Patent Publication Number: US-2023141773-A1

Title: Real Time Audio Stream Validation

Description:
BACKGROUND 
     1. Field 
     The disclosure relates generally to telephony and more specifically to validating that an audio stream of a voice communication corresponding to a call is authentic from a trusted source and has not been tampered with by verifying a hashed value of each respective block in a series of blocks comprising the audio stream. 
     2. Description of the Related Art 
     Telephony is the use and operation of devices, such as, for example, mobile phones, for transmission of voice communications between distant parties. Phone scams are increasing and have become more sophisticated over time, with new technologies and relative lack of regulatory protection of mobile phone numbers as compared to landline telephone numbers. It has been reported that over 40 percent of all calls are some type of scam call. Scam phone numbers are one of the most common forms of scam calls, as scam operations will use spoofing technology to generate a false phone number that a recipient of a scam call might trust. For example, a large percentage of scam callers utilize neighborhood spoofing that tricks caller ID to show area codes and telephone numbers local to recipients of these scam calls. By imitating local numbers, it makes a scam call appear legitimate, which tricks recipients into answering the call. This strategy increases the odds that scam callers will successfully get recipients to divulge sensitive information, such as, for example, banking information and the like. Scam calls have cost some recipients thousands of dollars. 
     SUMMARY 
     According to one illustrative embodiment, a computer-implemented method for real time audio stream validation is provided. A first voice communication device sends an audio stream of a voice communication corresponding to a call into a plurality of blocks in response to the first voice communication device receiving the audio stream from a user of the first voice communication device. The first voice communication device modifies the plurality of blocks to generate a first modified audio stream corresponding to the call that includes hashed values of the plurality of blocks. The first voice communication device sends the first modified audio stream along with the hashed values of the plurality of blocks to a second voice communication device via a network. According to other illustrative embodiments, a computer system and computer program product for real time audio stream validation are provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a pictorial representation of a network of data processing systems in which illustrative embodiments may be implemented; 
         FIG.  2    is a diagram of a data processing system in which illustrative embodiments may be implemented; 
         FIG.  3    is a diagram illustrating an example of an audio stream in accordance with an illustrative embodiment; 
         FIG.  4    is a diagram illustrating an example of a segmented audio stream in accordance with an illustrative embodiment; 
         FIG.  5    is a diagram illustrating an example of a block hashing process in accordance with an illustrative embodiment; 
         FIG.  6    is a diagram illustrating an example of a real time audio stream validation process in accordance with an illustrative embodiment; 
         FIG.  7    is a flowchart illustrating a process for validating hashed audio stream blocks in real time in accordance with an illustrative embodiment; and 
         FIG.  8    is a flowchart illustrating a process for hashing blocks of an audio stream in accordance with an illustrative embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention may be a system, a method, and/or a computer program product at any possible technical detail level of integration. The computer program product may include a computer-readable storage medium (or media) having computer-readable program instructions thereon for causing a processor to carry out aspects of the present invention. 
     The computer-readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer-readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer-readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer-readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire. 
     Computer-readable program instructions described herein can be downloaded to respective computing/processing devices from a computer-readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium within the respective computing/processing device. 
     Computer-readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the “C” programming language or similar programming languages. The computer-readable program instructions may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer-readable program instructions by utilizing state information of the computer-readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention. 
     Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer-readable program instructions. 
     These computer-readable program instructions may be provided to a processor of a computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer-readable program instructions may also be stored in a computer-readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer-readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be accomplished as one step, executed concurrently, substantially concurrently, in a partially or wholly temporally overlapping manner, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions. 
     With reference now to the figures, and in particular, with reference to  FIG.  1    and  FIG.  2   , diagrams of data processing environments are provided in which illustrative embodiments may be implemented. It should be appreciated that  FIG.  1    and  FIG.  2    are only meant as examples and are not intended to assert or imply any limitation with regard to the environments in which different embodiments may be implemented. Many modifications to the depicted environments may be made. 
