Blue box (phreaking)

Cap'n Crunch , toy pipe (2600 Hz)

A blue box is an electronic circuit that can produce a 2600 Hertz tone. This tone was used by CCITT -v5-compatible exchanges (e.g. in the United States, Japan, and France) to indicate the forwarding of calls to one another. In phreaking , it was used to steal free phone calls . The switching technology used today generally no longer allows blue boxing .

Which was discovered Blue Boxing of Joybubbles (birth name Joseph Carl Engressia, Jr.) . Engressia discovered by accident that by whistling a four-stroke E (e ⁴ ) he could make free phone calls. This tone was used by the then telephone company AT&T in the 1960s to regulate line seizure. The hobbyist John T. Draper expanded the method with his own knowledge and unconsciously turned it into a subculture of hacking. John Draper later called himself Captain Crunch because the 2600 Hz tone with a plastic whistle out of a bag Cap'n Crunch cereal could be generated. Draper was arrested shortly afterwards by the FBI and subsequently given a five-year suspended sentence.

function

This blue box once belonged to Steve Wozniak , the co-founder of Apple, and is on display in the Computer History Museum

Was chosen in the 1960s to the 1980s in the US phone system, a phone number , which at the same exchange ( local exchange (ie one was) like your own phone connected local call , English local call ), the connection is made directly to the local exchange . These local calls were usually free of charge, regardless of how long the connection lasted. When dialing a phone number that outside their own mediation range (ie at a long distance call , English long distance call required), an area code. For this purpose, special signaling is used between the calling local exchange and the exchange at the destination, which indicates the connection request. This signaling took place in the US telephone system in the 1960s and early 1970s, initially with the help of 2600 Hz pulses, later with multi-frequency tones similar to the multi-frequency dialing method of a push-button telephone, which were transmitted to the remote exchange via a trunk line.

The Bluebox took advantage of the fact that these control signals were transmitted in the same analog voice channel that is also used for transmitting regular telephone calls. In this case, one speaks of analog inband signaling , in contrast to the digitally implemented outband signaling that is usually used later , also referred to as common channel signaling (CCS), in which the control information for switching is transmitted via its own data connections that are separate from the voice channel Tampering with the blue box technology is basically no longer possible.

This in-band signaling made it possible for a subscriber to send the tone sequences used by the exchanges for communication from an ordinary telephone and thus influence the exchanges. First of all, a 2600 Hz tone was generated with the Bluebox in order to get a free trunk line without dialing a preselection. Then you dialed the desired telephone number with 2600 Hz pulses - the principle was similar to pulse dialing , only with tones. This made it possible to bypass the meter at your own exchange, as it could only record long-distance calls dialed “normally” via a corresponding area code. Since telephone calls within the same local exchange were free anyway, the long-distance calls thus sneaked were completely free.

After the signaling protocol between the local exchanges had been converted to a multi-frequency method in the following years , Draper built so-called multi-frequency devices with which he could generate the different tones required. These devices were initially called MF boxes. The name Blue Box allegedly came about when Draper gave one of the first MF boxes to the blind boy Joe, who wanted to know the color of the device. Because Draper had built the frequency generator into an old blue box, Joe named the device the Blue Box . Later on, the term blue box was also used as a name for the method itself and became known worldwide as blueboxing .

Frequencies used

The following frequencies were used with Blue Box:

code	700 Hz	900 Hz	1100 Hz	1300 Hz	1500 Hz	1700 Hz
1	×	×
2	×		×
3		×	×
4th	×			×
5		×		×
6th			×	×
7th	×				×
8th		×			×
9			×		×
0 /10				×	×
11 / ST3	×					×
12 / ST2		×				×
KP			×			×
KP / ST2				×		×
ST					×	×

literature

• Phil Lapsley: Exploding the phone. The untold story of the teenagers and outlaws who hacked Ma Bell . New York, Berkeley 2013. ISBN 978-0-8021-2061-8 .

Web links

• The story of the Captain Crunch
• History of phone phreaking (English)

Individual evidence

1. ^ CCC - Hackerbibel , Part 1 from 1998, p. 208; and YIPL - Youth International Party Line, No. August 12, 1972, p. 2.