| 摘要 |
A method of encrypting data to be accessed only by a group of users comprises a user in the group receiving a user secret s i = fi(R, u i ), the user secret having been created by operating a first one-way function f1 on parameters comprising a root key R and a public identifier u i for the user. The user in the group receives a public identifier u i for each of the other users in the group. The user in the group obtains a group key by operating a second one-way function f2 on parameters comprising the user secret s,- and the public identifiers for the other users in the group u1, u2,...,uj-1,uj+1... un-1,un, wherein said second one-way function/band said first one-way function f 1 satisfy: f 2 (f 1 (R,u 1 ), u 2 ,...,u n ) = f 2 (f 1 (R,u 2 ),u 1 , u 3 , u 4 ...,u n )=... = f 2 (f 1 (R,u n ),u 1, u 2 ..., un-1). The user in the group encrypts the data using the group key.
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