9. The apparatus according to claim 8 , wherein the first virtual keyboard generating unit comprises at least one of: a key-character associations generating unit configured to randomly generate associations between keys on the first virtual keyboard and characters; and a layout generating unit configured to randomly generate a key layout of the first virtual keyboard.
10. The apparatus according to claim 9 , wherein the key-character associations generating unit comprises at least one of: a unit configured to randomly assign characters to keys on the first virtual keyboard; and a unit configured to randomly determine the number of characters associated with a key on the first virtual keyboard.