Internal and external network physical isolation information transmission system and method based on one-way channel

Abstract

The invention relates to an internal and external network physical isolation information transmission system based on a one-way channel. The system comprises a source side external network content host, a source side display capability management module, an audio and video main link sending unit, a one-way transmission link, a decoding and retiming unit and an internal network receiving end, the source side extranet content host comprises a graphics card and a standard audio and video output port, and the standard audio and video output port comprises an audio and video output pin, a display data channel pin, a hot plug detection channel pin and a consumer electronic control pin; the source side extranet content host outputs standard audio and video signals through the audio and video output pin; and the source side extranet content host reads the simulated hot plug detection time sequence signal from the source side display capability management module, expands display identification data and a mode strategy, outputs an audio and video signal in a locking mode, and transmits the audio and video signal to an intranet receiving end through a one-way transmission link. The safety requirements of absolute one-way and physical disconnection can be met.

Description

Technical Field

[0001] This invention relates to the field of information transmission technology, and in particular to a device and method for physical isolation of internal and external networks based on a unidirectional channel. Background Technology

[0002] In the scenario of "internal and external network security isolation", common cross-network data exchange methods include: application layer gateways, protocol stack proxies, file import / export gateways (manual access via USB flash drive / CD), and "data diode" type devices.

[0003] Network gateways rely heavily on protocol parsing and dual-machine isolation, but still have risks such as protocol implementation defects, policy mismatch, and zero-day vulnerabilities; and once the minimum necessary backhaul (such as ACK / retransmission / session control) is opened, a "soft loop" is generated.

[0004] File silos: High labor costs and latency, lacking the ability to publish with "near real-time, stable bandwidth".

[0005] Traditional data diodes are mostly for data leakage protection in the inside-out direction and often run through the Ethernet physical layer / link layer. For "near real-time information dissemination from outside to inside (such as announcements, media, data dashboards, task instruction boards, etc.)," ​​existing general-purpose products are not compatible or require complex protocol / driver adaptation and secondary development.

[0006] Furthermore, taking HDMI as an example, the HDMI protocol and control signals are bidirectional. In actual use, the core "video" signal always flows from the source side (computer host) to the receiving side (display device). However, this unidirectional flow mechanism does not truly rule out the possibility that HDMI could be used as a bidirectional transmission medium, causing the signal on the receiving side to leak to the source side. The reasons are as follows: The HDMI standard link includes: • TMDS (Transition-Minimized Differential Signaling) main data channel (video / audio / auxiliary data, source → display); • DDC / I²C (Display Data Channel; SCL / SDA, Display → Source Interactive Reading of EDID); EDID: Extended Display Identification Data; • HPD (Hot-Plug Detect; Source → Display) • CEC (Consumer Electronics Control; single-wire bus, bidirectional). • 5V power supply and grounding, etc.

[0007] The aforementioned DDC / HPD / CEC essentially form a backhaul / bidirectional control path. Common HDMI optical / electrical extenders also multiplex / forward DDC / CEC / HPD on the optical link for normal handshaking, which is essentially still a "reversible channel" and cannot meet the security requirements of "absolute unidirectional, physical disconnection". Summary of the Invention

[0008] To address the problems in the existing technology, this application proposes a physical isolation information transmission system for internal and external networks based on a unidirectional channel, characterized by comprising: a source-side external network content host, a source-side display capability management module, an audio / video main link sending unit, a unidirectional transmission link, a decoding and retiming unit, and an internal network receiving end; The source-side external network content host includes a graphics card and a standard audio / video output port. The standard audio / video output port includes audio / video output pins, display data channel pins, hot-plug detection channel pins, and consumer electronics control pins. The source-side external network content host outputs standard audio / video signals through the audio / video output pins. The source-side external network content host connects to the source-side display capability management module to read pre-stored signed display capability profiles and simulated hot-plug detection timing signals from the source-side display capability management module. The display capability profile includes extended display identification data and mode policies. The source-side external network content host also outputs audio / video signals in a locked graphics card output mode according to the mode policies. The display data channel pins, hot-plug detection channel pins, and consumer electronics control pins are left unused. The source-side display capability management module is used to return display capability profiles and simulated hot-plug detection timing signals to the source-side external network content host; The audio / video main link transmitting unit is connected to the audio / video output pin to receive audio / video signals and send them to the unidirectional transmission link; A one-way transmission link is used to send the audio and video signals to the decoding and retiming unit; The decoding and retiming unit is used to demodulate the received signal and retime it to a standard audio and video signal. The intranet receiver is used to receive and play standard audio and video signals.

