Abstract: A ciphering system comprises a ciphering device having an input for a sequence of bits to be ciphered, and output for the ciphered bit sequence, and a mixing unit connected between the input and the output. The mixing unit receives both the bit sequence to be ciphered and a sequence of code bits for ciphering the bit sequence and, by a mixing operation, generates the ciphered bit sequence. The output of the mixing unit is connected to a first code unit for generating code bits. The first code unit comprises a memory addresses with bits from the ciphered bit sequence. The first code unit is furthermore connected to a second code unit, which comprises a memory containing code bits and the output of which is connected to the mixing unit. The deciphering device of the ciphering system is conceived in the same manner as the ciphering device, with the exception that the input of the code unit receives input signals from the input of the deciphering device.