Improved Identity-Based Broadcast Encryption

개선된 Identity 기반의 브로드캐스트 암호화 기법

The primitive of Identity-Based Broadcast Encryption allows a sender to distribute session keys or messages for a dynamically changing set of receivers using the receiver's identity as a public key. We already know that the trade-off exists the efficiency between the public parameter size and the ciphertext size. So, if the ciphertext size is O(1), then the public parameter size may be O(n). Some of IBBE scheme take the public parameters as input in decryption phase. Thus, a decryption device (or client) has to store the public parameters or receive it. This means that a decryption device (or client) has to have the proper size storage. Recently, delerabl$\square$e proposed an IBBE which have the O(1) size ciphertexts and the O(n) size public parameters. In this paper, we present an IBBE scheme. In our construction the ciphertext size and the public parameter size are sub-linear in the total number of receivers, and the private key size is constant.