Abstract:
A method for selectively encrypting electronically communicated information including the steps of: in a first mode, allowing audio and facsimile signals to pass between communications devices in a substantially unaltered manner; in a second mode: establishing a secure session between a first security device and a second security devices; intercepting and digitizing audio signals to produce audio data; encrypting the audio data; and, modulating the encrypted audio data for transmission over the secure session; and, in a third mode: automatically intercepting a signal indicative of an attempt to transmit or receive a facsimile; establishing a facsimile session dependent upon at least one characteristic indicative of a rate at which information can be transmitted and received using the secure session; receiving facsimile signals and demodulating the received facsimile signals to produce facsimile data; encrypting the facsimile data; and, modulating the encrypted facsimile data for transmission over the secure session.

Description:
FIELD OF THE INVENTION 
     The present invention relates to telecommunications security devices, and more particularly to a security device adapted for use with audible, facsimile and data transmissions. 
     BACKGROUND OF THE INVENTION 
     As the demand for increased security of telecommunications systems grows, so that unauthorized interception of audible, data, facsimile and other electronically transmitted information is minimized, so does the need for devices capable of satisfying these demands. 
     For example, a potential user may telecommute from a home office and use voice, computerized data and facsimile communications. Therefore, it is desirable to have some way for securing each communication of these types, to prevent or at least impede unauthorized access thereto. 
     If the telecommuting user telephones a second user, and in the course of their discussions decides to discuss sensitive information, he may wish to encrypt information in an attempt to frustrate unauthorized interception thereof. Further, in the course of the conversation he may wish to send or receive a facsimile. Further yet, it may be desirable that this facsimile also be encrypted. Therefore, it is desirable that the ability be provided to send and/or receive facsimile transmissions without being required to terminate the telephone call and initiate a new call. 
     Further yet, it is also desirable to permit the transfer of at least one computer file between the users, in such case it may again desirable to be able to encrypt the same and not require the users to initiate a new communications session, but rather just continue the original session. 
     Finally, as many users already possess telephones, facsimile machines and computers, it is desirable to provide a security device capable of performing these functions in connection with these existing devices. 
     Accordingly, it is an object of the present invention to provide a device capable of enabling encrypted and non-encrypted voice, data and facsimile transmission during a single communications session, without requiring a user thereof to commence a separate communications session. 
     It is a further object to provide a device capable of permitting simultaneous, fax and/or full-duplex voice transmissions with data transmissions in a secured manner. 
     SUMMARY OF THE INVENTION 
     A method for selectively encrypting electronically communicated information including the steps of: in a first mode, allowing audio and facsimile signals to pass between communications devices in a substantially unaltered manner; in a second mode: establishing a secure session between a first security device and a second security devices; intercepting and digitizing audio signals to produce audio data; encrypting the audio data; and, modulating the encrypted audio data for transmission over the secure session; and, in a third mode: automatically intercepting a signal indicative of an attempt to transmit or receive a facsimile; establishing a facsimile session dependent upon at least one characteristic indicative of a rate at which information can be transmitted and received using the secure session; receiving facsimile signals and demodulating the received facsimile signals to produce facsimile data; encrypting the facsimile data; and, modulating the encrypted facsimile data for transmission over the secure session. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 illustrates an overview of a communications system according to the present invention. 
     FIG. 2 illustrates a block diagram of a telecommunications security device according to the instant invention. 
     FIG. 3 illustrates an overview of operation of the security device of FIG. 2 according to the instant invention. 
     FIG. 4 illustrates a first operations flow diagram according to the instant invention. 
     FIG. 5 illustrates a second operations flow diagram according to the instant invention. 
     FIG. 6 illustrates a third operations flow diagram according to the instant invention. 
     FIG. 7 illustrates a fourth operations flow diagram according to the instant invention. 
     FIG. 8 illustrates a fifth operations flow diagram according to the instant invention. 
     FIG. 9 illustrates a sixth operations flow diagram according to the instant invention. 
     FIG. 10 illustrates a seventh operations flow diagram according to the instant invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the numerous figures, wherein like references refer to like elements and steps according to the instant invention, FIG. 1 illustrates a telecommunications system configuration which includes security devices  10 ,  10 ′ according to the instant invention. For sake of explanation, the following discussion will utilize a prime (′) description for those elements and steps relating to a second like device. 
