PID is in fact the authorized owner. PINs are known only to the person who owns the PID and should never be divulged to anyone. PINs are typically numbers with four or more digits; the length of the number often is a characteristic of the type of PID being used. PINs help ensure that an individual’s personally identifiable information (PII) stored on the PID remains private and does not fall into the hands of unauthorized parties.