The possibility to visualize a file offer during an on-line tender means that another supplier could modify and adjust his own offer.
The solution is Telematic Sealed Envelope. It consists on a temporal sequence of operations that guarantees telematic offers’ inviolability and ensures transparency and absolute impartiality.
Digital signature and timestamp are essential requirements. They guarantee the impossibility of modifying the file. In fact any kind of intervention will immediately lead to the timestamp forfeiture. But they do not guarantee not visibility of the content if system logs are held by service operator.
Similarly, an identification code, as hash, can be assigned to the offer file in order to guarantee that the file will not be replaced but it does not guarantee not visibility of the offer.
The only possible solution is temporal subdivision between the sending of the offers or their identification codes and the possibility to read them, in order to guarantee the correspondence between identification codes that have been sent and collected files.