     Therein a first user at a first location  50  has access for example to a first security device  10 , telephone  20 , facsimile machine  30  and computer  40 . The second user at a location  50 ′ has access to a second security device  10 ′, telephone  20 ′, facsimile machine  30 ′ and computer  40 ′. The first user&#39;s devices ( 10 ,  20 ,  30 ,  40 ) can be interconnected to the second user&#39;s devices ( 10 ′,  20 ′,  30 ′,  40 ′) using any conventional communications system  60 , for example a conventional public switched telephone network (“PSTN”). Alternatives for a PSTN include the Internet for example or any other suitable configuration, i.e. wireless for example. 
     As set forth, it is desirable that the first user and second user, in a single communications session, be able to communicate in both encrypted and non-encrypted modes over the telephones  10  and  10 ′, transmit and receive documents either in an encrypted or non-encrypted mode using facsimile machines  30  and  30 ′ and transfer electronic documents, either in an encrypted or non-encrypted mode using the computers  40  and  40 ′. 
     Referring now also to FIG. 2, therein is illustrated a block diagram of a preferred form of the security device  10  according to the instant invention. Preferably the device  10  includes at least three input/output (I/O) ports. These include a line port  70 , phone port  80  and data port  90 . Alternatively, an additional phone port could be provided for purposes of providing separate facsimile and voice ports to further permit multiplexing voice and fax information as will be discussed further. The line and phone ports ( 70 ,  80 ) are preferably standard RJ-11 type ports, however other configurations may be adopted to complement the choice of communications system  60  and devices  20 ,  30 ,  40 . The line port  70  is preferably coupled to the communications network  60 , while the phone port  80  is preferably coupled to a telephone  20  and/or facsimile machine  30  (depending upon what devices  20 ,  30  are available and whether a separate port has been provided for facsimile machine  30  for example). 
     The data port  90  preferably takes the form of a serial I/O port, i.e. RS-232, which is adapted to permit direct communications between the computer  40  and security device  10  for example. It should be recognized though that the choice of data port  90  to be an RS-232 type port further permits for the security device  10  to be electronically coupled to any device capable of communicating with it there over, for example virtually any computer, personal data assistant or other proprietary device adapted to communicate over an RS-232 interface. However, other suitable interfaces can of course be utilized (wireless for example). 
     The device  10  preferably incorporates two (2) modems  100  and  110  each coupled to the telephone interface  160 , at least one of which is preferably at least 56K and v.90 compatible as is understood by those skilled in the art (preferably  110 ). Obviously, the faster and more reliably these modems can perform, the better overall system performance will be. Modem  100  is adapted to communicate with a device attached to the phone port  80 , i.e. facsimile machine  30 , while modem  110  is adapted to communicate with a counterpart modem  110 ′ of a second security device (i.e.  10 ′). 
     The device  10  preferably further includes a microcontroller  120  coupled to the modems  100 ,  110 , data port  90 , encryption/decryption device  130 , digital signal processor (“DSP”)  140 , audio codec  150 , telephone interface  160 , SRAM  170  and program memory  180 . Preferably the microcontroller  120  serves to control and pas data to and from these elements, as is well known for example. The microcontroller  120  preferably also performs multiplexing of data from separate sources (i.e. fax/data/voice). 
     Preferably the digital signal processor (“DSP”)  140  serves to generate encryption/decryption codes. 
     Preferably, the encryption/decryption device  140  serves to encrypt and decrypt data consistent with these encryption/decryption codes as is well known, and is preferably coupled to a EEPROM  190  to facilitate this purpose. The program memory  180  preferably stores the microcontroller&#39;s  120  program and the SRAM  170  serves as a memory unit for operation of the microcontroller. 
     Preferably the microcontroller  120  takes the form of a model INTEL N80L2515Q16 and the DSP  140  takes the form of a model TI TM5320L542P6-40. As is well known the modems  100 ,  110  utilize ROMs  102 ,  112  and SRAMs  104 ,  114  which may either be internal or external to the modems  100 ,  110  as is known. 
     Referring now also to FIG. 3, preferably upon initial connection to one another, two devices (i.e.  10  and  10 ′) enter a non-encrypted (“plaintext”) mode, after which a user may switch over to encrypted (“ciphertext”) mode. It should be recognized in the preferred embodiment of the present invention, it doesn&#39;t matter which device  10 ,  10 ′ initiates a request to enter ciphertext mode, thus permitting one of the devices  10 ,  10 ′ to operate unattended by receiving an indication of a request to enter ciphertext mode from the other attended device  10 ,  10 ′. 
