One mechanism for increasing security is to use encryption technology. The data sent is modified so that it is not easily intercepted. So encryption is the process carried out to secure a message (called plaintext) into a hidden message (called ciphertext) is encryption (encryption) (Budi Raharjo, 2002). Ciphertext is a message that cannot be read easily. The more appropriate terminology used is “encipher”. The reverse process, to convert ciphertext to plaintext, is called decryption. A more appropriate terminology for this process is “decipher”. Based on how to process text (plaintext), ciphers can be categorized into two types: block ciphers and stream ciphers. Block ciphers work by processing data in blocks, where several characters / data are combined into one block. Each one block process produces one block output as well. Meanwhile the stream cipher works. In this paper I will give an example of encryption of telephone lines using the help of wireless-based password devices. The device that I will explain is SIGSALY, which is a device that can create a secure line for calling someone or in other words encrypting our telephone conversations.


At the outset, long-distance telephone communication was broadcast using a “A-3” voice scrambler developed by Western Electric. Germany has a hearing station on the coast of the Netherlands that can intercept and cut off A-3 traffic. [1]

Although telephone scrambles were used by both parties in World War II, they were known to be not very safe in general, and both parties often broke random conversations from the other side. Audio spectrum inspection using spectrum analyzers often provides significant clues to randomization techniques. The insecurity of most telephone scrambler schemes has led to the development of safer scramblers, based on the principle of disposable bearings.

A prototype was developed at Bell Telephone Laboratories, under the direction of A. B. Clark, assisted by British mathematician Alan Turing, [1] [2] and demonstrated to the US Army. The Army was impressed and gave Bell Labs a contract for two systems in 1942. SIGSALY began operating in 1943 and continued to operate until 1946.

We often see action films that are usually about the warfare of a high-ranking leader or leader in the film often asking “make me a safe channel” when making important urgent calls.

secure phone

One way to get the safe path is to use a machine called SISSALY at the Bel Telephone Laboratories during the second world war. The machine replaced high frequency radio communications that were initially thought to be safe and random in fact already able to be tapped by opposing forces.

So what is SIGSALY? “Consisting of 40 racks of equipment, weighing more than 50 tons, and displaying two turntables synchronized to shipments and receivers with an agreed time setting signal from the US Naval Observatory,” according to the National Security Agency historical records.

When someone asks for a safe channel the device will start playing the phone copy and there are 2 turntables working together one will mix the noise into the phone copy and one will reduce the noise. So if there is someone who has no right to listen to it they will only just listen to the noise and someone who has the right to listen to the phone will hear the phone call as usual. (Matthew Green, assistant research professor at the Jhons Hopkins Information Securit Institute.)

The noise value used for the encryption key was originally produced by a large mercury vapor rectification vacuum tube and stored on phonograph recordings. The notes are then duplicated, with the notes distributed to the SIGSALY system at both ends of the conversation. The notes function as SIGSALY’s “One Time Pad,” and their distribution is very controlled (even if confiscated, it won’t really matter, because only one pair of each has ever been produced). For testing and regulation purposes, a pseudo-random number generator system made of relays, known as “Threshing Machines”, is used.

Records are played on the turntable, but because the time – clock synchronization – between the two SIGSALY terminals must be precise, the turntable is not only about arranging 2 communications but the turntable rotation rate is also carefully controlled, and the record starts at a very specific time, based on time standards clock time. Because each recording only provides 12 key minutes, each SIGSALY has two turntables, with the second recording going “queued” while the first will “start”


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