A method of protecting digital contents includes: requesting an external device or service to perform a part of a process of decrypting encrypted contents which correspond to a leaf node among a plurality of leaf nodes in a tree used in a revocation mechanism according to whether the leaf node has been revoked; and decrypting the encrypted contents based on a response to the request. Therefore, even when the data storage capacity of a device is small or the data processing capability thereof is low, the contents encrypted according to a broadcast encryption scheme can be decrypted.