[0009] According to some embodiments of the present invention, the graphics card output mode of the locked source-side external network content host includes fixed resolution and refresh rate, and disables high dynamic range, display stream compression, jitter, scaling and consumer electronics control functions.

[0010] According to some embodiments of the present invention, the standard audio and video output ports include HDMI, VGA, DVI, DP and USB-C output ports.

[0011] According to some embodiments of the present invention, the display data channel pin and the hot-plug detection channel pin are connected to the source-side display capability management module to read pre-stored extended display identification data and simulated hot-plug detection timing signals from the source-side display capability management module, respectively; and the consumer electronics control pin is left unused.

[0012] According to some embodiments of the present invention, the consumer electronics control pins are cut off or sealed.

[0013] According to some embodiments of the present invention, the system further includes a unidirectional transmission link, the unidirectional transmission link comprising: an electro-optical conversion unidirectional optical transmitter for receiving audio and video signals and converting them into optical signals; a unidirectional optical fiber for unidirectionally transmitting the optical signals to an opto-optical conversion unidirectional optical receiver; and an opto-optical conversion unidirectional optical receiver for receiving the optical signals and converting them into electrical signals before outputting them.

[0014] This application also proposes an information transmission method for a physically isolated information transmission system between internal and external networks, characterized by comprising: The source-side external network content host initiates an extended display identifier data read request to the source-side display capability management module; In response to the request, the source-side display capability management module returns a pre-stored signed display capability profile and a simulated hot-plug detection timing signal to the source-side external network content host. The display capability profile includes extended display identification data and mode strategy. The source-side external network content host outputs audio and video signals to the audio and video main link sending unit in the locked graphics card output mode according to the mode policy; The audio / video main link transmission unit receives audio and video signals and sends them to the unidirectional transmission link; The one-way transmission link sends the audio and video signals to the decoding and retiming unit; The decoding and re-timing unit demodulates and re-tims the received signal into a standard audio and video signal; and The intranet receiver receives and plays standard audio and video signals.

[0015] According to some embodiments of the present invention, the standard audio and video output ports include HDMI, VGA, DVI, DP and USB-C output ports.

[0016] According to some embodiments of the present invention, the source-side external network content host reads extended display identification data from the source-side display capability management module through a local I2C bus, wherein the extended display identification data is read-only data.

[0017] According to some embodiments of the present invention, the source-side external network content host reads pre-stored extended display identification data and simulated hot-plug detection timing signals from the source-side display capability management module through the display data channel pin and the hot-plug detection channel pin, respectively; and leaves the consumer electronics control pin idle.

[0018] The following effects can be achieved through this invention: 1. Achieve unidirectional transmission from "outside" to "inside", while physically cutting off all backhaul (DDC / HPD / CEC / covert modulation).

[0019] 2. Under zero backhaul conditions, complete source-side display mode locking (fixed resolution and refresh rate, disable high dynamic range, display stream compression, jitter, scaling and consumer electronics control functions to avoid graphics card "pixel tampering / bandwidth jitter").

[0020] 3. It can help realize a universal, secure, bandwidth-controllable, plug-and-play cross-network information publishing link, while taking into account maintainability and acceptability.

