Abstract: An encrypting and decrypting system employing analog signals in which delay lines are employed in both the encrypter and decrypter so that the initial analog signal which is received may be switched by switching means to a writer means where encrypting occurs in a delay line in which stages are filled in a predetermind clock period. Another delay line similar to that used for the writer means and this other delay line is used for reading the written stages from the first delay line according to the predetermined time distribution. Decrypting is carried out by inverting the foregoing encrypting operations. Various types of cynchronization are shown. Both read and write controls are shown.