       FIG.  1    depicts a pictorial representation of a network of data processing systems in which illustrative embodiments may be implemented. Network data processing system  100  is a network of computers, data processing systems, and other devices in which the illustrative embodiments may be implemented. In this example, network data processing system  100  represents a telecommunications network. Network data processing system  100  contains network  102 , which is the medium used to provide communications links between the computers, data processing systems, and other devices connected together within network data processing system  100 . Network  102  may include connections, such as, for example, wire communication links, wireless communication links, fiber optic cables, and the like. 
     In the depicted example, server  104  and server  106  connect to network  102 , along with storage  108 . Server  104  and server  106  may be, for example, server computers with high-speed connections to network  102 . Also, server  104  and server  106  may each represent a cluster of servers in one or more data centers. Alternatively, server  104  and server  106  may each represent multiple computing nodes in one or more cloud environments. In addition, server  104  and server  106  provide telecommunication services to client device users. 
     Client  110 , client  112 , and client  114  also connect to network  102 . Clients  110 ,  112 , and  114  are client devices of server  104  and server  106 . In this example, clients  110 ,  112 , and  114  are shown as mobile voice communication devices, such as, for example, smart phones, cellular phones, and the like, with wireless communication links to network  102 . However, it should be noted that clients  110 ,  112 , and  114  are examples only and may represent other types of voice communication systems, such as, for example, desktop or personal computers, laptop computers, handheld computers, smart televisions, smart vehicles, gaming systems, kiosks, and the like, with wire or wireless communication links to network  102 . Users of clients  110 ,  112 , and  114  may utilize clients  110 ,  112 , and  114  to access and utilize the telecommunication services provided by server  104  and server  106  to participate in voice communications with other client device users. 
     Further, clients  110 ,  112 , and  114  using illustrative embodiments are capable of validating that received audio streams of voice communications corresponding to calls are from trusted or legitimate sources (e.g., not scam calls) and have not been tampered with (e.g., unauthorized entities trying to join calls) by individually verifying hashed values of a series of blocks comprising the received audio streams. If illustrative embodiments determine that all hashed values of audio stream blocks of a call are valid, then illustrative embodiments allow the call to continue as usual. However, if illustrative embodiments determine that a hashed value of an audio stream block is invalid, then illustrative embodiments alert a user of the client device via, for example, at least one of a virtual assistant voice alert, text notification, on-screen pop-up, or the like and terminate the call. Thus, illustrative embodiments increase security of voice communications. 
     Storage  108  is a network storage device capable of storing any type of data in a structured format or an unstructured format. In addition, storage  108  may represent a plurality of network storage devices. Further, storage  108  may store identifiers (e.g., telephone numbers, voice over internet protocol addresses, and the like) for a plurality of client devices, identifiers for a plurality of client device users, and the like. Furthermore, storage  108  may store other types of data, such as authentication or credential data that may include usernames, passwords, and the like associated with client device users, for example. 
     In addition, it should be noted that network data processing system  100  may include any number of additional servers, clients, storage devices, and other devices not shown. Program code located in network data processing system  100  may be stored on a computer-readable storage medium or a set of computer-readable storage media and downloaded to a computer or other data processing device for use. For example, program code may be stored on a computer-readable storage medium on server  104  and downloaded to client  110  over network  102  for use on client  110 . 
     In the depicted example, network data processing system  100  may be implemented as a number of different types of communication networks, such as, for example, a telecommunications network, an internet, an intranet, a wide area network (WAN), a local area network (LAN), or any combination thereof.  FIG.  1    is intended as an example only, and not as an architectural limitation for the different illustrative embodiments. 
     As used herein, when used with reference to items, “a number of” means one or more of the items. For example, “a number of different types of communication networks” is one or more different types of communication networks. Similarly, “a set of,” when used with reference to items, means one or more of the items. 
