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Telephone Network Security and the Capn Crunch whistle in the 1960s and early 1970s.

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Presentation on theme: "Telephone Network Security and the Capn Crunch whistle in the 1960s and early 1970s."— Presentation transcript:

1 Telephone Network Security and the Capn Crunch whistle in the 1960s and early 1970s

2 Overview The telephone network topology. Telephone switch signaling protocols. What is Phone Phreaking? Hacking the telephone network of the 1960s and 1970s. What was done to fix the problem.

3 The Telephone Network of the 1960s and early 1970s Primary function of a telephone network is to connect telephones together. Not feasible to connect every user to every other user directly. A network is needed. Hierarchical Network.

4 Hierarchical Network

5 Lowest level – end users connected to local exchange. Next level up – local exchanges connected to the primary trunk exchanges. Next level up – the primary trunk exchanges connected to the secondary trunk exchanges. Can extend to as many levels as needed.

6 Signaling Signaling is the means by which routing information is sent to switches. Two main types of signaling. – Local-loop signaling – Interoffice signaling Signals were sent on the same line that was used to transmit voice.

7 Signaling Cont. In order to reduce the probability that a human voice will mimic switch signals, special tone pairs were used.

8 Local-Loop Signaling User picks up a telephone and dials a number. Two types –Rotary –Push Button The switch at the local exchange routes the number.

9 Push Button Local Loop Signaling

10 Phone Phreaking Phreaking – 1. The art and science of cracking the phone network (so as, for example, to make free long-distance calls.) 2. By extension, security-cracking in any other context (especially, but not exclusively, on communication networks)

11 Interoffice Signaling A different signaling protocol is needed to prevent a user from sending signals to switches downstream.

12 Interoffice Signaling

13 The Blue Box Codes for interoffice signaling were published in a Bell Labs journal article. A box with 7 buttons could be built to route a call anywhere in the world! The first device confiscated by the phone company was blue. Steve Wozniak was in the Blue Box business.

14 A Blue Box Device

15 How to make a free phone call Phone Local Exch. Account. System Primary Exch. Secondary Exch. Primary Exch. Local Exch. Phone 1(800) KP-187-ST KP-07-STKP-095-ST KP ST Ring

16 Was the telephone system a secure network? The routing signals are sent over the same lines that carry voice signals (in-band). Cost must have been a factor. Not only free calls –Bouncing calls between switches (untraceable) –Flooding the network (Denial of service)

17 How was it fixed? By 1976 virtually all interoffice trunks were converted to a new type of signaling – Common Channel Interoffice Signaling Interoffice signals sent over separate lines.

18 Benefits of CCIS Reduces call time set up. Eliminates false customer simulated in-band signaling. Send data out of band, parallel to the voice circuit.

19 What about the Capn!?!

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