Abstract:
A voice data security method and apparatus of the present invention modifies a subject voice data stream. Modification is by insertion of noise or similar interference effects. The amount of audio distortion is controllable. Audio or voice communications over a data network are thus made secure, and unauthorized use of the data network over voice channels is prevented.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Today various personnel of large companies or in corporate settings use computers. Many of these people like to have access to computer services outside of the corporate setting (e.g., web sites, e-mail, and chat rooms). To enable outside access, the corporate information technology (IT) staff sets up firewalls and bastion hosts between the internal and external networks that prevent unauthorized use or entry, yet still allow employees access to useful network resources.  
         [0002]     For example, company ABC&#39;s IT policy can be approximated as: (a) internal machines are allowed to directly initiate TCP connections to external machines on a specific subset of TCP ports, (b) internal machines may be allowed to use approved proxy hosts for accessing a more general set of external services (e.g., web access), (c) external machines are allowed to tunnel into the company&#39;s network only if they have provided appropriate authentication and are running IT-approved software configurations, and (d) e-mail from external machines is routed through appropriate bastion hosts and scanned for viruses. It is important to note that the only unauthenticated form of communication that is initiated by an external party is e-mail, accordingly e-mail is carefully checked before being delivered to employees to ensure security of ABC&#39;s (the company) network.  
         [0003]     Now consider the problem with respect to voice-over-internet protocol (VoIP). The VoIP telephone or VoIP-enabled computer is on an employee&#39;s desk and belongs to the internal corporate network. However, to be useful as a telephone, this same device should be able to receive VoIP telephone calls from people outside of the corporation (e.g., external call). Typically this functionality is implemented by placing a bastion host at the firewall that receives incoming telephone calls and forwards them to the appropriate internal VoIP equipment.  
         [0004]     An incoming VoIP telephone call consists of two logical parts: a signaling channel and a bi-directional voice (audio communication) data stream. Current bastion host technology processes the signaling channel and verifies that it appears to be an honest telephone call before passing it on to the end client. However, the voice or media data stream is forwarded without any further security measures. An example of this is, no determination is made to ensure that the data/media stream is in fact what it purports to be, i.e., an audio telephone call or voice data.  
         [0005]     The natural concern of IT staffs in general is that the voice data stream could be used for something other than voice data. It is plausible that an individual outside of the corporation could send a corrupted media stream to an internal VoIP client and attempt to exploit buffer-overrun attacks or other known problems with internal clients. For example, some VoIP telephones or soft telephones (software operating as telephones) have been known to reboot upon receiving a bad data stream. In addition, many soft telephones have known problems that can result in unintended actions on a client machine, such as running out of memory or greatly slowing down the machine. Given these known problems, it is not implausible that someone could inject a virus or remotely gain access to an improperly secured client machine using a voice data stream.  
         [0006]     Current firewall and bastion host implementations act as gatekeepers but do not modify or validate the voice data stream, so there are no safeguards once the call has been set up and the media stream established. The present invention provides such safeguards for both incoming and outgoing audio data streams.  
         [0007]     A somewhat similar type of data handling may be found in other fields. For example, web proxy servers may inspect and modify or delete elements from HTTP data streams. Further, some e-mail servers may be configured to delete viruses from e-mail or detect and delete spam.  
       SUMMARY OF THE INVENTION  
       [0008]     There is a need for solutions that implement audio communication security by modifying the subject data streams. The present invention provides such a voice data security system and method. In particular, the present invention provides audibly insignificant transmogrification of voice communications over data networks to prevent unauthorized usage of the network.  
         [0009]     In one embodiment of the present invention, the voice data security system includes a voice data stream and a signal modification engine responsive to the voice data stream, the signal modification engine modifying the voice data stream in a manner such that the amount of audible distortion to the voice data stream is controllable. The signal modification engine can introduce noise data, frequency noise data, and/or phase shift noise data into the voice data stream. The signal modification engine can also apply time dithering to the voice data stream. If desired, the amount of time dithering can maintain frequency content of the voice data stream. The signal modification engine can modify a silence duration of the voice data stream.  
         [0010]     The signal modification engine can further decode the voice data stream to a common format prior to modifying the voice data stream, and can encode the voice data stream after modifying the voice data stream. The signal modification engine encoding the voice data stream can restore the voice data stream to the original encoding format. Further, the signal modification engine can transcode the voice data stream to a different format for the voice data stream.  