     Further, the term “at least one of,” when used with a list of items, means different combinations of one or more of the listed items may be used, and only one of each item in the list may be needed. In other words, “at least one of” means any combination of items and number of items may be used from the list, but not all of the items in the list are required. The item may be a particular object, a thing, or a category. 
     For example, without limitation, “at least one of item A, item B, or item C” may include item A, item A and item B, or item B. This example may also include item A, item B, and item C or item B and item C. Of course, any combinations of these items may be present. In some illustrative examples, “at least one of” may be, for example, without limitation, two of item A; one of item B; and ten of item C; four of item B and seven of item C; or other suitable combinations. 
     With reference now to  FIG.  2   , a diagram of a data processing system is depicted in accordance with an illustrative embodiment. Data processing system  200  is an example of a voice communication device, such as client  110  in  FIG.  1   , in which computer-readable program code or instructions implementing the audio stream validation processes of illustrative embodiments may be located. In this example, data processing system  200  includes communications fabric  202 , which provides communications between processor unit  204 , memory  206 , persistent storage  208 , communications unit  210 , input/output (I/O) unit  212 , and display  214 . 
     Processor unit  204  serves to execute instructions for software applications and programs that may be loaded into memory  206 . Processor unit  204  may be a set of one or more hardware processor devices or may be a multi-core processor, depending on the particular implementation. 
     Memory  206  and persistent storage  208  are examples of storage devices  216 . As used herein, a storage device or a storage medium is any piece of hardware that is capable of storing information, such as, for example, without limitation, data, program code in functional form, and/or other suitable information either on a transient basis or a persistent basis. Further, a storage device or a storage medium excludes a propagation medium, such as transitory signals. Furthermore, a storage device or a storage medium may represent a set of storage devices or a set of storage media. Memory  206 , in these examples, may be, for example, a random-access memory (RAM), or any other suitable volatile or non-volatile storage device, such as a flash memory. Persistent storage  208  may take various forms, depending on the particular implementation. For example, persistent storage  208  may contain one or more devices. For example, persistent storage  208  may be a disk drive, a solid-state drive, or a combination thereof. 
     In this example, persistent storage  208  stores audio stream validator  218 . However, it should be noted that even though audio stream validator  218  is illustrated as residing in persistent storage  208 , in an alternative illustrative embodiment, audio stream validator  218  may be a separate component of data processing system  200 . For example, audio stream validator  218  may be a hardware component coupled to communication fabric  202  or a combination of hardware and software components. 
     Audio stream validator  218  controls the process of validating that an audio stream or a recording of the audio stream corresponding to a call is authentic and has not been tampered with by verifying a hashed value of each respective block in a series of blocks comprising the audio stream. As a result, data processing system  200  operates as a special purpose voice communication system in which audio stream validator  218  in data processing system  200  enables automatic audio stream validation for increased voice communication security. In particular, audio stream validator  218  transforms data processing system  200  into a special purpose voice communication system as compared to currently available general voice communication systems that do not have audio stream validator  218 . 
     Communications unit  210 , in this example, provides for communication with other computers, data processing systems, and devices via a network, such as network  102  in  FIG.  1   . Communications unit  210  may provide communications through the use of both physical and wireless communications links. The wireless communications link may utilize, for example, shortwave, high frequency, ultrahigh frequency, microwave, wireless fidelity (Wi-Fi), Bluetooth® technology, global system for mobile communications (GSM), code division multiple access (CDMA), second-generation (2G), third-generation (3G), fourth-generation (4G), 4G Long Term Evolution (LTE), LTE Advanced, fifth-generation (5G), or any other wireless communication technology or standard to establish a wireless communications link for data processing system  200 . The physical communications link may utilize, for example, a wire, cable, universal serial bus, or any other physical technology to establish a physical communications link for data processing system  200 . 
