A method comprising: performing a login process at a server for a first user, wherein an identifier is assigned to the first user; performing a process for generating a digital object based on data entered by the first user at the server, wherein the data includes an indication of the amount of a resource, and wherein the digital object includes the identifier and the indication of the amount of the resource and a duration of time; encrypting the digital object and transmitting the digital object to a second user, wherein a destination address of the second user is indicated by the first user of the server; performing a registration or login process via the server for the second user in response to execution of the digital object by the second user; decrypting the digital object and reading the identifier of the first user and the indication of the amount of the resource and the duration of time; reducing an indication of the amount of the resource for the first user in a data structure by the indicated amount of the resource, and increasing an indication of the amount of the resource for the second user in the data structure by the indicated amount of the resource; storing the duration of time for the first user and the amount of the resource in the data structure, and storing the duration of time for the second user and the amount of the resource in the data structure; increasing the indication of the amount of the resource for the first user in the data structure after expiration of the duration of time for the first user, and reducing the indication of the amount of the resource for the second user in the data structure after expiration of the duration of time for the second user; wherein the resource comprises storage space on the server and/or accesses to data on the server. performing a login process at a server for a first user, wherein an identifier is assigned to the first user; performing a process for generating a digital object based on data entered by the first user at the server, wherein the data includes an indication of the amount of a resource, and wherein the digital object includes the identifier and the indication of the amount of the resource and a duration of time; encrypting the digital object and transmitting the digital object to a second user, wherein a destination address of the second user is indicated by the first user of the server; performing a registration or login process via the server for the second user in response to execution of the digital object by the second user; decrypting the digital object and reading the identifier of the first user and the indication of the amount of the resource and the duration of time; reducing an indication of the amount of the resource for the first user in a data structure by the indicated amount of the resource, and increasing an indication of the amount of the resource for the second user in the data structure by the indicated amount of the resource; storing the duration of time for the first user and the amount of the resource in the data structure, and storing the duration of time for the second user and the amount of the resource in the data structure; increasing the indication of the amount of the resource for the first user in the data structure after expiration of the duration of time for the first user, and reducing the indication of the amount of the resource for the second user in the data structure after expiration of the duration of time for the second user; wherein the resource comprises storage space on the server and/or accesses to data on the server. <EOS>