A cost-effective system that provides for the efficient protection of transmitted non-public attribute information may be used, for example, to control access to a secure area. Encryption of the attribute information may be performed using symmetric encryption techniques, such as XOR and/or stream cipher encryption. A centralized database that stores and transmits the encrypted attribute information may generate the encryption/decryption key based on selected information bytes, for example, as taken from a card inserted into a handheld device used at the secure area. The selected information to generate the encryption key stream may be varied on a periodic basis by the centralized database. Information as to which selected bytes are to be used for a particular access authorization request may be transmitted to the handheld unit or may be input through action of a user of the handheld unit, for example by entry of a PIN code.