     Input/output unit  212  allows for the input and output of data with other devices that may be connected to data processing system  200 . For example, input/output unit  212  may provide a connection for user input through a keypad, a keyboard, a mouse, a microphone, and/or some other suitable input device. Display  214  provides a mechanism to display information to a user and may include touch screen capabilities to allow the user to make on-screen selections through user interfaces or input data, for example. 
     Instructions for the operating system, applications, and/or programs may be located in storage devices  216 , which are in communication with processor unit  204  through communications fabric  202 . In this illustrative example, the program instructions or program code are in a functional form on persistent storage  208 . These program instructions may be loaded into memory  206  for running by processor unit  204 . The program instructions, in the different embodiments, may be embodied on different physical storage devices, such as memory  206  or persistent storage  208 . 
     Program code  220  is located in a functional form on computer-readable media  222  that is selectively removable and may be loaded onto or transferred to data processing system  200  for running by processor unit  204 . Program code  220  and computer-readable media  222  form computer program product  224 . In one example, computer-readable media  222  may be computer-readable storage media  226  or computer-readable signal media  228 . 
     In these illustrative examples, computer-readable storage media  226  is a physical or tangible storage device used to store program code  220  rather than a medium that propagates or transmits program code  220 . Computer-readable storage media  226  may include, for example, an optical or magnetic disc that is inserted or placed into a drive or other device that is part of persistent storage  208  for transfer onto a storage device, such as a hard drive, that is part of persistent storage  208 . Computer-readable storage media  226  also may take the form of a persistent storage, such as a hard drive, a thumb drive, or a flash memory that is connected to data processing system  200 . 
     Alternatively, program code  220  may be transferred to data processing system  200  using computer-readable signal media  228 . Computer-readable signal media  228  may be, for example, a propagated data signal containing program code  220 . For example, computer-readable signal media  228  may be an electromagnetic signal, an optical signal, or any other suitable type of signal. These signals may be transmitted over communication links, such as wireless communication links, an optical fiber cable, a coaxial cable, a wire, or any other suitable type of communications link. 
     Further, as used herein, “computer-readable media  222 ” can be singular or plural. For example, program code  220  can be located in computer-readable media  222  in the form of a single storage device or system. In another example, program code  220  can be located in computer-readable media  222  that is distributed in multiple data processing systems. In other words, some instructions in program code  220  can be located in one data processing system while other instructions in program code  220  can be located in one or more other data processing systems. For example, a portion of program code  220  can be located in computer-readable media  222  in a server computer while another portion of program code  220  can be located in computer-readable media  222  located in a set of client computers. 
     The different components illustrated for data processing system  200  are not meant to provide architectural limitations to the manner in which different embodiments can be implemented. In some illustrative examples, one or more of the components may be incorporated in or otherwise form a portion of, another component. For example, memory  206 , or portions thereof, may be incorporated in processor unit  204  in some illustrative examples. The different illustrative embodiments can be implemented in a data processing system including components in addition to or in place of those illustrated for data processing system  200 . Other components shown in  FIG.  2    can be varied from the illustrative examples shown. The different embodiments can be implemented using any hardware device or system capable of running program code  220 . 
     In another example, a bus system may be used to implement communications fabric  202  and may be comprised of one or more buses, such as a system bus or an input/output bus. Of course, the bus system may be implemented using any suitable type of architecture that provides for a transfer of data between different components or devices attached to the bus system. 
     Illustrative embodiments are capable of resolving issues regarding scam calls, caller identification (ID) spoofing, and other types of social engineering to manipulate people into divulging confidential information. For example, scam calls can fake caller ID information. Consequently, when receiving a call from a purported bank, it would be advantageous if the called device could display a notification or pop up to the user to confirm that the call is actually from a legitimate bank corresponding to that user. Similarly, when a purported account holder calls a bank to obtain account information or the like, the bank needs to authenticate the caller prior to releasing any sensitive information. It would be advantageous if a device of a legitimate caller could perform the authentication to the bank automatically and seamlessly for the caller. Currently, many applications exist that perform call verification based on phone numbers or caller ID, but these applications are easily spoofed. As a result, an improved call verification process is needed to confirm or verify that a given call comes from a trusted source. 
