| 摘要 |
<P>PROBLEM TO BE SOLVED: To enhance the encryption intensity of a content without changing an encryption algorithm. <P>SOLUTION: In a host 2, when the content is transferred to a memory card 3 from the host 2, an encryption and decryption module 4 encrypts the content by use of a common key Kc, a 4-bit conversion circuit 5 inputs the encrypted content in the bit order to a substitution module 7, and an encryption module 6 calculates a substitution key Kp. The substitution module 7 selects one of 4! substitutions based on the substitution key Kp to execute 4-bit substitution, and transmits the result to the memory card 3 while assigning it to data lines DAT0-DAT3. In the memory card 3, a substitution module 9 performs 4-bit substitution with the substitution key Kp calculated by the encryption module 9. A 4-bit conversion circuit 10 inversely transforms 4-bit data inputted from the substitution module 9 and outputs the result to an encryption and decryption module 11, which then decrypts the encrypted content by use of the common key Kc. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
