Information processing apparatus and method and recording medium

An application program that was encrypted by using a predetermined secret key is input to an input section that is a part of a program execution system, and encrypted sentences as the encrypted application program are supplied to a decoding section as they are. The decoding section is supplied not only with the encrypted sentences from the input section but also with a publicized key corresponding to a secret key that was used in generating the encrypted sentences. The decoding section decodes the encrypted sentences by using the publicized key and supplies Java byte codes as a decoding result to a Java virtual machine. The Java virtual machine interprets and executes the Java byte codes that are supplied from the decoding section.