Adaptively Secure Broadcast Encryption with Small System Parameters

We build the first public-key broadcast encryption systems that simultaneously achieve adaptive security against arbitrary number of colluders, have small system parameters, and have security proofs that do not rely on knowledge assumptions or complexity leveraging. Our schemes are built from either composite order multilinear maps or obfuscation and enjoy a ciphertext overhead, private key size, and public key size that are all poly-logarithmic in the total number of users. Previous broadcast schemes with similar parameters are either proven secure in a weaker static model, or rely on non-falsifiable knowledge assumptions.