| 摘要 |
<p>A processor (111) of a device (110) of user i in an aggregator-oblivious encryption system with n users encrypts a message x i , t †’ = x i , t , 1 ... x i , t , r where t denotes a time period by generating an encrypted value c i,t for the time period t , by calculating c i,t = g 1 xi,t ,1 ··· g r xi,t,r · H ( t ) Si , wherein H ( t ) is a hash function that hashes the time t on to an element of a first group G 1 with order q 1 in which discrete logarithms are are calculable only non-polynomial time for a security parameter º, wherein g 1 , ··· , g r is the base of a second group G 2 = Œ©g 1 , ···, g r Œª with order q 2 in which discrete logarithms are calculable in polynomial time, the first group G 1 and the second group G 2 both being different subgroups of a third group G, and wherein S i is a key for user i provided by a dealer so that an aggregator key s 0 = - ˆ‘ i = 1 n s i and outputs the encrypted value c i,t to an aggregator (120). The aggregator obtains the sum X t for time period t by first computing V t : = H t s 0 ˆ� i = 1 n c i , t = ˆ� i = 1 n ˆ� j = 1 r g j x i , t , j , and then X t †’ = X t , 1 ... X t , r with X t , j = ˆ‘ i = 1 n x i , t , j for each j ˆˆ{1,... , r }, as the unique representation of V t ˆˆ G 2 with regard to basis Œ© g 1 , ···, g r Œª.</p> |
