A data transmission system comprising: a storage site information transmitter that transmits storage site information representing a storage site of data to be encrypted to a certain destination of a person to which data is to be released, the certain destination being that of an unregistered user; an access acceptor that accepts an access accompanied with the storage site information; and a password information transmitter that transmits password information, in a case where the access accompanied with the storage site information is accepted, to the destination associated with the data, wherein the password information serves as a decryption key for decrypting the data to be encrypted after the data has been encrypted, wherein the timing at which the password information for the data is transmitted comes after a certain period has elapsed since the timing at which the storage site information for the data is transmitted and wherein the timing at which the password information is transmitted is just after the timing at which the person to which data is to be released actually accesses the storage site of the data, so that the person to which data is to be released can specify the password information that is necessary to decrypt the encrypted data; the data transmission system further comprising: a password information generator that newly generates the password information in a case where the access accompanied with the storage site information is accepted, and an encrypted data generator that, in a case where the access accompanied with the storage site information is accepted and the password information generator newly generates the password information, generates the encrypted data that is able to be decrypted by using the newly generated password information as a decryption key, wherein the password information transmitter transmits the password information newly generated by the password information generator to the destination. a storage site information transmitter that transmits storage site information representing a storage site of data to be encrypted to a certain destination of a person to which data is to be released, the certain destination being that of an unregistered user; an access acceptor that accepts an access accompanied with the storage site information; and a password information transmitter that transmits password information, in a case where the access accompanied with the storage site information is accepted, to the destination associated with the data, wherein the password information serves as a decryption key for decrypting the data to be encrypted after the data has been encrypted, wherein the timing at which the password information for the data is transmitted comes after a certain period has elapsed since the timing at which the storage site information for the data is transmitted and wherein the timing at which the password information is transmitted is just after the timing at which the person to which data is to be released actually accesses the storage site of the data, so that the person to which data is to be released can specify the password information that is necessary to decrypt the encrypted data; the data transmission system further comprising: a password information generator that newly generates the password information in a case where the access accompanied with the storage site information is accepted, and an encrypted data generator that, in a case where the access accompanied with the storage site information is accepted and the password information generator newly generates the password information, generates the encrypted data that is able to be decrypted by using the newly generated password information as a decryption key, wherein the password information transmitter transmits the password information newly generated by the password information generator to the destination. a password information generator that newly generates the password information in a case where the access accompanied with the storage site information is accepted, and an encrypted data generator that, in a case where the access accompanied with the storage site information is accepted and the password information generator newly generates the password information, generates the encrypted data that is able to be decrypted by using the newly generated password information as a decryption key, wherein the password information transmitter transmits the password information newly generated by the password information generator to the destination.