The passwords for all the 22 levels are:
 
 Level  1   No Password     Level  2   VQVQFDE
 Level  3   ICIGCAA         Level  4   ECPQPCC
 Level  5   FTWKFEN         Level  6   HQWFTFW
 Level  7   DWNDGBW         Level  8   JCJCJHM
 Level  9   ICVGCGT         Level 10   LQPCUJV
 Level 11   HNWVGKB         Level 12   FTQKVLE
 Level 13   DCPLQMH         Level 14   EWDGPNL
 Level 15   TCNGTOV         Level 16   TCVQRPM
 Level 17   IQDNKQO         Level 18   KKKPURE
 Level 19   NGOGKSP         Level 20   NNGWTTO