     Each device  10 ,  10 ′ preferably enters a standby, on-hook mode (i.e.  200 ,  200 ′) until an off-hook condition or ring in is detected. Thereafter each device  10 ,  10 ′ preferably and respectively enters a plaintext voice mode (i.e.  200 ,  200 ′). In that mode audio and facsimile communications pass through the devices  10  and  10 ′ without any change thereto. If computer or proprietary data is to be transmitted in the clear, i.e. without encryption, the devices  10 ,  10 ′ preferably and respectively enter a plaintext data mode  220 ,  220 ′. If the users of the devices  10 ,  10 ′ wish to secure communication between them, the devices preferably and respectively enter a ciphertext voice mode  230 ,  230 ′. If the users wish to transfer data in an encrypted format the devices preferably and respectively enter a ciphertext data mode  240 ,  240 ′. Finally, if the users want to share a secured facsimile transmission the devices  10 ,  10 ′ preferably and respectively enter ciphertext fax modes  250 ,  250 ′. 
     For sake of clarity, a preferred form of the invention will now be described with reference to a communications session between two users, although it is to be understood that the present disclosure of the preferred form has been made only by way of example, and that numerous changes in the details of construction and combination and arrangement of parts may be made without departing from the spirit and scope of the invention 
     Plaintext Mode 
     Voice, facsimile and data transfer modes (i.e. computer-to-computer) are all preferably available in plaintext mode. In plaintext voice mode, the first user is, for example, using the telephone  20  to communicate with another telephone (i.e.  20 ′). Essentially, the ports  70  and  80  are coupled together, allowing the device  10  to appear transparent to the users. While in plaintext voice mode, either user may instruct his respectively associated device  10  that he wishes to enter the ciphertext mode, for example by activating or pressing a button on the device  10 . Thereafter, the device  10 ,  10 ′ which was directly instructed to enter ciphertext mode by a user can signal the other device  10 ,  10 ′ to in turn enter ciphertext mode using conventional methodology. Alternatively, both user may respectfully instruct their respectively associated device  10 ,  10 ′ that they wish to enter the ciphertext mode, for example by each activating or pressing a button on their respective device  10 ,  10 ′. 
     Either way, responsively thereto the devices  10  and  10 ′ will exchange keys as will be discussed and enter the ciphertext mode as set forth below. If a modem request is received via the data port  90 , the modem  110  is preferably further adapted to operate as a standard external computer modem using the port  70  for the device initiating the request via the data port  90 . In other words, it is operable as a standard external modem for a computer  40  for enabling it to contact other computers or connect to the Internet for example. 
     Similarly, the facsimile machine  30  can communicate through the communications system  60  via the ports  70  and  80  and the computer  40  could alternatively communicate using an internal facsimile and/or modem card though the communications system  60  via the ports  70  and  80  for example. 
     Referring now to FIG. 4, therein is disclosed a flow diagram according to a preferred form of the present invention which first illustrates a phone-on hook, or stand-by mode  200 . The device  10 , for example by monitoring a line voltage, can determine whether the phone line coupled through ports  70  and  80  is on or off hook, as is well known to those possessing ordinary skill in the art. When the phone goes off-hook, for example when a user lifts the handset of telephone  20  or a facsimile session is attempted to be commenced using facsimile machine  30 , the device detects this and proceeds to enter an off-hook status/plaintext voice mode  260 . 
     On the reverse end of the call commenced using the device  10 , or receiving end, device  10 ′ identifies a ring-in condition upon an incoming call, again for example by monitoring the line voltage as is well known. If the call terminates without a connection the device  10  (originating) senses that the phone is on-hook again and returns to on-hook default or standby mode  200  and device  10 ′ detects ring-in end and also returns itself to on-hook default mode  200 . 
     Alternatively, if the incoming call is picked up by a user, the device  10 ′ detects the off-hook condition and enters an off-hook plaintext voice mode  260 ′. A plaintext voice mode is now commenced for example, as the originating device  10  is in plaintext voice mode  260  and the destination device  10 ′ is in plaintext voice mode  260 ′. In this plaintext voice mode  260  for the originating device  10  and  260 ′ for the destination device  10 ′, either device  10  or  10 ′ can send or receive a data file via the data ports  90 ,  90 ′. 
     Referring now also to FIG. 5, for sake of example, if the user of the device  10  wishes to transmit a file from the computer  40  to the computer  40 ′, the device  10  receives an instruction, i.e. modem request, through the data port  90  and enters a plaintext data setup mode  270 , wherein modem  110  thereof would couple to the line port  70 , the audio codec  150  couples to the phone port  80  for reasons as will be set forth later and data is directed between the modem  110  and data port  90  by the microcontroller  120 . Alternatively, a driver operating on the computer  40  could be used to direct interaction between the device  10  and computer  40  consistently with conventional methods. 