         [0011]     The signal modification engine can provide the modified voice data stream to a telephony network. The telephony network can include voice-over IP equipment. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.  
         [0013]      FIG. 1  is a schematic view of a VoIP network employing voice data security of the present invention.  
         [0014]      FIG. 2  is a schematic view of a VoIP network with a firewall directing the subject voice data stream, the network employing an embodiment of the present invention voice data security.  
         [0015]      FIG. 3  is a flow chart of the present invention voice data security process which includes modification of a subject voice data stream.  
         [0016]      FIG. 4  is a block diagram of a signal modification engine of the present invention.  
         [0017]      FIG. 5  is a block diagram of a signal modification engine of another embodiment of the present invention which decodes and re-encodes the voice data stream during the process of generating a secured voice data stream. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     The present invention provides a low-cost solution that directly prevents unauthorized use of a data network over voice channels. It prevents many direct attacks on receiving audio communication equipment by protecting directly against standard attacks that rely on the integrity of the data stream. For example, a standard buffer-overflow attack relies on being able to insert a small piece of valid machine code in a known location outside of the data buffer. This invention modifies the data stream to the point that this form of attack is not practical.  
         [0019]     By way of general overview, one embodiment of the present invention includes a computer having one or more network interfaces (e.g., high speed) and a signal modification engine. The signal modification engine modifies audio streams in such a way as to be virtually undetectable to a human listener. The signal modification engine may work directly on the encoded audio data stream, or may optionally decode the audio data stream to a common format, introduce the modifications and re-encode the audio data stream to either the original format or a different format. The audio data stream modifications may include any or all of the following (but are not limited to): (1) introduction of a small quantity of “white” or audio noise, (2) introduction of a small amount of time dithering (e.g., expanding and contracting small time slices), (3) introduction of a small amount of time dithering without modifying frequency content, (4) introduction of a small quantity of frequency shift noise, (5) introduction of a small quantity of phase shift noise, and (6) introduction of small changes in silence duration.  
         [0020]     In general, the audio data stream modifications can be treated as some generalized digital filter applied against the audio data stream with the objective of changing the underlying data bits without noticeably degrading the audio quality. The amount of degradation can be varied to suit the use and security requirements of the installation, i.e. controllable degradation. If an initial audio stream is true audio data, a human receiving the invention modified audio stream will, at worst, think that the telephone connection is not as clear as it should be. On the other hand, a random bit pattern (of the present invention) introduced into a virus in the process of being transferred will almost certainly prevent the virus from succeeding.  
         [0021]      FIG. 1  is illustrative. In  FIG. 1 , a VoIP network  100  carries a subject voice data stream  102  initiated from a VoIP device  101 . The voice data stream  102  is indicative of a voice or audio communication (e.g., incoming or outgoing phone call). In one embodiment, the voice data stream  102  is sent to or received by (through a routing network  103 ) an invention voice data security system  104  for processing using a high-speed network interface (not shown). Similarly, in another embodiment of the present invention, system  104  may have more than one high-speed network interface.  
         [0022]     The voice data security system  104  includes a signal modification engine  106 . The signal modification engine  106  is responsive to the received voice data stream  102  and modifies voice data stream  102  to a modified voice data stream  102 ′. After modifying voice data stream  102 , the signal modification engine  106  forwards (through a routing network  103 ) the modified voice data stream  102 ′ to a VoIP device  108 . The VoIP device  108  can be a VoIP telephone and/or VoIP enabled computer system. In one embodiment, the voice data stream can be transmitted over the same routing network  103 . The routing network  103  can be the internet, intranet, or other known routing network.  
         [0023]     In another embodiment, after receiving the resulting voice data stream  102 ′, a computer system can establish a telephone connection such that the incoming/outgoing phone call can be received at a corresponding VoIP device  108 . Thus, the signal modification engine  106  forwards (through the routing network  103 ) the resulting (modified) voice data stream  102 ′ to a component of the network  100  for connection, i.e., receiving the incoming/outgoing telephone call. It should be understood that the network  100  can be a bidirectional network or a unidirectional network.  
         [0024]      FIG. 2  is a diagram of a VoIP network  200  employing voice data security of the present invention and using a firewall  202  to the direct voice data stream  102 . In one embodiment, the firewall  202  initially receives (through the routing network  103 ) and then directs the voice data stream  102  to the signal modification engine  106  for security processing (i.e., modification). After processing voice data stream  102 , the signal modification engine  106  can return the processed or modified voice data stream  102 ′ to the firewall  202  for forwarding or the signal modification engine  106  can forward the modified voice data stream  102 ′ directly. The firewall  202  or the signal modification engine  106  then directs the security processed/modified voice data stream  102 ′ to the appropriate destination in the same way as described for  FIG. 1 .  
