. "Then, server S can decide whether x ??? y or not by comparing (p, p, ---, p)n-th elements of En(k, x) and En(k, y) without decrypting them, i.e. En(k, x) and En(k, y) preserve the order between x and y, and (p, p, ---, p)n-th elements of encryption forms constitute order indicators." . . . .