Skipping, Cascade, and Combined Chain Schemes for Broadcast Encryption
Jung Hee Cheon, Nam-Su Jho, Myung-Hwan Kim, Eun Sun Yoo · IEEE Transactions on Information Theory · 2008
We develop a couple of new methods to reduce transmission overheads in broadcast encryption. The methods are based on the idea of assigning one key per each partition using one-way key chains after partitioning the users. One method adoptsskippingchainson partitions containing up toprevoked users and the other adoptscascadechainson partitions with layer structure. The scheme using the former has the transmission overhead [(r)/(p+1)]+ [(N-r)/(c)], which is less thanr/pifr>p2N/c. The scheme using the latter keeps the same transmission overhead with the subset difference (SD) scheme whenrapproaches 0, whereris the number of revoked users. Combining the two schemes, we propose a new broadcast encryption scheme whose transmission overhead is the same with that of the SD scheme for smallrand becomes smaller than that of the SD asrgrows. The scheme using skipping chains possesses an advantage that any number of new users can join any time at no cost for current users. Finally, we show that the proposed key assignment scheme satisfieskey-indistinguishabilityassuming pseudorandom generators.