Data processing apparatus with software protecting functions

A data processing apparatus with software protecting functions based on data encryption and decryption, comprising:

• an encryption key generation circuit for generating an encryption key depending on an attribute of data including instructions to be encrypted;
• a decryption key generation circuit for generating a decryption key depending on an attribute of encrypted data;
• an encryption circuit for encrypting data to be encrypted by use of said encryption key generated by said encryption key generation circuit;
• a memory for storing encrypted data from said encryption circuit;
• a decryption circuit for decrypting said encrypted data in said memory by use of said decryption key generated by said decryption key generation circuit;
• an MPU connected directly to said decryption circuit so as to process data decrypted by said decryption circuit in accordance with instructions included in the decrypted data;
• and
• a control circuit for outputting processed data from said processing circuit directly to said encryption circuit as data to be encrypted.

A data processing apparatus with software protecting functions based on data encryption and decryption, comprising:

• key supply means for supplying a plurality of keys used for encryption and decryption;
• algorithm supply means for supplying a plurality of pieces of algorithm information expressing algorithms for encryption and decryption;
• encryption-decryption method selection means for selecting an encryption key and encryption algorithm information respectively from among said plurality of keys and said plurality of pieces of algorithm information supplied for encryption, and selecting a decryption key and decryption algorithm information respectively from among said plurality of keys and said plurality of pieces of algorithm information supplied for decryption;
• encryption means for encrypting data to be encrypted by use of the encryption key and encryption algorithm information selected by said encryption-decryption method selection means;
• storage means for storing encrypted data from said encryption means;
• decryption means for decrypting said encrypted data in said storage means by use of the decryption key and decryption algorithm information selected by said encryption-decryption method selection means;
• processing means connected directly to said decryption means so as to process data decrypted by said decryption means in accordance with instructions included in the decrypted data;
• and
• control means for outputting processed data from said processing means directly to said encryption means as data to be encrypted.