[0021] 4. No need to rebuild complex transmission protocols / driver adaptations and secondary development. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used are briefly described below: Figure 1 An architecture diagram of a physical isolation information transmission system for internal and external networks based on a unidirectional channel, according to some embodiments of the present invention, is shown. Figure 2 This diagram illustrates the signal transmission process on the source side according to some embodiments of the present invention; Figure 3 A schematic flowchart of an information transmission method according to some embodiments of the present invention is shown.

[0023] The correspondence between the reference numerals in the figure is as follows: 100 source-side external network content hosts 110 Source-side Display Capability Management Module 120 Main Link Transmission Unit 130 Electro-optical Conversion Unidirectional Light Emitter 140 unidirectional fiber 150 photoelectric conversion unidirectional light receiver 160 Decoding and Retiming Unit 170 Internal Network Receiver Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0025] Figure 1 An architecture diagram of a system according to some embodiments of the present invention is shown.

[0026] As shown in the figure, the system includes a source-side external network content host 100, a source-side display capability management module 110, a main link sending unit 120, a unidirectional transmission link, a decoding and retiming unit 160, and an internal network receiving end 170.

[0027] According to some embodiments of the present invention, the unidirectional transmission link may include the illustrated electro-optical conversion unidirectional optical transmitter 130, unidirectional optical fiber 140, and photoelectric conversion unidirectional optical receiver 150. The electro-optical conversion unidirectional optical transmitter 130 is used to receive the audio and video signals and convert them into optical signals. The unidirectional optical fiber 140 is used to transmit the optical signals unidirectionally to the photoelectric conversion unidirectional optical receiver. The photoelectric conversion unidirectional optical receiver 150 is used to receive the optical signals, convert them into electrical signals, and output them. In this application, the electro-optical conversion unidirectional optical transmitter can convert electrical signals into optical signals, but cannot convert optical signals into electrical signals; the photoelectric conversion unidirectional optical receiver can convert optical signals into electrical signals, but cannot convert electrical signals into optical signals. The unidirectional transmission link can also be any link that can realize physical unidirectional signal transmission, including but not limited to unidirectional serial cables.

[0028] The source-side external network content host 100 includes a graphics card and a standard audio / video output port. The standard audio / video output port includes audio / video output pins, a display data channel pin (DDC pin), a hot-plug detection channel pin (HPD pin), and a consumer electronics control pin (CEC pin). The source-side external network content host 100 outputs standard audio / video signals through the audio / video output pins. The source-side external network content host is also connected to a source-side display capability management module to read pre-stored signed display capability profiles and simulated hot-plug detection timing signals from the source-side display capability management module. The display capability profile includes extended display identification data and mode strategies. The display data channel pin, hot-plug detection channel pin, and consumer electronics control pin are left unused. In this application, "unused" means that the pin is not connected to any object, and the standard audio / video output port refers to any readily available audio / video output port that can achieve audio / video transmission based on existing protocols.

[0029] According to some embodiments of the present invention, the display data channel pin and hot-plug detection channel pin of the standard audio / video output port are connected to the source-side display capability management module 110 to read pre-stored Extended Display Identifier (EDID) data and simulated hot-plug detection timing signals (simulated HPD timing signals) from the source-side display capability management module 110, respectively, and to keep the consumer electronics control pin idle. Here, the DDC pin in the output port of the source-side external network content host 100 is designed as a local loop-only. The DDC pin is a "handshake" channel. In the prior art, the source-side external network content host normally reads the EDID of the display device through the DDC. However, in the present invention, designing the DDC pin as a "local loop-only" means that the DDC pin is designed to connect only to the source-side display capability management module, preventing the source-side external network content host 100 from reading the actual EDID of the display device on the remote receiving side, and instead reading a copy of the EDID that it "forges" locally. When the source-side external network content host 100 attempts to read the signal through DDC, the DDC handshake is "intercepted" and the source-side display capability management module 110 locally replies with its pre-stored (or forged) EDID.