         [0025]      FIG. 3  is a flow diagram  300  of the signal modification engine  106  (of  FIG. 1 ) process of modifying a voice data stream  102 . At step  302 , a voice data stream  102  exists on a network. The voice data stream  102  is received by the signal modification engine  106  in step  304 . Upon receiving the voice data stream  102 , the signal modification engine  106  modifies the voice data stream  102  by introducing interferences or noise (step  306 ) into the voice data stream  102 . At step  308 , the signal modification engine  106  delivers to an appropriate destination (step  310 ); a modified voice data stream  102 ′ having audio differences. The amount of degradation of the audio differences is controllable. In this way, the voice data stream  102  is made secure without noticeably degrading audio quality.  
         [0026]     Referring to  FIGS. 1 and 2 , a voice data security system  104  employs a signal modification engine  106  to modify a voice data stream  102  by inserting noise or interference into the voice data stream  102 . An expanded view of the signal modification engine  106  is shown in  FIG. 4 . In one embodiment, as illustrated in  FIG. 4 , the signal modification engine  106  introduces a single interference or type of suitable noise. Examples include, but are not limited to: (1) introduction of a small quantity of audio or white noise  406 , (2) introduction of a small amount of time dithering  408  for expanding and contracting small time slices, (3) introduction of a small amount of time dithering  408  for expanding and contracting small time slices without modifying frequency content, (4) introduction of a small quantity of frequency noise  410 , (5) introduction of small changes in silence duration  412  lengthening or shortening pauses, (6) introduction of a small quantity of phase shift noise  414  and (7) introduction of other types of interference  416 . Known techniques for implementing these examples are employed. Any combination of the foregoing and similar examples may be used by signal modification engine  106 .  
         [0027]     The amount of degradation (in resulting audio/voice communication stream  102 ′) from applying these interferences can be varied (controllable) to suit the use and security requirements of the network  100  (environment). In this way, the present invention voice data security system  104  prevents many direct attacks on receiving audio communication equipment  108 ,  110 ,  112  and prevents unauthorized use of a data network via voice channels.  
         [0028]      FIG. 5  shows an expanded view of a signal modification engine  502  that may decode and re-encode the voice data stream  102  during the process of generating a secured/modified voice data stream  102 ′. The signal modification engine  502  for the most part is similar to the signal modification engine  106  of  FIG. 4 . However, the signal modification engine  502  may decode the incoming voice data stream  102  in step  506  prior to introducing interferences  406 ,  408 ,  410 ,  412 ,  414  and/or  416 . For example, incoming voice data stream  102  is decoded into an audio wave form of certain or predetermined format, and then interferences  406 ,  408 ,  410 ,  412 ,  414 , and/or  416  are applied.  
         [0029]     After the signal modification engine  502  introduces the interference, the signal modification engine  502  may re-encode the modified voice data stream  102 ′ to the original format of the voice data stream  102  in step  520 . The resulting modified voice data stream  102 ′ is forwarded to the appropriate destination for voice/audio communication connection as described and shown in  FIGS. 1 and 2 .  
         [0030]     In another embodiment, transcoding and transmogrification can be combined. The signal modification engine  502  re-encodes the modified voice data stream  102 ′ to a different encoding format (at step  520 ). The resulting modified voice data stream  102 ′ in the different format is forwarded to the appropriate destination for voice/audio communication connection as shown in  FIGS. 1 and 2 . In this way, the present invention is capable of providing secure voice data streams as well as reformatting the voice data stream for increased security if the encoding is randomly lossy. Transcoding with a randomly lossy encoder without transmogrification may also be employed to introduce controlled degradation and hence voice data stream security of the present invention.  
         [0031]     It will be apparent to those of ordinary skill in the art that methods involved in the present invention may be embodied in a computer program product that includes a computer readable and usable medium. For example, such a computer usable medium may consist of a read only memory device, such as a CD ROM disk or conventional ROM devices, or a random access memory, such as a hard drive device or a computer diskette, having a computer readable program code implementing steps  304 ,  306  and  308  of  FIG. 3  stored thereon.  
         [0032]     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.