| 摘要 |
PROBLEM TO BE SOLVED: To provide a hierarchical inner product cipher technology based on a lattice problem, whose key size and cipher text size are small.SOLUTION: Key size and cipher text size are suppressed by making a parameter R of inner product cipher into GF(q). As a result, the key size becomes &OHgr;(μnlgq), and the cipher text size becomes &OHgr;(μn lgq). Even when it is required that 1/|R| can be ignored, it becomes that 1/|R|=1/q, it can be ignored. Even in such a case, it can be put that q=poly(n), and thereby, the key size &OHgr;(μnlgn), the cipher text size &OHgr;(μn lgn) can be achieved. |