     In turn the device  10 ′ detects a receive file command, either from the user thereof through the port  90 ′ or upon indication thereof from the device  10 , and enters a plaintext data setup mode  270 ′, wherein modem  110 ′ thereof couples to the line port  70 ′, the audio codec  150 ′ couples to the phone port  80 ′ for reasons as will be set forth later and data is transmitted between the modem  110 ′ and data port  90 ′. 
     Thereafter, device  10  enters a data transmit mode  280  and device  10 ′ enters data receive mode  290 ′ wherein a file is transmitted from computer  40 , through port  90 , into device  10 , to modem  110 , through telephone interface  160  out port  70 , into port  70 ′, through telephone interface  160 ′ to modem  110 ′, out port  90 ′ and into computer  40 ′. After the file transfer is complete, the devices  10 ,  10 ′ preferably return to plaintext voice modes  260 ,  260 ′. 
     Of course, a file could be transmitted from computer  40 ′ to computer  40  in the same manner, i.e. device  10 , going into plaintext data transmit mode  280 ′ and device  10  going into plaintext data receive mode  290  and eventually back to plaintext voice modes  260  and  260 ′. 
     Alternatively, a user may wish to send a plaintext facsimile, in such case the modems of the facsimile machines  30  and  30 ′ preferably negotiate a communications session therebetween and transmit the document as is well known. It should be noted that the devices  10  and  10 ′ remain transparent to the facsimile machines  30  and  30 ′ and hence the users thereof in the plaintext mode. Hence, in plaintext mode, the users of the devices continue to operate telephones  20 ,  20 ′, facsimile machines  30 ,  30 ′ and computers  40  and  40 ′ conventionally, which of course makes the devices  10 ,  10 ′ easier to use. 
     When the users select to end their conversation, they simply hang up the telephones and both devices detect an on-hook condition and return to on-hook standby mode  200 ,  200 ′ for example. 
     Cirhertext Mode 
     As set forth, in the plaintext voice mode  160 ,  260 ′ either or both users can instruct the devices  10 ,  10 ′ that he wishes to enter a secured or ciphertext mode by pressing a button on his respectively associated device  10  or  10 ′ for example. It should be recognized that the device  10  could further be adapted to monitor voice, facsimile and data transmissions in the plaintext mode for instructions to convert over to the ciphertext mode, the drawbacks of such a configuration however include that it requires the device  10  monitor the line in case the other device  10 ′ attempts to convert over to ciphertext mode during facsimile or data transmissions, which in turn requires more complex circuitry and programming. Alternatively, the device  10  could begin, or default in ciphertext mode upon commencement of a communications session with a second user also utilizing a security device according to the present invention, i.e. device  10 ′. 
     Referring now to FIG. 6, and again to the communication session as discussed regarding plaintext voice mode and FIG. 4, once the users have connected the devices  10  and  10 ′ in the plaintext voice modes  260  and  260 ′ as has been set forth, they may wish to commence secured operation, for example by at least one user pressing a button to which the devices  10  and  10 ′ are instructed to enter a ciphertext, or secured operation mode. 
     Upon indication that the user wants to enter ciphertext mode, the device  10  enters a ciphertext setup mode  300  wherein the phone port  80  is coupled to the audio codec  150 , modem  110  is coupled to the line port  70  to facilitate connection thereof with device  10 ′ and modem  100  monitors the phone port  80 . Similarly, device  10 ′ enters ciphertext setup mode  300 ′ wherein the phone port  80 ′ is coupled to the audio codec  150 ′, modem  110 ′ is coupled to the line port  70 ′ to facilitate connection thereof with device  10  and modem  100 ′ monitors the phone port  80 ′. 
     After these steps have been performed, the modems  110 ,  110 ′ of the security devices  10 ,  10 ′ negotiate a protocol to be used for communications there between using conventional techniques as is well known  310 . After the modems  110 ,  110 ′ have negotiated a protocol for a secured session which is commenced between them, the capabilities of this secured session are preferably reported to each microcontroller  120 ,  120 ′ by the respectively modem  110 ,  110 ′. Each microcontroller  120 ,  120 ′ preferably then, determines the capabilities of the secured communications session commenced  320  and directs  330  the mode of operation of the modem  100 ,  100 ′ and audio codecs  150 ,  150 ′. Each modem  100 ,  110 ′ and audio codec  150 ,  150 ′ can be controlled to operate in different modes as is well known. For example, the speed at which each modem  100 ,  100 ′ operates is controllable, as is a level of quality for the audio codecs  150 ,  150 ′. Preferably, the higher the capabilities of the secured session (i.e. higher the speed, better error correction) the faster the modems  100 ,  100 ′ can operate and the higher the level of quality the audio codecs can be operated in. Preferably for example, if a 33.6 Kbps connection can be established for the secure session, the modems  100 ,  100 ′ can operate at up to 14.4 Kbps and the audio codecs  140 ,  140 ′ can be operated in their highest level of quality. However, if a slower connection is established for the secure session between the devices  10 ,  10 ′, the modems  100 ,  100 ′ are preferably operated in a slower mode (i.e. 9600 bps) and the quality of the codecs  150 ,  150 ′ performance is diminished to reflect the limited capabilities of the secure session. 
