Methods and apparatuses for key generation, encryption and decryption in broadcast encryption. A public parameter and a primary key based on a first random number are generated. For each of leaf nodes in a binary tree, a right key set of the leaf node is calculated, the right key set including a right key of the leaf node and right keys of right brother nodes for all the nodes on a path from a root node to the leaf node. A left key set of the leaf node is calculated, the left key set including a left key of the leaf node and left keys of left brother nodes for all the nodes on the path. The sum of the second and third random numbers equals to the first random number. The second random number is different for different subscribers.