Abstract: The broadcast encryption scheme was required to minimize the amount of decryption computation by many applications. Concerning this requirement, a new broadcast encryption scheme was proposed by using secret sharing in another way. The improved scheme reduced the amount of decryption computation by pre-reconstructing the interpolation share. Analysis shows that the improved scheme just needs to encrypt once the plaintext, and then the subscribers can decrypt the cipher text using their secret keys with less computation. The improved scheme can also remove and add subscribers securely without the changing of subscribers' secret keys, and is of collusion-resistant property.

Key words: broadcast encryption, secret sharing, collusion-resistance, discrete logarithm, pay-TV

摘要： 现在，越来越多的应用要求广播加密方案的解密算法的计算量尽可能小。针对这一需求，给出了秘密共享在广播加密中的另一种应用，通过预先重构插值份额，从而减少解密时重构的计算量。分析表明，改进后的方案只需对明文进行一次加密，授权用户利用各自私钥就能进行解密，而且解密时只需较小的计算量，并能实现安全地剔除用户、添加用户，而不需要授权用户改变私钥，能抗合谋攻击。

关键词: 广播加密, 秘密共享, 抗合谋性, 离散对数, 付费电视