The XOR cipher is the simplest cipher circuit around.The right group of XORs ciphers the message,while the left group deciphers it.You choose a 4 bit number and a 4 bit key,then the right group of LEDs shows the ciphered message.After you know the ciphered message,go to the left group of XORs and put the the chosen key.The left group of LEDs,should show the original message.In this example the input message is 0110 and the key is 1101.(The upper position of the switches is connected to the supply,and the down position is connected to the ground.)
