A software duplication prevention system comprising: a terminal that includes a receiver for data transmitted from a post and basic software and application program; and a plurality of posts that includes a transmitter transmitting the data to the terminal, wherein: the data transmitted from the post is transmitted as a second encrypted code encrypted with a second encryption key; the terminal includes a first decryption part decrypting a first encrypted code that is included in the application program and is encrypted with a first encryption key, a first decryption key corresponding to the first encryption key and being included in the basic software, and a second decryption part decrypting the second encrypted code, which is received; the basic software is configured not to operate unless being notified of the first encrypted code from the application program; the second encrypted code corresponding to the data includes an ID which is information unique to each post, the ID being capable of identifying each post of the plurality of posts; and the terminal executes the basic software to decrypt the first encrypted code with the first decryption key and to acquire a second decryption key corresponding to the second encryption key, and decrypts the second encrypted code with the second decryption key. a terminal that includes a receiver for data transmitted from a post and basic software and application program; and a plurality of posts that includes a transmitter transmitting the data to the terminal, wherein: the data transmitted from the post is transmitted as a second encrypted code encrypted with a second encryption key; the terminal includes a first decryption part decrypting a first encrypted code that is included in the application program and is encrypted with a first encryption key, a first decryption key corresponding to the first encryption key and being included in the basic software, and a second decryption part decrypting the second encrypted code, which is received; the basic software is configured not to operate unless being notified of the first encrypted code from the application program; the second encrypted code corresponding to the data includes an ID which is information unique to each post, the ID being capable of identifying each post of the plurality of posts; and the terminal executes the basic software to decrypt the first encrypted code with the first decryption key and to acquire a second decryption key corresponding to the second encryption key, and decrypts the second encrypted code with the second decryption key. the data transmitted from the post is transmitted as a second encrypted code encrypted with a second encryption key; the terminal includes a first decryption part decrypting a first encrypted code that is included in the application program and is encrypted with a first encryption key, a first decryption key corresponding to the first encryption key and being included in the basic software, and a second decryption part decrypting the second encrypted code, which is received; a first decryption part decrypting a first encrypted code that is included in the application program and is encrypted with a first encryption key, a first decryption key corresponding to the first encryption key and being included in the basic software, and a second decryption part decrypting the second encrypted code, which is received; the basic software is configured not to operate unless being notified of the first encrypted code from the application program; the second encrypted code corresponding to the data includes an ID which is information unique to each post, the ID being capable of identifying each post of the plurality of posts; and the terminal executes the basic software to decrypt the first encrypted code with the first decryption key and to acquire a second decryption key corresponding to the second encryption key, and decrypts the second encrypted code with the second decryption key.