     Encrypt/decrypt devices  130 ,  130 ′ of the devices  10 ,  10 ′ preferably exchange keys to permit for secured communications between the devices  10 ,  10 ′ after a session protocol has been negotiated (illustrated in element  310 ). Referring again to FIG. 1, using such a configuration allows for all communications occurring over the communications system  60 , i.e. between the users locations  50 ,  50 ′, to be encrypted to prevent, or at least impede unauthorized interception therefrom. 
     After these steps have been performed, the device  10  enters ciphertext voice mode  340  and device  10 ′ enters corresponding ciphertext voice mode  340 ′. As set forth, if an on-hook detection is made by either device  10 ,  10 ′, eventually both devices  10 ′  10 ′ are returned to on-hook standby mode  200 . Alternatively, either, or both users may opt to return to plaintext voice modes  260 ,  260 ′. In such a case, for example by activating the same button as for entering ciphertext mode, a user can instruct the device to return to plaintext voice mode  260 ,  260 ′. 
     Referring now also to FIG. 7, in the ciphertext voice mode ( 300 ,  300 ′) voice communications from telephone  20  are, for example, received by the device  10  through port  80  and fed through the telephone interface  160  to the audio codec  150  for digitization, the digitized voice is then directed by the microcontroller  120  to the encrypt/decrypt device  130  which encrypts the digitized voice consistently with the keys which have been exchanged between the devices  10  and  10 ′ previously. This encrypted data is then directed by the microcontroller  120  to the modem  110  and through telephone interface  160  to line port  70  for transmission across communications system  60  to device  10 ′. In turn, device  10 ′ receives the transmitted, encrypted, digitized voice signal through port  70 ′, telephone interface  160 ′ and modem  110 ′. This encrypted, digitized voice signal is then directed by the microcontroller  120 ′ to the encrypt/decrypt device  130 ′ which decrypts it consistent with the key which has been generated and exchanged. The decrypted digitized voice signal is then directed by the microcontroller  120 ′ to the audio codec  150 ′ which un-digitizes it, or converts the signal to a conventional analog telephone signal which is in turn fed to the telephone interface  160 ′ and phone port  80 ′. The signal can then be heard by a user utilizing telephone  20 ′. Encrypted voice communications from telephone  20 ′ to telephone  20  are conducted in a reverse direction but identical manner. 
     Referring now also to FIG. 7, in the ciphertext mode  340 ,  340 ′ either computer  40  or  40 ′ can preferably send or receive a data file via the respective data port  90 ,  90 ′. For sake of example, and referring again to the same communications session between a user of device  10  and a user of device  10 ′, if the user of the device  10  wishes to transmit a file from the computer  40  to the computer  40 ′, the device  10  receives an instruction from the data port  90  and enters a ciphertext data setup mode  350 , wherein modem  110  maintains the secure session over the line port  70 , the audio codec  150  couples to the phone port  80  for reasons as will be set forth later and data is transmitted between the modem  110  and data port  90 . 
     Likewise, the device  10 ′ detects a modem request, either from the user thereof or from the device  10  for example, and enters a ciphertext data setup mode  350 ′, wherein modem  110  also maintains the secure session over line port  70 ′, the audio codec  150 ′ couples to the phone port  80 ′ for reasons as will be set forth later and data is transmitted between the modem  110 ′ and data port  90 ′. 
     Thereafter, device  10  enters a ciphertext data transmit mode  360  and device  10 ′ enters ciphertext data receive mode  370 ′. Therein, a file is transmitted from computer  40  through port  90  into device  10 , directed by the microcontroller  120  to the encrypt/decrypt device  130  for encryption consistent with the previously negotiated security key, modulated by modem  110  and transmitted through telephone interface  160  out port  70  to the communications system  60 . The data is then received by the device  10 ′ using port  70 ′ and telephone interface  160 ′, demodulated by modem  110 ′, and directed by microncontroller  120 ′ to the encrypt/decrypt device  130 ′ for decryption. The decrypted data is then directed out port  90 ′ by the microcontroller  120 ′ and into computer  40 ′. After the file transfer is complete, the devices preferably return to ciphertext voice modes  340  and  340 ′. 