     Illustrative embodiments monitor a call in the background by verifying a hashed value of each respective block in a series of blocks comprising an audio stream of the call (e.g., conversation) to determine whether the call is from a trusted source. An audio stream delivers real time audio (e.g., voice communication) between devices via a network connection (e.g., telecommunications network). This continuous verification of the audio stream by illustrative embodiments can prevent different types of attacks, such as, for example, man-in-the-middle attacks, third-party intrusions, and the like, which generate noise affecting the hash of a block in the audio stream. 
     To perform this continuous verification of the audio stream, illustrative embodiments segment, divide, or chunk the audio stream into a plurality of blocks (e.g., a sequential series of blocks). Illustrative embodiments can generate blocks of the same length or of a variable length depending on implementation. In addition, each respective block of the audio stream includes a hash of the block that directly or immediately preceded that block. Illustrative embodiments send the current block with the hash of the previous block to a device receiving the audio stream. Illustrative embodiments integrate the hash as a high frequency signal inside the audio stream similar to audio steganography. Audio steganography is a technique used to transmit hidden information by modifying an audio stream in an imperceptible manner. In other words, audio steganography is capable of hiding information in a host audio stream without interfering with the host audio stream. Alternatively, illustrative embodiments can send the hash as metadata via another telecommunications channel, such as, for example, evolved packet core or the like, to the device receiving the audio stream. 
     Illustrative embodiments calculate the hash of the first block in the audio stream and then add the hash of the first block to a second block of the audio stream. Illustrative embodiments then calculate a hash of the second block, which includes the hash of the first block, and add the hash of the second block to a third block of the audio stream, and so on. In this example, validation of the audio stream blocks is being performed on one side of the audio stream (e.g., the called device or the device receiving the audio stream). However, illustrative embodiment can perform the validation on both sides of the audio stream (e.g., on each device involved in the call). As a result, both participants of the call can know that they are communicating with a trusted or a legitimate person, device, entity, or the like. 
     Illustrative embodiments hash a block of the audio stream using a private cryptographic key corresponding to a user of a sending voice communication device (e.g., calling device). It should be noted that cryptographic keys are already shared or exchanged between the calling and called devices. Illustrative embodiments on the receiving voice communication device (e.g., called device) verify whether the received audio stream block was hashed with the correct private cryptographic key corresponding to the user of the sending voice communication device by utilizing a public key corresponding to the user of the sending voice communication device. As a result, illustrative embodiments enable continuous real time verification of the audio stream during the entirety of the call by individually analyzing each respective hashed audio stream block in the series of hashed audio stream blocks comprising the call. 
     Further, illustrative embodiments can detect the time when the audio stream becomes distorted or mingled by, for example, an unauthorized third party entering the call without permission. For example, illustrative embodiments can detect a minimal change in the audio stream, which may be caused by an intruder of the call, impacting the resultant hashed value of an audio stream block. As a result, illustrative embodiments can detect the invalid hashed audio stream block and provide an alert or warning to the user via a screen notification or pop up. Thus, illustrative embodiments are capable of detecting the time when the intrusion or man-in-the-middle attack occurred (e.g., when alteration in the hashed value of an audio stream block occurred). By using cryptographic keys, illustrative embodiments are capable of detecting the authenticity of the source or origin of a given audio stream. 
     As a result, illustrative embodiments resolve the issue of caller identification spoofing by correctly identifying legitimate calls. Thus, illustrative embodiments can protect against an attack in which a scam caller is wanting to obtain confidential information for later use (e.g., information misappropriation). 
