An encryption unit and decryption unit located in an encryption/decryption device may be used both for encryption and decryption, without their effects canceling each other out when, between the decryption input of the decrypter and the encryption output of the encrypter. An encryption combiner maps the encryption result data block at the encryption output to a mapped encryption result data block according to an encryption combining mapping and is exemplarily used when encrypting. A decryption combiner maps the encryption result data block at the encryption output to an inversely mapped encryption result data block according to a decryption combining mapping which is inverse to the encryption combining mapping and is exemplarily used when decrypting.