     Of course, a file could be transmitted from computer  40 ′ to computer  40  in a reverse direction but identical manner. However, it should be understood that one cannot simply transmit a facsimile between facsimile machines  30 ,  30 ′ in ciphertext, or encrypted mode such as was done in plaintext mode, as a secured session has already been commenced over the communications system  60  for example, hence rendering it impossible to simultaneously commence a conventional facsimile protocol session thereover. 
     Therefore, and referring now also to FIG. 8, to conduct encrypted facsimile transmissions between facsimile machines  30 ,  30 ′ the devices  10 ,  10 ′ have their modems  100 ,  100 ′ respectively coupled to the phone ports  80 ,  80 ′. These modems  100 ,  100 ′ respectively monitor signals received at ports  80 ,  80 ′ for at least one standard facsimile signal (i.e. DIS signal). Upon detection of a facsimile signal, the modems  100 ,  100 ′ respectively negotiate a standard session with the locally connected facsimile machine  30 ,  30 ′ consistent with the capabilities of the secured session as has been set forth. 
     As is well known modems  100 ,  100 ′ can be configured to respectively provide an output signal to the microcontrollers  120 ,  120 ′ upon detection of a standard facsimile transmit or receive signal (i.e. DIS signal). Upon receipt of one of these signals, preferably the receive facsimile signal, one device  10 ,  10 ′ can be configured to transmit this status to the other device  10 ,  10 ′. 
     For example, and referring again to the same communication session as has been described with regard to plaintext and ciphertext voice communications, the users of the devices  10 ,  10 ′ may wish to transmit a document from facsimile machine  30  to facsimile machine  30 ′ in an encrypted manner. To effectuate such a transmission, the users may agree to do such, and a document placed into facsimile machine  30  and a start button activated thereon for example. On the other end, a start button may also be activated on the facsimile machine  30 ′ which has had no document previously placed into its page feeder as it is intended to receive the document from facsimile machine  30 . 
     It should be understood that conventionally at this point facsimile machines  30  and  30 ′ would negotiate a communications session over communications system  60  for transmitting the document placed in the sheet feeder of the facsimile machine  30 . However, due to the secure communications session already in place between modems  110 ,  110 ′ of the devices  10 ,  10 ′ over communications system  60  such is not feasible using conventional facsimile technology. 
     When the document was placed in facsimile machine  30  and the start button activated, a signal attempting to commence a facsimile session was transmitted by the facsimile machine  30  and received by the device  10  through phone port  80 . This signal is indicative of attempting to transmit a facsimile document. Because modem  100  is monitoring the phone port  80 , as has been set forth, it can detect this signal and in turn signal the microprocessor  120 . Similarly, when the send button is activated on the facsimile machine  30 ′ a signal attempting to commence a facsimile session was transmitted by the facsimile machine  30 ′ and received by the device  10 ′ through phone port  80 ′. This signal is indicative of an attempt to receive a facsimile document. Because modems  100 ,  100 ′ are monitoring the phone ports  80 ,  80 ′, as has been set forth, they can individually detect these signals. 
     Upon either unit detecting one of these signals, but preferably the receiving unit, i.e.  10 ′ in this example, a control signal can be passed over the communication session between modems  110 ,  110 ′ of devices  10 ,  10 ′ such that the microcontrollers  120 ,  120 ′ can direct the devices  10 ,  10 ′ to enter ciphertext facsimile mode. 
     Upon such a direction the device  10  enters ciphertext facsimile setup mode  380 . Therein, the phone port  80  is coupled to modem  100 , the secure communications session is continued using modem  110  and the audio codec  150  is preferably uncoupled from phone port  80 ′ if both the fax machine  30  and telephone  20  are coupled to port  80 . Correspondingly, the device  10 ′ enters ciphertext facsimile setup mode  380 ′ wherein phone port  80 ′ is coupled to modem  100 ′, the audio codec  150 ′ is uncoupled from phone port  80 ′ if both the fax machine  30 ′ and telephone  20 ′ are coupled to port  80 ′, and the secure communications session is continued using modem  110 ′. 
