The data address portions of a set of computer instructions are scrambled in accordance with a predetermined cipher key before the instructions are loaded into the instruction memory. The instructions with the scrambled data address portions are then loaded into the instruction memory at addresses corresponding to the original program sequence. The data involved in the program is loaded into a separate data memory at the addresses specified in the original unscrambled program. An unscrambler cir...

A hardware counter counts high rate, lower significant bits. A carry-borrow circuit responsive to the higher order bit position of the hardware counter includes cancel means responsive to successively received carry and borrow signals to cancel previously generated carries or borrows. Memory means in the carry-borrow circuit memorize the generation of the carry or borrow by the hardware counter. A programmed microprocessor, or the like, periodically senses the status of the carry-borrow circuit ...

A digital processor capable of responding to a sync instruction for high-speed synchronization of hardware and software is provided. The sync instruction places the procesor in a stopped state and lets the processor start up again only upon receipt of an interrupt. If the interrupt is disabled by being masked, the stopped state is simply cleared and the sequencing of instructions continues without vectoring to the interrupt service routine. However if the interrupt is not disabled, the processor...

In a microprocessor system, data stored in a protected memory (12) within the same housing as the microprocessor (10) are secured by enabling access to the contents of the memory in response to an instruction only if the instruction was previously fetched from the memory (12). Protection circuitry (14) comprises a decoder (22, 24) responsive to the output of a status register in the microprocessor to operate a status signal when the microprocessor is in an instruction fetch machine cycle. The st...

Methods and apparatus are disclosed for inhibiting the unauthorized copying of ROM-resident computer software or the like, for example, the audio-visual display of an electronic video game. A protection circuit including encryption/decryption means is coupled between the microprocessor and the ROM-memory and is operable in a first mode to properly encrypt/decrypt the program information according to a first algorithm and in a second mode to prevent proper encryption/decryption. The address-data ...

A protection system for controlling the operation of a digital computer as to a particular program wherein a program "lock" interfaces with the computer and authorizes the operation in response only to a selected relation between a number in the program, a number in the lock, and a third number, a "key", supplied to the lock and which bears a selected relation to both the program number and lock number.

An address control system for software simulation in a virtual machine system having a virtual storage function. When a simulator program is simulating an instruction of a program to be simulated, an address translation of an operand address in the program to be simulated is achieved using a translation lookaside buffer, thereby greatly reducing the overhead for the address translation during the simulator program execution.

The disclosure relates to a security system for computer software. A plug-in circuit accompanies each legitimately purchased softward package. The software includes a communication system to decode signals generated by the plug-in circuit. Where the appropriate signal is sensed the program is executed. If the proper code is not sensed the program shuts down.

A central station distributes software by telephone. The central station accepts credit card information, transmits an acceptance code to a caller and then terminates the call. After verifying the credit card information, the station calls the purchaser back and continues with the transaction only after receiving the acceptance code. The central station then transmits a Control Transfer Program and Initialization Program to the purchaser, and the purchaser executes the Initialization Program to ...

A method of protecting machine readable signals recorded on magnetic recording media from unauthorized duplication and use. The signals to be protected are recorded on an authorized magnetic recording medium having a relatively high coercivity. An attempt is made by the computer to alter predetermined validating signals on a recording medium presented for use in the computer. The computer is disabled from further using the signals recorded on the recording medium if the validating signals cannot...