A "return on investment" digital database usage metering, billing, and security system includes a hardware device which is plugged into a computer system bus (or into a serial or other functionally adequate connector) and a software program system resident in the hardware device. One or more databases are encrypted and stored on a non-volatile mass storage device (e.g., an optical disk). A tamper-proof decrypting device and associated controller decrypts selected portions of the stored database and measures the quantity of information which is decrypted. This measured quantity information is communicated to a remote centralized billing facility and used to charge the user a fee based on database usage. A system may include a "self-destruct" feature which .disables system operation upon occurrence of a predetermined event unless the user implements an "antidote"--instructions for implementing the antidote being given to him by the database owner only if the user pays his bill. Absolute database security and billing based on database usage are thus provided in a system environment wherein all database access tasks are performed at the user's site. Moreover, a free market competitive environment is supported because literary property royalties can be calculated based on actual data use.