Analysis on security of a class of unbalanced Feistel ciphers

To evaluate the security of a class of unbalanced Feistel cipherst,he security analysis against differential and lin-ear attacks is investigated deeply using enumeration method.If the round function is bijectivet,hen the number of active round function for 3,4,6,8,10,2r(r≥3)-round ciphers is not less than 1,1,3,4,5r,respectively.So the upper bounds of maxi-mum differential and linear characteristic probabilities for 2r(r≥3)-round ciphers are pr and qr respectively if maximum differ-ential and liner approximation probabilities for round function are p and q.