[0030] The source-side display capability management module 110 is used to return display capability profiles and simulated hot-plug detection timing signals to the source-side external network content host. The display capability profile includes extended display identifier data and mode policies. The mode policies are used to lock the graphics card output mode of the source-side external network content host to prevent graphics card bandwidth / pixel side channel jitter. Locking the graphics card output mode of the source-side external network content host includes fixing the resolution and refresh rate, and disabling high dynamic range, display stream compression, jitter, scaling, and consumer electronics control functions. Other factors that may affect the graphics card output mode are also within the scope of disabling in this application; however, since it is impossible to list them all, the most common ones are selected here. The source-side display capability management module 110 may include policy firmware to implement the aforementioned functions.

[0031] According to some embodiments of the present invention, the source-side display capability management module 110 has a built-in signed "display capability file" (which includes EDID and mode policy), and provides EDID and simulated HPD timing signals through local I²C read-only mode. The source-side external network content host reads the EDID data and simulated HPD timing signals in the source-side display capability management module 110. That is, as mentioned above, when the source-side external network content host 100 reads signals through DDC, the DDC handshake is "intercepted" by the source-side display capability management module 110, and the source-side display capability management module 110 locally replies with a pre-stored (or forged) EDID.

[0032] According to some embodiments of the present invention, the "Display Capability Profile" (EDID content and mode policy) is issued and version-managed using asymmetric signatures.

[0033] According to some embodiments of the present invention, the "display capability profile" supports "read-only OTP / PUF binding" to prevent on-site tampering.

[0034] The audio / video main link transmitting unit 120 is used to connect to the audio / video output pin of the standard audio / video output port to receive the audio / video signals and send them to the unidirectional transmission link.

[0035] A one-way transmission link is used to send the audio and video signals to the decoding and retiming unit 160.

[0036] The decoding and retiming unit 160 is used to demodulate the received signal and retime it to a standard audio and video signal. The intranet receiver 170 is used to receive and play standard audio and video signals. The intranet receiver 170 only displays or collects data locally on the intranet and does not send signals to the outside.

[0037] According to some embodiments of the present invention, the standard audio / video output port includes an HDMI output port (hereinafter referred to as an HDMI port). In the prior art, the CEC pin allows users to control devices connected via HDMI using a remote control, but in this invention, the CEC pin is cut off or sealed. Because the present invention physically cuts off (or seals) the CEC pin in the HDMI port, this means that the source-side external network content host 100 will absolutely not respond to or send any CEC control commands. It cannot control other devices, nor can it be controlled by other devices, completely eliminating this "backhaul control." After completing a local handshake with the source-side display capability management module 110 and being locked by the policy firmware, the source-side external network content host 100 sends a standard TMDS signal (Minimized Transmission Differential Signaling) to the main link transmission unit 120. The decoding and retiming unit 160 demodulates and retims the optical signal to standard TMDS.

[0038] Figure 2 A schematic diagram of the signal transmission process on the source side according to some embodiments of the present invention is shown.

[0039] Please refer to the attached diagram. The source-side external network includes a source-side external network content host 100; a source-side display capability management module 110; a main link transmission unit 120; and an electro-optical conversion unidirectional optical transmitter 130.

[0040] The source-side external network content host 100 is communicatively connected to the source-side display capability management module 110. According to some embodiments of the present invention, the source-side external network content host 100 communicates with a local I / O network. 2The C-bus reads the EDID from the source-side display capability management module 110, where the EDID is read-only data. Simultaneously, the source-side display capability management module 110 also provides the source-side external network content host 100 with a locally emulated HPD timing signal (hot-plug detection timing signal) and a mode policy. The source-side display capability management module 110 may also include policy firmware. This policy firmware is used to execute a predetermined mode policy, namely, under zero backhaul conditions, fixing the resolution and refresh rate, and disabling HDR, DSC, jitter, scaling, and CEC.

