In P2P networks, users share legal media contents with each
other but it then evokes another intellectual property management
issues that the system has to guarantee legal video
consumption. The DRM is adopted for the P2P multicast system
to provide secured transmission and manage user priority.
In addition to provide secured content delivery, the DRM
has to act as a key generator, e.g., common scrambling algorithm
(CSA). It transmits a cipher key to the media server to
provide real-time encrypted streaming with acceptable delay.
The CSA is used to encrypt bitstreams of live meta-data in the
digital video broadcasting (DVB) system. The control words
are used to generate CSA keys, which are provided by a conditional
access mechanism that utilizes the DRM encrypted
control messages embedded in the transport packet.
The Open IPTV Forum adopts Marlin-based Content
Protection and Service Protection Specification (OIPF-CSP)
standard. As shown in Fig. 4, it comprises four function
modules. The Security Management Center (SMC) manages
usage permission. The Broadcaster is responsible for content
encryption. An IPMP terminal is the interface for user
authentication and content decryption, and the Peer Management
Center (PMC) monitors peer connection efficacy to
maintain the QoS. The content protection mechanism is carried
out by the following steps: (1) Before joining the P2PIPTV,
an IPMP terminal requests SMC to access the service
through a web browser; (2) After the user connecting to the
SMC, the DRM sends RSA public key to the IPMP terminal
to encrypt user profiles; (3) The encrypted user profile is
protected by RSA which is provided by SMC and transmitted
to the DRM for user identification; (4) After performing
authentication with database, the DRM transmits Electronic
Program Guides (EPG) to the user; (5) The DRM informs the
PMC to confirm the connection policy of the new peer; (6)
The PMC notifies both Broadcaster and IPMP terminal about
the connection policy; (7) The Broadcaster and the IPMP terminal
send public keys to SMC to encrypt CSA keys for descrambling;
(8) The SMC sends encrypted CSA keys to both
Broadcaster and IPMP terminal to scramble and descramble
contents, respectively. The encrypted CSA key can be decrypted
and retrieved using their own private keys; (9) The
Broadcaster streaming scrambled data to IPMP terminal; (10)
The IPMP Terminal descrambles the streaming using CSA
key and displays the contents; (11) The current peer may receive
other CSA keys for content scrambling if PMC notifies
the user. This security control mechanism can also be operated
between a parent peer and a child peer, which act as a
broadcaster and an IPMP terminal, respectively. It’s carried
out that each inter-peer connection would be assigned a new
encryption/description key and secured by imposing this content
protection mechanism and this local inter-peer security
transmission eventually guarantees the entire P2P-IPTV system
secured. Detailed control steps can be demonstrated with
the aides of Fig. 5. This security issue suggests the adoption
of tree-based broadcasting, instead of mesh-based.