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
1 Petition
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 typically imperceptible to the human ear, and potential even the originator of the carrier signal. The present invention involves a device that connects to a telephone, either at the line or the 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). Once detected, the presence of the signal guarantees the call was made to the restricted party from a particular phone line.
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Citations
42 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 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 (10, 11, 12, 13, 14, 15, 16)
a comparator for comparing the identification data to a predetermined set of restricted data; and a restricted call response module for executing at least a selected one of the following responses if the identification data matches any of the predetermined set of restricted data;
(1) turning off a microphone of a telephone, (2) disconnecting a telephone call, (3) recording any conversation that may occur on a call, (4) playing a prerecorded message, (5) recording call data, (6) disabling the speaker of a telephone, and (7) adding a disruptive signal to a telephonic connection.
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16. The system of claim 13, further comprising:
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a code generator for generating a pseudo-random code; a spread spectrum modulator for imposing the identification data onto a carrier signal using the pseudo-random code, said modulator outputting a modulated identification signal having frequency components that are capable of being transmitted via a telephonic connection; and a signal combiner for adding the modulated identification signal to an audio signal of a telephone microphone, said combiner producing a telephone signal as an output.
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17. 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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18. 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 (19, 20, 21, 22, 23)
receiving the composite telephone signal from a source telephone at a remote location;
multiplying the composite telephone signal by the reference spreading code to form a signal product;filtering or correlating the signal product to extract the modulated identification signal from the digital data; and comparing the modulated identification signal with a predetermined set of restricted data signals to determine if the modulated identification signal matches at least one of a predetermined set of restricted data signals.
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20. The method of claim 19 further comprising:
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performing an envelope detection on the filtered signal product, if needed; and comparing the output of the envelope detection with a threshold value to determine if the signal product matches at least one of a predetermined set of restricted data signals.
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21. The method of claim 19 further comprising:
initiating a restricted call response if the signal product matches at least one of a predetermined set of restricted data signals, the restricted call response being selected from the group of following choices;
(1) turning off a microphone of a telephone, (2) disconnecting a telephone call, (3) recording a call, (4) playing a prerecorded message, (5) recording call data, (6) disabling the speaker of a telephone, and (7) adding a disruptive signal to a telephonic connection.
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22. The method of claim 19 wherein the step of receiving the composite telephone signal further comprises:
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providing an analog-to-digital converter; and converting the composite telephone signal from an analog signal to a digital signal.
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23. The method of claim 18 further comprising:
demodulating the modulated identification signal to extract the data identification pattern using a reference spreading code.
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24. 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 (25, 26, 27, 28)
multiplying the composite telephone signal by the reference spreading code to form a signal product; and extracting the modulated identification signal.
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26. The method of claim 25 further comprising:
initiating a restricted call response if the signal product matches at least one of a predetermined set of restricted data signals, the restricted call response being selected from the group of following choices;
(1) turning off a microphone of a telephone, (2) disconnecting a telephone call, (3) recording a call, (4) playing a prerecorded message, (5) recording call data, (6) disabling the speaker of a telephone, and (7) adding a disruptive signal to a telephonic connection.
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27. The method of claim 24 wherein the step of receiving the composite telephone signal further comprises:
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providing an analog-to-digital converter; and converting the composite telephone signal from an analog signal to a digital signal.
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28. The method of claim 24 further comprising:
demodulating the modulated identification signal to extract the identification data using a reference spreading code.
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29. 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 (30, 31, 32, 33, 34, 35)
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36. 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 (37, 38, 39, 40, 41, 42)
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Specification