Decryption In order to decrypt, data is essentially passed backwards through the network. Hence decryption is also of the form of an SPN all s-boxes must be bijective the subkeys are applied in reverse order and the bits of the subkeys must be moved around according to the permutation, Note also that the lack of the permutation after the last round ensures that the decryption network can be the same structure as the encryption network21 Decryption • In order to decrypt, data is essentially passed backwards through the network. Hence, decryption is also of the form of an SPN. • all S-boxes must be bijective, • the subkeys are applied in reverse order and the bits of the subkeys must be moved around according to the permutation, • Note also that the lack of the permutation after the last round ensures that the decryption network can be the same structure as the encryption network