[0041] On the main signal path, after completing the local handshake with the source-side external network content host 100 and being locked by the policy firmware, the source-side external network content host 100 sends standard audio and video signals (such as TMDS signals, i.e., minimized transmission differential signals) to the main link transmission unit 120. The main link transmission unit 120 receives the electrical signal input and transmits it to the electro-optical conversion unidirectional optical transmitter 130. The electro-optical conversion unidirectional optical transmitter 130 is a device with only transmission function (TX only), which is responsible for converting the electrical signal into an optical signal and transmitting it outward.

[0042] Through this architecture, the output of the source-side external network content host 100 is strictly limited by the policy firmware, and its control channel achieves localized physical isolation from downstream devices.

[0043] In addition to the HDMI transmission lines mentioned above, there are also video transmission lines such as VGA, DVI, DP, and USB-C. These transmission lines also include similar audio / video output pins, display data channel pins, hot-plug detection channel pins, and consumer electronics control pins. Therefore, the above embodiments of the present invention are also applicable to video transmission lines such as VGA, DVI, DP, and USB-C, and the standard audio / video output ports include HDMI, VGA, DVI, DP, and USB-C output ports. For simplicity, they will not be described in detail here.

[0044] This application also provides an information transmission method based on the aforementioned physical isolation information transmission system between internal and external networks. This method achieves a secure unidirectional video transmission link through hardware isolation and local simulation mechanisms. The method includes the following steps: The source-side external network content host 100 initiates an extended display identifier data read request to the source-side display capability management module 110; In response to the request, the source-side display capability management module 110 returns a pre-stored signed display capability profile and a simulated hot-plug detection timing signal to the source-side external network content host 100. The display capability profile includes extended display identification data and mode strategy. The source-side external network content host 100 outputs audio and video signals to the audio and video main link sending unit in the locked graphics card output mode according to the mode policy; The audio / video main link transmission unit 120 receives audio and video signals and transmits them to the unidirectional transmission link; The one-way transmission link sends the audio and video signals to the decoding and retiming unit 160; The decoding and re-timing unit 160 demodulates and re-tims the received signal into a standard audio and video signal; and The intranet receiver 170 receives and plays standard audio and video signals.

[0045] As mentioned above, the unidirectional transmission link includes: an electro-optical conversion unidirectional optical transmitter 130, a unidirectional optical fiber 140, and a photoelectric conversion unidirectional optical receiver 150. The unidirectional transmission link can also be any link capable of physically transmitting signals in one direction, including but not limited to unidirectional serial cables.

[0046] Further exemplary implementations are described below.

[0047] like Figure 3 As shown, at point 1, the source-side external network content host 100 initiates an EDID read request to the source-side display capability management module 110. The EDID is local read-only data.

[0048] At points 2 and 3, the source-side display capability management module 110 responds to the request by returning a signed display capability profile and a simulated HPD timing signal (local simulation) to the source-side external network content host. The source-side display capability management module 110 generates the simulated HPD timing signal using local MCU simulation to simulate the access status of the display device on the receiving side.

[0049] The order of 1, 2, and 3 above does not have to be strictly followed as described above and can be adjusted as needed.

[0050] At point 4, after receiving the simulated HPD timing signal and the signed display capability file, the source-side external network content host 100 selects and locks a fixed mode, such as 1080p60 or 4K30, according to the mode strategy (such as "mode locking").

[0051] At point 5, after the display mode is locked, the source-side external network content host 100 outputs a main link video signal, such as a TMDS signal, to the main link sending unit 120 with stable parameters.