     Accordingly, the modem  100  of the device  10  negotiates a facsimile session with facsimile machine  30  and modem  100 ′ of device  10 ′ negotiates a facsimile session with facsimile machine  30 ′, this fax session preferably being consistent with the capabilities of the secure session as determined by the microcontroller  120 . Thereafter, the device  10  enters ciphertext facsimile transmit mode  340  and device  10 ′ enters ciphertext facsimile receive mode  400 ′. Therein, data is transmitted from the facsimile machine  30  to modem  100  of the device  10  through phone port  80  and telephone interface  160 . This data is demodulated by the modem  100  of the device  10  and directed by the microcontroller  120  to encrypt/decrypt device  130  which encrypts the data consistent with the security key previously negotiated between the devices  10 ,  10 ′. This encrypted data is then directed by the microcontroller  120  to the modem  110  and transmitted out line port  70  through telephone interface  160  to the communications system  60 . The encrypted data is received by the device  10 ′ from the communications system  60  through the port  70 ′ and telephone interface  160 ′, demodulated using modem  110 ′ and directed by the microcontroller  120 ′ to the encrypt/decrypt device  130 ′ which decrypts the data consistent with the key previously negotiated between the devices  10 ,  10 ′. The microcontroller  120 ′ then directs the decrypted data to the modem  100 ′ which modulates the data consistent with the session commenced between it and the facsimile machine  30 ′. The modulated data is then sent to phone port  80 ′ though the telephone interface  160 ′ to the facsimile machine  30 ′ where it is received. After the facsimile transmission is complete the devices  10 ,  10 ′ preferably returns to ciphertext voice modes  340 .,  340 ′. 
     Advantageously, this all appears transparent to the users who only see facsimile machine  30  transmitting a facsimile document and facsimile machine  30 ′ receiving a facsimile document. Of course, a facsimile document could be sent from facsimile machine  30 ′ to facsimile machine  30  in the reverse but identical manner. 
     Use with Proprietary Hardware 
     The use of proprietary herein is meant to indicate any electronic device adapted to communicate over communications system  60 . As set forth the device  10  preferably incorporates a standard format data port  90 . In the preferred form this takes the form of an RS-232 type port. As stated, an advantage of incorporating such a standard port enables one to utilize the device  10  with any device capable communicating via the standard interface, i.e. in the preferred form RS-232. 
     Accordingly, the device  10  is further capable of being utilized with a variety of proprietary devices, i.e. Personal Data Assistants (PDAs) for example and other electronic devices. One such device is marketed under the tradename Magicom by Copytele, Inc., the assignee hereof. This device permits for handwriting on a pad to be digitized and transmitted to a like Magicom device for display. These Magicom devices preferably use a touch-screen as both a display and input device. 
     Similar as for the computer  40 , a proprietary device is preferably coupled to the device  10  using the data port  90 . A request for service can similarly be received by the device  10  using port  90  and microcontroller  120 . Upon such a request for service, the device  10  handles it consistently as has been set forth for a modem request. 
     Encryption—Key Generation and Exchange 
     Any suitable encryption/decryption device  130 ,  130 ′ can be utilized as is well known in the art. For example, a diffe-hillman public/private key algorithm may be implemented by it. Preferably though, the encryption/decryption device  130  takes the form of a Harris Model No. 10561-1000A. The choice of a hardware encryption device generally results in more robust cryptographic implementation than software alone, generally resulting for example from better random number generation. However, any suitable means for encrypting and decrypting data as is well known in the art can be used. For example, the microcontroller  120  could perform the encryption/decryption software algorithms. 
     Preferably a new session key is generated for each point-to-point real-time communications session using standard public/private key technology and DSP  140 . In other words, for each session the device  10  using the DSP  140  generates a new public/private key combination for use with another like device ( 10 ′) for encrypting and decrypting messages therebetween using conventional techniques. Likewise, the device  10 ′ preferably generates a new public/private key combination. The public portions of these keys are preferably exchanged, and the respective private portion is combined with the received public portion by each encryption/decryption device  130 ,  130 ′ for encrypting and decrypting in according with the present invention. 
     Each device  10  preferably also includes a permanent public/private key combination for non point-to-point transmissions, i.e. over the Internet. In these types of non- real-time transmissions, if the devices  10 ,  10 ′ were to exchange their public/private key as is done for point-to-point transmissions the key would change before the file or other transmission, i.e. E-mail, was recovered and would hence render it unrecoverable, as the devices  10 ,  10 ′ preferably generate a new public/private key combination for each communications session. It should also ve recognized that this feature further permits for file securing within the computer  40  for example by a user sending data to the device  10  and then recovering the encrypted data from it. As the permanent decryption key is available in the device  10  and not the computer  40 , separation of the device  10  from the computer  40  acts as a means of securing data residing in the computer  40 . 
     More particularly, a user, utilizing suitable drivers as is well known to those possessing ordinary skill, could instruct computer  40  to transmit a file to the device  10  for encryption with the permanent key. This encrypted file could then be re-transmitted back to the computer  40 . At this point, using a suitable utility the user could erase the non-encrypted version to prevent unauthorized access to the file. Now that the file is in encrypted format, the user simply needs to follow the same steps with the device, this time instead decrypting the file for access thereto. In this way, even if the computer  40  becomes lost or stolen, unauthorized access to the encrypted file could still be frustrated by adequately safeguarding the device  10 . 
