A system for disabling an unauthorized person includes an encryption device (400) and a decryption device (500). The encryption device (400) stores distribution member set data, a random number, and a public key, the distribution member set data being information on members who are permitted to decrypt a cyphertext, and generates and distributes, when a shared key is input, an error-containing cyphertext which is a cyphertext containing the shared key, the distribution member set data, and error information different for each of the members, and an error correction cyphertext which is a cyphertext of the error information. The decryption device (500) is connected to the encryption device, stores the public key and a secret key corresponding to the own device, determines, upon reception of the error-containing cyphertext and the error correction cyphertext from the encryption device, whether the own device is included in the distribution member set data, decrypts, if the own device is included in the distribution member set data, the error-containing cyphertext and the error correction cyphertext with the public key and the secret key, and removes the error information from the decrypted error-containing cyphertext to output the shared key.