Information processing apparatus (100) ensures confidentiality of encryption and reduces overhead associated with processing not directly related to the encryption. The information processing apparatus (100) includes: application program (A158) that includes an instruction for encryption which uses a key; tampering detection unit (135x) that detects tampering of the program; CPU (141) that operates according to instructions and outputs a direction for encryption upon detecting the instruction for encryption; data encryption/decryption function unit (160) that controls switching to the protective mode according to the direction; and protected data operation unit (155) that stores a key in correspondence with the program, outputs the key in the protective mode, and controls switching to the normal mode, and the data encryption/decryption function unit (160) executes the encryption in the normal mode using the received key.