     Furthermore, illustrative embodiments can be used to protect against copyright infringement when, for example, copyrightable material is transmitted during a call and a recorded copy of the call is available for verification by illustrative embodiments. Similarly, illustrative embodiments can be used for digital signature via voice in a recorded copy of a call. Moreover, illustrative embodiments can be used by additional applications for bidirectional authentication. 
     Thus, illustrative embodiments provide one or more technical solutions that overcome a technical problem with validating an audio stream of a voice communication corresponding to a call in real time to verify that the audio stream is from a trusted source and has not been tampered with. As a result, these one or more technical solutions provide a technical effect and practical application in the field of telephony security. 
     With reference now to  FIG.  3   , a diagram illustrating an example of an audio stream is depicted in accordance with an illustrative embodiment. Audio stream  300  may be implemented in a voice communication device, such as, for example, client  110  in  FIG.  1    or data processing system  200  in  FIG.  2   . 
     In this example, audio stream  300  represents a voice communication (e.g., spoken words) corresponding to a call initiated by a user of the voice communication device with a user of another voice communication device. It should be noted that audio stream  300  is intended as an example only and not as a limitation on illustrative embodiments. In other words, illustrative embodiments may utilize any type of audio stream, audio track, voice spectrum, audio file, or the like. 
     With reference now to  FIG.  4   , a diagram illustrating an example of a segmented audio stream is depicted in accordance with an illustrative embodiment. Segmented audio stream  400  may be implemented in a voice communication device, such as, for example, client  110  in  FIG.  1    or data processing system  200  in  FIG.  2   . 
     Segmented audio stream  400  represents an audio stream, such as, for example, audio stream  300  in  FIG.  3   , which is segmented by the voice communication device using, for example, an audio stream validator, such as audio stream validator  218  in  FIG.  2   . In this example, segmented audio stream  400  is comprised of block 1  402 , block 2  404 , block 3  406 , block 4  408 , block 5  410 , and block 6  412 . However, it should be noted that segmented audio stream  400  is intended as an example only and not as a limitation on illustrative embodiments. In other words, segmented audio stream  400  may include any number of blocks depending on the length of the audio stream corresponding to the call. 
     With reference now to  FIG.  5   , a diagram illustrating an example of a block hashing process is depicted in accordance with an illustrative embodiment. Block hashing process  500  may be implemented in a voice communication device, such as, for example, client  110  in  FIG.  1    or data processing system  200  in  FIG.  2   . 
     In this example, block hashing process  500  includes block 1  502 , block 2  504 , and block 3  506  of a segmented audio stream, such as, for example, block 1  402 , block 2  404 , and block 3  406  of segmented audio stream  400  in  FIG.  4   . Block hashing process  500  utilizes hashing algorithm  508  to generate hashed value  510  of block 1  502  based on private cryptographic key  512 . Private cryptographic key  512  corresponds to a user of the voice communication device. 
     Block hashing process  500  adds hashed value  510  of block 1  502  to block 2  504 . Then, block hashing process  500  again utilizes hashing algorithm  508  to generate hashed value  514  of block 2  504 , which also now includes hashed value  510  of block 1  502 , based on private cryptographic key  512 . Block hashing process  500  then adds hashed value  514  of block 1  502  and block 2  504  to block 3  506 . Block hashing process  500  continues to add a hashed value of a predecessor block, which includes a hashed value of its immediate predecessor, to a next or successor block until block hashing process  500  reaches an end of the segmented audio stream (e.g., end of the call). 
     With reference now to  FIG.  6   , a diagram illustrating an example of a real time audio stream validation process is depicted in accordance with an illustrative embodiment. Real time audio stream validation process  600  may be implemented in a network of data processing systems, such as, for example, network data processing system  100  in  FIG.  1   . 