[0052] At point 6: The main video link sending unit receives the audio and video signals and sends them to the electro-optical conversion unidirectional light transmitter. The unidirectional light transmitter receives the audio and video signals, converts them into optical signals, and performs unidirectional light transmission. At point 7, a unidirectional optical fiber transmits the optical signal unidirectionally to a photoelectric conversion unidirectional optical receiver. At point 8, a photoelectric conversion unidirectional optical receiver receives the optical signal and converts it into an electrical signal. The decoding and retiming unit demodulates and retims the electrical signal into a standard TMDS audio and video signal.

[0053] At 8 locations, the intranet receiver collects the electrical signals and converts them back into audio and video signals for display.

[0054] As shown in the highlighted area at the bottom of the attached diagram, there is no physical "backhaul" channel for control signals such as DDC, HPD, or CEC in the entire transmission link from the external network content host 100 to the internal network receiver 170. Furthermore, the receiving devices (such as the photoelectric conversion unidirectional optical receiver 150 and the decoding and retiming unit 160) do not contain any optical transmitting devices, thus completely eliminating the possibility of data backhaul at the hardware level and achieving strict unidirectional data flow and secure isolation.

[0055] According to some embodiments of the present invention, the locked graphics card output mode includes a fixed resolution and refresh rate, and disables high dynamic range, display stream compression, jitter, scaling, and consumer electronics control functions.

[0056] According to some embodiments of the present invention, the source-side external network content host communicates through a local I... 2 The C bus reads extended display identifier data from the source-side display capability management module. The extended display identifier data is read-only data.

[0057] According to some embodiments of the present invention, the consumer electronics control pin is cut off or sealed.

[0058] According to some embodiments of the present invention, the source-side external network content host reads pre-stored extended display identification data and simulated hot-plug detection timing signals from the source-side display capability management module through the display data channel pin and the hot-plug detection channel pin, respectively; and leaves the consumer electronics control pin idle.

[0059] In addition to the HDMI transmission lines mentioned above, there are also video transmission lines such as VGA, DVI, DP, and USB-C. These transmission lines also include similar audio / video output pins, display data channel pins, hot-plug detection channel pins, and consumer electronics control pins. Therefore, the above embodiments of the present invention are also applicable to video transmission lines such as VGA, DVI, DP, and USB-C, and the standard audio / video output ports include HDMI, VGA, DVI, DP, and USB-C output ports. For simplicity, they will not be described in detail here.

[0060] The following effects can be achieved through this invention: 1. Absolutely unidirectional and physically irreversible: There are no DDC / HPD / CEC / optical RX / electrical RX devices or traces connected to the receiving side on the source side; there are no light-emitting / electrical-emitting devices on the receiving side that can be used for backhaul; therefore, even if the internal network side is compromised, it is impossible to affect the configuration of the external network host and the pixel output from the physical layer.

[0061] 2. Plug and play, predictable bandwidth: Local EDID / HPD emulation at the source makes the graphics card think it is connected to a display device with fixed capabilities; dynamic negotiation such as HDR / DSC / jitter / scaling / color gamut switching is prohibited, the output mode is stable, and the link bandwidth is constant and measurable.

[0062] 3. Balancing engineering practicality and acceptability: Through "visible physical evidence" such as tamper-proof potting, removal of RX components / traces, and absence of test points (CEC pins are cut off or sealed), it facilitates third-party safety assessments / military inspections; it supports common resolutions such as 1080p / 4K, and the intranet terminal can choose direct display or data collection and storage, covering scenarios such as information release / command dashboard / security control.

[0063] 4. Resistance to "soft loops" and "side channels": Eliminates loops directly at the physical layer without relying on upper-layer protocol blocking (such as TCP / UDP / DNS); weakens the feasibility of pixel-level covert coding through pattern locking and pixel path.

[0064] It should be noted that, for ease of understanding, this application has broken down each step in the method and each module in the system in detail. However, those skilled in the art will understand that, depending on the actual implementation needs, each step and module can be further broken down or reorganized, and these are all within the scope of the present invention.

