Circuit for preventing copy of memory data without permission

PURPOSE: To prevent copy of data without permission and to maintain the security by outputting data of different addresses from those of concerned data when copy of data without permission is inhibited. CONSTITUTION: In the state where ciphered data stored in a ciphering data storage section 10 are applied to a data conversion section 10 by a switching section 20, when a party who is not permitted to copy, designates concerned addressed AD1-ADm of the data storage section 10 and inputs them to the data conversion section 30, the data are converted by an exclusive OR gate of the data conversion section 30 and applies respectively to an X-address buffer/decoder 50 and a Y-address buffer/decoder 60. Data different from data desired by copied by the party whose copying is not permitted are outputted from the data storage section 10. On the other hang, input data not ciphered are given to the data storage section 10 through the X-address buffer/decoder 50 and the Y-address buffer/decoder 60 and outputted via a sense amplifier 80 and a data output buffer/driver 90.