Patent ID: 7848525

Claim:
A hybrid broadcast encryption method comprising: setting initialization values, generating a node secret using the initialization values; generating a private secret using the node secret; sending the node secret and the private secret; generating a broadcast message based on a revoked group; encrypting a session key using a key encryption key (KEK) which is allocated to every user group and the broadcast message; and broadcasting to every user the encrypted session key and the broadcast message, wherein the broadcasting includes: generating plural random numbers w(1,i) and w(2,i) for every user group; calculating P(i,R) and P(i,j,R) with respect to the revoked group R by using an equation; generating broadcast messages Ō(t,i) and e(i,j) based on the P(i,R) and the P(i,j,R); and broadcasting the encrypted session key and the broadcast messages Ō(t,i) and e(i,j), wherein the w(1,i) and w(2,i) are random numbers, P(i,R) and P(i,j,R) are predetermined equation, Ō(t,i) and e(i,j) are broadcast messages sent from a server.