     Further, of course, conventional digital signature technology can be utilized by the devices  10 ,  10 ′ to verify the identity of devices  10 ,  10 ′ and hence their owners or operators. 
     Simultaneous Voice/Facsimile/Data Transmission 
     When operating in a ciphertext mode, it should be noted that only digital data is transmitted between the modems  110 ,  110 ′ of the devices  10 ,  10 ′. For example, in ciphertext voice mode, audio data received from either telephone  20 ,  20 ′ is digitized by the audio codec  140 ,  140 ′. Similarly, in the ciphertext data mode digital data received from the data port  90 ,  90 ′ is transmitted between devices  10 ,  10 ′. Likewise, in the ciphertext facsimile mode, only computerized data (note which is no longer in facsimile format) is transmitted between the devices  10 ,  10 ′. Accordingly, using multiplexing techniques which are well know to those possessing ordinary skill in the art, one can easily simultaneously transmit data, or for example a computer file, between computers  40 ,  40 ′ during facsimile transmission and/or a full-duplex voice conversation, and still encrypt all information (voice and/or facsimile and data). 
     In order to facilitate such, it is necessary to have the audio codecs  150 ,  150 ′ coupled to the respective phone port  80 ,  80 ′ even while data is being transmitted between the data ports  90  and  90 ′. Accordingly, it is also necessary to couple the modems  100 ,  100 ′ to the phone port  80 ,  80 ′ to monitor for a facsimile commencement signals for simultaneous transmission of facsimile data and a computer file for example. 
     In simultaneous modes, headers for each packet can be used, as is well known in the art, to distinguish between data types (i.e. whether the data associated with that particular packet is fax, computer, voice or that of a proprietary device for example). As will be readily understood by those possessing ordinary skill in the pertinent art though, any other suitable form of multiplexing the data could of course be used. 
     Referring now also to FIG. 9, if the device  10  uses a common port  80  for connecting to both the facsimile machine  30  and phone  20 , voice and facsimile signals are received  410  thereon. As the audio codec  150  is decoupled from the phone port  80  when a facsimile signal is detected on the phone port  80 , the microcontroller  120  is capable discerning  420  whether the signal received in step  410  is a facsimile or voice signal. As set forth, if the signal is a voice signal it is digitized  430 . If the signal is a facsimile signal it is demodulated  440  consistent with the session between the fax machine  30  and modem  100  and capabilities of the secure session. Either way, the received signal is fed  450  to the microcontroller  120  for directing. If simultaneously, data is received  460  on the data port  90 , this data is also directed to the microcontroller, wherein it is multiplexed  470  with the data representative of the signal received on the phone port  80  using conventional techniques. This multiplexed data is then directed by the microcontroller  120  to the encrypt/decrypt device  130  for encryption  480  according to the key which was previously negotiated between the devices  10 ,  10 ′. Thereafter, the encrypted multiplexed data is fed to the modem  110  for modulation and transmission  490  across communications system  60  using line port  70 . 
     Referring now also to FIG. 10, the signal is received using the line port  70 ′ and demodulated  500  using modem  110 ′. The data is then fed to the encrypt/decrypt device  130 ′ for decryption  510 . Preferably, a flag within the data itself is read by the microcontroller  120 ′ which indicates to it that the decrypted data includes multiple sources (i.e. is multiplexed)  520 . The data is then de-multiplexed  530  using the microcontroller  120 ′. Data intended for data port  90 ′ is fed thereto  540 . Data intended for phone port  80 ′ must be distinguished  550  into voice and facsimile data, preferably again using a flag for example, or any other suitable means. Voice data is then preferably fed to the audio codec  150 ′ for un-digitization and audible transmission over phone port  80 ′, and fax data is fed to the modem  100 ′ for modulation for transmission over the port  80 ′ to facsimile machine  30 ′. 
     If separate ports are provided within the devices  10 ,  10 ′ for respective connection to facsimile machine  30  and telephone  20 , data from these sources can also me multiplexed, and the audio codecs  150 ,  150 ′ need not be decoupled from the phone ports  80 ,  80 ′ during facsimile transmissions. 
     Although the invention has been described in a preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example, and that numerous changes in the details of construction and combination and arrangement of parts may be made without departing from the spirit and scope of the invention as hereinafter claimed. It is intended that the patent shall cover by suitable expression in the appended claims, whatever features of patentable novelty exist in the invention disclosed.