     In this example, real time audio stream validation process  600  includes calling device  602  and called device  604 . Calling device  602  and called device  604  may be, for example, client  110  and client  112  in  FIG.  1   , respectively. Calling device  602  is a first voice communication device sending an audio stream, such as, for example, audio stream  300  in  FIG.  3   , of a voice communication corresponding to a call. Called device  604  is a second voice communication device, which is to receive the audio stream of the voice communication corresponding to the call from calling device  602 . 
     Also, real time audio stream validation process  600  includes initiate call phase  606 , during call phase  608 , and end call phase  610 . Initiate call phase  606  represents when calling device  602  is connecting to called device  604  via a network, such as, for example, network  102  in  FIG.  1   . During call phase  608  represents when users of calling device  602  and called device  604  are engaged in voice communication (e.g., a spoken conversation). End call phase  610  represents when the network connection is terminated between calling device  602  and called device  604 . 
     At  612 , calling device  602  initiates the call to called device  604 . At  614 , calling device  602  loads a private cryptographic key corresponding to the user (i.e., caller) of calling device  602 . The private cryptographic key corresponding to the user may be, for example, private cryptographic key  512  in  FIG.  5   . At  616 , the user of called device  604  answers the call. At  618 , called device  604  identifies the caller ID corresponding to calling device  602  and loads the public cryptographic key corresponding to the user of calling device  602 . It should be noted that calling device  602  and called device  604  already exchanged private/public cryptographic key pairs. 
     At  620 , calling device  602  starts to receive the audio stream of the voice communication from the user of calling device  602 . At  622 , calling device  602  segments the audio stream into a series of blocks to form a segmented audio stream, such as, for example, segmented audio stream  400  in  FIG.  4   . At  624 , calling device  602  generates a hashed value of a current block of the audio stream, such as, for example, hashed value  510  of block 1  502  in  FIG.  5   . Calling device  602  generates the hashed value of the current block based on the loaded private cryptographic key corresponding to the user of calling device  602  using a hashing algorithm, such as, for example, hashing algorithm  508  in  FIG.  5   . 
     At  626 , calling device  602  sends the current block of the audio stream of the voice communication corresponding to the call with a hashed value of a previous block to called device  604 . Calling device  602  can send the hashed value of the previous block via, for example, a high frequency signal integrated within the audio stream. At  628 , called device  604  receives the current block of the audio stream with the hashed value of the previous block from calling device  602  via the network. At  630 , called device  604  verifies that the hashed value of the previous block is valid using the loaded public cryptographic key related to the private cryptographic key corresponding to the user of calling device  602 . 
     At  632 , called device  604  makes a determination as to whether the hashed value of the previous block is valid based on the verification at  630 . If called device  604  determines that the hashed value of the previous block is invalid, then, at  634 , called device  604  alerts the user of called device  604  regarding the invalid block of the audio stream via, for example, a screen notification or pop-up. In addition, at  636 , called device  604  ends the call (e.g., terminates the network connection) with calling device  602 . 
     However, if called device  604  determines that the hashed value of the previous block is valid, then, at  638 , called device  604  makes a determination as to whether the call has ended. If called device  604  determines that the call has ended, then, at  640 , called device  604  ends the call by terminating the network connection. If called device  604  determines that the call has not ended, then called device  604  continues to receive the audio stream with a hashed value of previous blocks. 
     Further, in addition to calling device  602  sending the current block of the audio stream with the hashed value of the previous block at  626 , calling device  602 , at  642 , processes the next block in the audio stream as the current block. At  644 , calling device  602  adds the hashed value of the previous or predecessor block to the current block. Then, real time audio stream validation process  600  goes from  644  back to step  624  where calling device  602  generates a hashed value of the current block, which now contains the hashed value of the previous block. 
     With reference now to  FIG.  7   , a flowchart illustrating a process for validating hashed audio stream blocks in real time is shown in accordance with an illustrative embodiment. The process shown in  FIG.  7    may be implemented in a first voice communication device, such as, for example, client  110  in  FIG.  1    or data processing system  200  in  FIG.  2   . For example, the process shown in  FIG.  7    may be implemented in audio stream validator  218  in  FIG.  2   . 
