Security protocols for hybrid peer-to-peer file sharing networks

A method implemented at a provider peer device in a peer-to-peer network comprising a receiver peer device and multiple provider peer devices, wherein the multiple provider peer devices comprise the provider peer device, the method comprising:

• a) receiving by the provider peer device from a receiver peer device a ticket comprising an authorization by the server for the receiver peer device to obtain a data object O from any one of the multiple provider peer devices;
• wherein the ticket is digitally signed by the server and comprises a receiver identifier associated with the receiver peer device and an object identifier associated with the data object O;
• b) verifying by the provider peer device a digital signature of the ticket, whereby the provider peer device may verify that the ticket originated from the server;
• c) receiving by the provider peer device from the receiver peer device a request for a block of the data object O,
• wherein the request comprises a block sequence number corresponding to the block;
• d) sending by the provider peer device to the receiver peer device the block of the data object O, wherein the block is encrypted by the provider peer device using a block key uniquely associated with the block;
• e) receiving by the provider peer device from the receiver peer device an acknowledgement of receipt of the block,
• wherein the acknowledgement is digitally signed by the receiver peer device to produce a digital signature,
• wherein the acknowledgement comprises a digest of the block and a provider identifier;
• f) verifying by the provider peer device the digital signature, whereby the provider peer device may verify that the acknowledgement originated from the receiver peer device;
• g) verifying by the provider peer device the digest, whereby the provider peer may verify that the block of the data object O was correctly received by the receiver peer device;
• h) sending by the provider peer device to the receiver peer device, in response to the acknowledgement, the block key, wherein the block key is digitally signed by the provider peer device;
• and
• i) sending by the provider peer device to a server the acknowledgement, whereby the server may give credit to the provider peer device for providing the block to the receiver peer device.

A method implemented at a server in a peer-to-peer network comprising the server, a receiver peer device, and multiple provider peer devices comprising a provider peer device, the method comprising:

• a) receiving by the server from the receiver peer device a request for authorization to obtain a data object O;
• b) generating by the server a ticket authorizing the receiver peer device to obtain the data object O from any one of the multiple provider peer devices,
• wherein the ticket comprises a receiver identifier associated with the receiver peer device and an object identifier associated with the data object O,
• c) digitally signing by the server the ticket;
• d) sending by the server the ticket to the receiver peer device, whereby the receiver peer device may use the ticket to obtain the data object O from the provider peer device by providing the ticket to the provider peer device;
• e) if the server receives a request from the receiver peer device for a block key for a block of the data object O, calculating by the server the block key and sending by the server the block key to the receiver peer device;
• f) receiving by the server from the provider peer device a copy of an acknowledgement sent from the receiver peer device to the provider peer device acknowledging receipt by the receiver peer device of a portion of the data object O transmitted by the provider peer device,
• wherein the acknowledgement is digitally signed by the receiver peer device to produce a digital signature of the acknowledgement,
• wherein the acknowledgement comprises a provider identifier and a digest of at least one block of the data object O that was transmitted from the provider peer device to the receiver peer device;
• g) verifying by the server the digital signature of the acknowledgement, whereby the server may verify that the acknowledgement originated from the receiver,
• h) verifying by the server the digest, whereby the server may verify that the at least one block of the data object O was correctly received by the receiver peer device;
• i) giving by the server credit to the provider peer device using the acknowledgement as proof-of-service if the digital signature of the acknowledgement is verified and the digest contained in the acknowledgement is verified.