Claims

1. A physical isolation information transmission system for internal and external networks based on a unidirectional channel, characterized in that, include: Source-side external network content host, source-side display capability management module, audio and video main link sending unit, one-way transmission link, decoding and retiming unit, and internal network receiver; The source-side external network content host includes a graphics card and a standard audio / video output port. The standard audio / video output port includes audio / video output pins, display data channel pins, hot-plug detection channel pins, and consumer electronics control pins. The source-side external network content host outputs standard audio / video signals through the audio / video output pins. The source-side external network content host connects to the source-side display capability management module to read pre-stored signed display capability profiles and simulated hot-plug detection timing signals from the source-side display capability management module. The display capability profile includes extended display identification data and mode policies. The source-side external network content host also outputs audio / video signals in a locked graphics card output mode according to the mode policies. The display data channel pins, hot-plug detection channel pins, and consumer electronics control pins are left unused. The source-side display capability management module is used to return display capability profiles and simulated hot-plug detection timing signals to the source-side external network content host; The audio / video main link transmitting unit is connected to the audio / video output pin to receive audio / video signals and send them to the unidirectional transmission link; A one-way transmission link is used to send the audio and video signals to the decoding and retiming unit; The decoding and retiming unit is used to demodulate the received signal and retime it to a standard audio and video signal. The intranet receiver is used to receive and play standard audio and video signals.

2. The system according to claim 1, characterized in that, The graphics card output mode of the locked source-side external network content host includes fixed resolution and refresh rate, and disables high dynamic range, display stream compression, jitter, scaling and consumer electronics control functions.

3. The system according to claim 2, characterized in that, The standard audio and video output ports include HDMI, VGA, DVI, DP, and USB-C output ports.

4. The system according to claim 2, characterized in that, The display data channel pin and the hot-plug detection channel pin are connected to the source-side display capability management module to read pre-stored extended display identification data and simulated hot-plug detection timing signals from the source-side display capability management module, respectively. And the aforementioned consumer electronics control pins are unused.

5. The system according to claim 2, characterized in that, The consumer electronics control pins are cut off or sealed.

6. The system according to claim 2, characterized in that, The system also includes a unidirectional transmission link, which comprises: an electro-optical conversion unidirectional optical transmitter for receiving audio and video signals and converting them into optical signals; a unidirectional optical fiber for transmitting the optical signals unidirectionally to an opto-optical conversion unidirectional optical receiver; and an opto-optical conversion unidirectional optical receiver for receiving the optical signals and converting them into electrical signals before outputting them.

7. An information transmission method based on the internal and external network physically isolated information transmission system according to any one of claims 1-6, characterized in that, include: The source-side external network content host initiates an extended display identifier data read request to the source-side display capability management module; In response to the request, the source-side display capability management module returns a pre-stored signed display capability profile and a simulated hot-plug detection timing signal to the source-side external network content host. The display capability profile includes extended display identification data and mode strategy. The source-side external network content host outputs audio and video signals to the audio and video main link sending unit in the locked graphics card output mode according to the mode policy; The audio / video main link transmission unit receives audio and video signals and sends them to the unidirectional transmission link; The one-way transmission link sends the audio and video signals to the decoding and retiming unit; The decoding and retiming unit demodulates and retims the received signal into a standard audio and video signal; as well as The intranet receiver receives and plays standard audio and video signals.

8. The method according to claim 7, characterized in that, The standard audio and video output ports include HDMI, VGA, DVI, DP, and USB-C output ports.

9. The method according to claim 7, characterized in that, The source-side external network content host communicates through a local I / O network. 2 The C bus reads extended display identifier data from the source-side display capability management module. The extended display identifier data is read-only data.

10. The method according to claim 7, characterized in that, The source-side external network content host reads pre-stored extended display identifier data and simulated hot-plug detection timing signals from the source-side display capability management module through the display data channel pin and the hot-plug detection channel pin, respectively; and leaves the consumer electronics control pin idle.

Images