Distribution of multicast data to users

A method of multicasting a file, comprising:

• encrypting the file using one or more keys;
• transmitting the encrypted file to a plurality of receivers in a multicast transmission;
• providing at least one of the plurality of receivers with one or more decryption keys required for decrypting the transmitted encrypted file, after the file was transmitted;
• and
• providing at least one of the receivers with at least one decryption key for the encrypted file, before transmitting the encrypted file,
• wherein the at least one of the receivers provided with the decryption keys before transmitting the encrypted file are selected at least partially responsive to previous behavior of the receivers.

A method of transmitting multicast data, comprising:

• providing a data file for transmission;
• estimating one or more transmission parameter values required to achieve, on the average, a reception rate which allows less than 100% of the receivers to which the multicast data is directed to reconstruct the data file from the multicast transmission;
• transmitting the multicast data representing the data file on a multicast channel, using the one or more estimated parameter values;
• and
• providing at least supplementary portions of the data to receivers that were not able to reconstruct the data file in its entirety from the multicast data transmitted on the multicast channel.

A method of transmitting multicast data in a cellular network, comprising:

• providing data for multicast transmission to a plurality of base stations having different bandwidth amounts for multicast transmission, at a same rate;
• dropping data by one or more of the base stations, as required, so that the data can be transmitted by each of the base stations on its respective allocated bandwidth for multicast transmission;
• and
• transmitting the non-dropped data such that the data is transmitted by all the base stations substantially synchronously.