A method and system for providing privacy in a publish-subscribe protocol is provided. A server receives from a third party a topic-based key associated with a tree structure having a pseudonym of a topic as a root and at least one client as a leaf. The server encrypts a key associated with a conditional oblivious transfer protocol using the topic-based key. The server encrypts an item with the key associated with the conditional oblivious transfer protocol. The server transmits the encrypted key and the encrypted item to a plurality of clients. The encrypted item is decryptable by the at least one client with the key associated with the conditional oblivious transfer protocol when the key associated with the conditional oblivious transfer protocol is decryptable with an interest-based key associated with a tree structure having a pseudonym of an interest as a root and the at least one client as a leaf.