Attribute Based Broadcast Encryption (ABBE) is a combination
of Attribute Based Encryption (ABE) and Broadcast Encryption
(BE). It allows a broadcaster (or encrypter) to broadcast an encrypted
message that can only be decrypted by the receivers who are within a predefined
user set and satisfy the access policy specified by the broadcaster.
Compared with normal ABE, ABBE allows direct revocation, which is
important in many real-time broadcasting applications such as Pay TV.
In this paper, we propose two novel ABBE schemes that have distinguishing
features: the first scheme is key-policy based and has short ciphertext
and constant size decryption key; and the second one is ciphertext-policy
based and has constant size ciphertext and short decryption key. Both of
our schemes allow access policies to be expressed using AND-gate with
positive, negative, and wildcard symbols, and are proven secure under
the Decision n-BDHE assumption without random oracles.