There are a number of PKC based broadcast encryption schemes. The original was the Franklin-Boneh scheme, google it. These more recent ones seem to promise improvements.
Identity-based broadcast encryption with constant size ciphertexts and private keys by C Delerablée, Asiacrypt 2007
The broadcaster encrypts messages and transmits these to the group of users via the broadcast channel. In a (public-key) IBBE encryption scheme, the broadcaster does not hold any private information and encryption is performed with the help of a public key PK.
Cited by 299
Public Key Broadcast Encryption Schemes With Shorter Transmissions, JH Park et. al., IEEE Transactions on Broadcasting, 2008.
Broadcast encryption allows a sender to securely distribute messages to a dynamically changing set of users over an insecure channel. In a public key broadcast encryption (PKBE) scheme, this encryption is performed in the public key setting, where the public key is stored in a user's device, or directly transmitted to the receivers along with ciphertexts. In this paper, we propose two PKBE schemes for stateless receivers which are transmission-efficient. A distinctive feature in our first construction is that, different than existing schemes in the literature, only a fraction of the public key related to the set of intended receivers is required in the decryption process. This feature results in the first PKBE scheme with O(r) transmission cost and O(1) user storage cost for r revoked users.. By combining the two proposed schemes, we suggest a PKBE scheme that achieves further shortened transmissions, while still maintaining O(1) user storage cost. The proposed schemes are secure against any number of colluders and do not require costly re-keying procedures followed by revocation of users.