Two novel cryptographic modes are presented in which a perturbation of the encrypted character stream (b) always results in a permanent perturbation of the output stream (c) of the decryption device. Two options are presented: feedback of the encryption character stream (d and e, respectively) and simultaneously feeding back, in accordance with a function f, (option 1) the encrypted character stream (b) or (option 2) the original character stream (a) to the encryption side and, respectively, the output character stream (c) to the decryption side.