초록 ▼

An integrated circuit decoder for providing microcomputer users with access to several proprietary programs selected from a large group of such programs that have been distributed to users in cipher. The decoder chip can decipher a program if an enciphered key called a “permit code”is presented to t

An integrated circuit decoder for providing microcomputer users with access to several proprietary programs selected from a large group of such programs that have been distributed to users in cipher. The decoder chip can decipher a program if an enciphered key called a “permit code”is presented to the decoder chip. Permit codes are not interchangeable between decoders, are issued only to customers that have paid for use of a program product, and each code will work only with one program. As the program is being deciphered in a user\s microcomputer, the decoder chip places random errors into the program which make copies of the program malfunction in other microcomputers. The decoder chip keeps a table of addresses where it has placed errors and dynamically corrects the errors on the data bus whenever an error word is addressed during execution. Using such a decoder, thousands of individually priced proprietary software products can be delivered securely to prospective customers in advance of sales on laserdiscs, diskettes, TV-cables, and digital radio broadcasts.

대표청구항 ▼

A cryptographic apparatus for deterring unauthorized execution of computer programs of instructions stored in enciphered form as a plurality of portions of enciphered information, the apparatus comprising: means for deciphering an enciphered program key as a function of a secret chip key to produce

A cryptographic apparatus for deterring unauthorized execution of computer programs of instructions stored in enciphered form as a plurality of portions of enciphered information, the apparatus comprising: means for deciphering an enciphered program key as a function of a secret chip key to produce a deciphered program key corresponding to a selected program; means for deciphering portions of said enciphered information as a function of said deciphered program key to produce deciphered instructions in said selected program; table means for storing a plurality of digital addresses and a corresponding plurality of multiple-bit digital words; means for determining whether a memory address matches one of the digital addresses in said table means; means for reenciphering a plurality of said deciphered instructions or portions thereof to produce reenciphered instructions to be stored at memory locations specified by memory addresses, the reenciphering being performed on an instruction or portion thereof if said determining means determines that the memory address of the instruction matches one of the digital addresses in said table means, the reenciphering being a function of the digital word in said table means corresponding to the matching digital address; and means for redeciphering one of said reenciphered instructions whenever the instruction is fetched for execution from a memory location specified by a memory address matching one of the digital addresses in said table means, the redeciphering being performed as a function of the digital words in said table means corresponding to the digital address that matches the memory address of the instruction, thereby restoring reenciphered instructions to unenciphered form during execution of said selected program.