A New Type of ID-based Encryption System and Its Application to Pay-TV Systems

We proposed a new type of ID-based encryption scheme. Our scheme is different from other schemes on that we use tamper resistant smart card to store the private key and do the decryption job for the users. The user knows nothing about the private key. Our scheme is identical to ElGamal encryption scheme, but using RSA framework to avoid ID replacement attack. In a way, our scheme can be regarded as new application for the widely deployed RSA system. By employing the skill introduced by Dodis and Fazio for converting symmetric broadcast encryption schemes into public key ones, we extend our scheme into an efficient broadcast encryption scheme and apply it to the pay-TV system. We show that our broadcast encryption scheme is efficient in some aspects. For example, public keys of our system are of the size O(1) and decryption cost for each receiver is one modular exponentiation.