PURPOSE: To avoid the unreasonable accesses to programs and data by using a cipher processing function to cipher the information showing the recording positions of programs and data.

CONSTITUTION: When an uncontracted program product number N and a ciphering key K are supplied to an information processor 10, an access managing part 40 reads a memory address out of a memory address part 32 in response to the product number N of a program product number 31 of a memory managing table part 30. Then said memory address is ciphered by a cipher processing part 41 via the key K. An access is given again to the product number N of the part 31 and the corresponding memory address of the part 32 is rewritten into a ciphered one. Thus the position shown by a memory address is different from an actual position. As a result, the access are impossible to programs or data.