DIGITALLY WRITTEN WORK PROTECTING SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a digitally written work protecting system which prevents illegal writing of a written work obtained from outside into a recording medium and illegal reproducing of the written work recorded in the recording medium. SOLUTION: The medium characteristic key storing part 220 of a memory card 200 stores a characteristic key Ki; a conversion part 230 generates a ciphered characteristic key Ji from the key Ki; the random number generating part 331 of a memory card writer 300 generates a random number R1; a ciphering part 252 generates a ciphered random number S1 from the number R1; a decoding part 333 generates a random number R'1 from the number S1, a mutual authentication control part 334 compares the number R'1 with the number R1 and authenticates the card 200 to be legal at the time of coincidence; when the memory card and an access device are authenticated to be legal to each other, the access device ciphers or deciphers the written work by using the decoded characteristic key.