     The process begins when the first voice communication device segments an audio stream of a voice communication corresponding to a call to a second voice communication device into a plurality of blocks in response to the first voice communication device receiving the audio stream from a user of the first voice communication device (step  702 ). The second voice communication device may be, for example, client  112  in  FIG.  1   . The segmented audio stream may be, for example, segmented audio stream  400  in  FIG.  4   . 
     The first voice communication device modifies the plurality of blocks to generate a first modified audio stream corresponding to the call that includes hashed values of the plurality of blocks (step  704 ). It should be noted that the first voice communication device modifies the plurality of blocks to generate the first modified audio stream corresponding to the call by performing the process shown in  FIG.  8   . The first voice communication device sends the first modified audio stream along with the hashed values of the plurality of blocks to the second voice communication device via a network (step  706 ). The network may be, for example, network  102  in  FIG.  1   . 
     Subsequently, the first voice communication device receives a block with a hashed value of a previous block of a second modified audio stream corresponding to the call from the second voice communication device via the network (step  708 ). The first voice communication device validates whether the hashed value received with the second modified audio stream from the second voice communication device was generated based on a predetermined cryptographic key corresponding to the second voice communication device using a cryptographic key related to the predetermined cryptographic key (step  710 ). The predetermined cryptographic key may be, for example, a private cryptographic key of a private/public cryptographic key pair. The cryptographic key related to the predetermined cryptographic key may be, for example, a public cryptographic key of the private/public cryptographic key pair. 
     The first voice communication device makes a determination as to whether the hashed value received with the second modified audio stream is valid based on the validation performed in step  710  (step  712 ). If the first voice communication device determines that the hashed value received with the second modified audio stream is not valid, no output of step  712 , then the first voice communication device alerts the user that the hashed value is invalid (step  714 ). In addition, the first voice communication device terminates the call (step  716 ). Thereafter, the process terminates. 
     Returning again to step  712 , if the first voice communication device determines that the hashed value received with the second modified audio stream is valid, yes output of step  712 , then the first voice communication device permits the call to proceed (step  718 ). Further, the first voice communication device makes a determination as to whether the call ended (step  720 ). If the first voice communication device determines that the call has not ended, no output of step  720 , then the process returns to step  708  where the first voice communication device waits to receive another block with a hashed value of previous blocks of the second modified audio stream. If the first voice communication device determines that the call has ended, yes output of step  720 , then the process terminates thereafter. 
     With reference now to  FIG.  8   , a flowchart illustrating a process for hashing blocks of an audio stream is shown in accordance with an illustrative embodiment. The process shown in  FIG.  8    may be implemented in a voice communication device, such as, for example, client  110  in  FIG.  1    or data processing system  200  in  FIG.  2   . For example, the process shown in  FIG.  8    may be implemented in audio stream validator  218  in  FIG.  2   . 
     The process begins when the voice communication device generates a hashed value for a first block of a plurality of blocks in a series comprising an audio stream of a voice communication corresponding to a call using a predetermined cryptographic key corresponding to a user of the first communication device (step  802 ). The predetermined cryptographic key corresponding to the user may be, for example, a private cryptographic key of a private/public cryptographic key pair corresponding to the user. The voice communication device adds a hashed value associated with a predecessor block to a respective successor block for each successor block in the plurality of blocks in the series (step  804 ). The voice communication device generates a hashed value for the respective successor block that includes the hashed value associated with the predecessor block (step  806 ). Thereafter, the process terminates. 
     Thus, illustrative embodiments of the present invention provide a computer-implemented method, computer system, and computer program product for validating that an audio stream of a voice communication corresponding to a call is authentic from a trusted source and has not been tampered with by verifying a hashed value of each respective block in a series of blocks comprising the audio stream. The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.