Three-way call detection using steganography
First Claim
1. A three way call detection system for detecting the addition of a third party to an pre-existing telephonic connection between a first party and a second party, said system comprising:
- an ID generator for generating identification data;
a spread spectrum modulator for imposing the identification data onto a carrier signal, said modulator outputting a modulated identification signal having frequency components that are capable of being transmitted via a telephonic connection;
a source telephone for participating in a telephone conversation;
a signal combiner for adding the modulated identification signal to the telephone conversation to form an encoded telephone signal, the modulated identification signal being imperceptible to a human listener of the telephone conversation;
a remote telephone for receiving the encoded telephone signal; and
a spread spectrum demodulator for demodulating the modulated identification signal to extract the identification data.
18 Assignments
0 Petitions
Accused Products
Abstract
Three-way call detection is an important component of correctional facility telephone equipment because it helps restrict calling access by certain persons to certain restricted telephone numbers. Various three-way call detection methods exist, but all of these implementations suffer from one major limitation—the detection accuracy is not as high as is desired by the industry. The present invention improves detection accuracy, using “steganography.”Steganography involves hiding one set of data or signals within another signal or carrier in such a way that its presence is virtually imperceptible to the end recipient, and potential even the originator of the carrier signal. Television producers use steganographic methods to encode data in video signals for security, distribution monitoring, piracy-control, and other reasons. The present invention involves a device that connects to a telephone, either at the line or handset interfaces, and produces a known signal that is steganographically hidden within the user'"'"'s normal voice signal. Detection equipment, residing at another location, monitors signals on telephone calls and tests for the presence of the hidden signal or data generated by the invention. Once detection is achieved, appropriate action, such as terminating or recording the call, may be taken. Improved accuracy is achieved by choosing the appropriate hidden signal(s)—ones that never occur in the course of normal conversation and never get generated by telephone company equipment. Once detected, the presence of the signal guarantees the call was made to the restricted party from a particular phone line.
91 Citations
43 Claims
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1. A three way call detection system for detecting the addition of a third party to an pre-existing telephonic connection between a first party and a second party, said system comprising:
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an ID generator for generating identification data;
a spread spectrum modulator for imposing the identification data onto a carrier signal, said modulator outputting a modulated identification signal having frequency components that are capable of being transmitted via a telephonic connection;
a source telephone for participating in a telephone conversation;
a signal combiner for adding the modulated identification signal to the telephone conversation to form an encoded telephone signal, the modulated identification signal being imperceptible to a human listener of the telephone conversation;
a remote telephone for receiving the encoded telephone signal; and
a spread spectrum demodulator for demodulating the modulated identification signal to extract the identification data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for detecting the addition of a third party to an pre-existing telephonic connection between a first party and a second party, said method comprising:
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generating identification data;
subdividing the identification data into a plurality of subdivisions;
encoding the plurality of subdivisions on a modulated identification signal, the modulated identification signal comprising the subdivisions of the identification data encoded on a plurality of frequency bands using the predetermined sequence;
adding the modulated identification signal to a telephone signal to form an encoded telephone signal, the modulated identification signal being imperceptible to a human listener of the telephone signal;
transmitting the encoded telephone signal across a telephonic connection;
receiving the encoded telephone signal at a remote location;
extracting the modulated identification signal from the encoded telephone signal;
demodulating the modulated identification signal to extract the plurality of subdivisions of the identification data; and
assembling the plurality of subdivisions of the identification data to re-create the identification data using the predetermined sequence.
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10. A system for identifying a source telephone, said source telephone having identification data associated therewith, the system comprising:
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a spread spectrum modulator for encoding the identification data into a spread spectrum signal using a spreading code; and
a telephone interface for coupling to a telephone to add the spread spectrum signal to an output of the telephone. - View Dependent Claims (11, 12, 13, 14, 16, 17, 18)
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15. A system for decoding a modulated identification signal imbedded in a telephone signal wherein the identification signal is capable of identifying a source of the identification signal, the system comprising:
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a receiver for receiving a telephone signal, which telephone signal comprises an audio signal and a modulated identification signal, said modulated identification signal having identification data embedded therein; and
a spread spectrum demodulator for demodulating the modulated identification signal to extract the identification data.
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19. A method for identifying a source telephone, the method comprising:
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providing a data identification pattern for identifying a source telephone;
generating a reference spreading code using a random number generator;
encoding the data identification pattern into an identification signal using the spreading code and a spread spectrum modulator, thereby generating a modulated identification signal;
combining the modulated identification signal with an audio signal of a microphone output of a telephone to form a composite telephone signal, the modulated identification signal being imperceptible to a human listener of the composite telephone signal; and
transmitting the composite telephone signal across a telephonic connection. - View Dependent Claims (20, 21, 22, 23, 24)
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25. A method for identifying a source of a telephone signal received by a remote telephone, the method comprising:
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receiving a composite telephone signal from a source telephone at a remote location, the composite telephone signal comprising an audio signal representative of a telephone conversation and a modulated identification signal, the modulated identification signal having identification data that was embedded therein using a reference spreading code;
extracting the modulated identification signal; and
analyzing the extracted modulated identification signal to determine if the identification signal contains data that matches at least one of a predetermined set of restricted data signals. - View Dependent Claims (26, 27, 28, 29)
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30. A three way call detection system for detecting the addition of a third party having a third phone to an pre-existing telephonic connection between a first party having a first phone and a second party having a second phone, said system comprising:
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an ID generator for generating identification data;
a spread spectrum modulator for imposing the identification data onto a carrier signal, said modulator outputting an identification signal having frequency components that are capable of being transmitted via a telephonic connection;
a signal combiner for adding the identification signal to an output from a microphone of the first phone, thereby producing a combined output signal, said identification signal being added at a level that is imperceptible to a human ear that hears the combined output signal;
a signal receiver coupled to a third phone, for receiving the combined output signal after transmission across a telephonic connection from the first phone to the third phone;
a spread spectrum demodulator for demodulating the identification signal to extract the identification data; and
a processor to analyze the identification data. - View Dependent Claims (31, 32, 33, 34, 35, 36)
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37. A detection system for detecting a telephonic connection between a first phone and a second phone, said system comprising:
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an ID generator for generating identification data;
a spread spectrum modulator for imposing the identification data onto a carrier signal, said modulator outputting an identification signal having frequency components that are capable of being transmitted via a telephonic connection;
a signal combiner for adding the identification signal to an output from a microphone of a first phone, thereby producing a combined output signal, said identification signal being added at a level that is imperceptible to a human ear that hears the combined output signal;
a signal receiver for receiving the combined output signal after transmission across a telephonic connection;
a spread spectrum demodulator for demodulating the identification signal to extract the identification data; and
a processor to analyze the identification data. - View Dependent Claims (38, 39, 40, 41, 42, 43)
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Specification