WO2021092778A1

WO2021092778A1 - Microphone blocking apparatus

Info

Publication number: WO2021092778A1
Application number: PCT/CN2019/117719
Authority: WO
Inventors: Hongwei Xu
Original assignee: Mount Schiehallion Ltd; Global Bridge Industry Co., Ltd
Priority date: 2019-11-12
Filing date: 2019-11-12
Publication date: 2021-05-20

Abstract

A microphone blocking apparatus comprising: a digital connector for connecting the apparatus to a digital port of an electronic device, the digital connector comprising: a power connection for connecting to a power pin of the digital port; a ground connection for connecting to a ground pin of the digital port; and a data connection for connecting to a data pin of the digital port, wherein the apparatus further comprises an attenuator adapted to attenuate a signal transmitted by the data connection.

Description

Microphone Blocking Apparatus

The present invention relates to apparatus for preventing audio recording by an electronic device. In particular, but not exclusively, the present invention relates to microphone blocking apparatus.

It is known that there are a variety of spyware programs that can turn on the internal microphone of a user’s device without the user’s knowledge or consent. The user’s conversations and/or calls can then be surreptitiously recorded and uploaded. The device may be a mobile phone, laptop or the like. The vast majority of devices do not have internal hardware protection to prevent eavesdropping.

A microphone blocker is a device that can prevent audio hacking of devices. Typically, the microphone blocker is a dummy jack that is inserted into the 3.5 mm jack socket of the device. The device may be ‘tricked’ into thinking that an external microphone is plugged in and, consequently, the signal from the internal microphone is disabled or ignored. However, successful operation of the microphone blocker depends on the internal scheme of the device, which may fully block the microphone without the possibility of recovering data, or just disregard the signal from the internal microphone.

Apple removed the traditional 3.5mm headphone jack socket from the iPhone 7 in 2016, forcing users to connect their headphones via the Lightning connector port. Lightning is an 8-pin connector which carries a digital signal. Therefore, audio data sent to headphones via this connection is fully digital and must be converted (by the headphones or an adapter) to analog before being playable. Similarly, the analog audio signal from an external microphone must be converted to digital before being received at the device.

USB-C is a recent standard for charging and powering devices and for transferring data. USB-C has the highest data transmission speed of 10Gbps, and its maximum power transmission speed can reach 100W. Increasingly, it is replacing the analog 3.5 mm jack socket of devices. In 2018, Apple announced that their new range of iPad Pros will replace Lightning with USB-C.

USB-C is also a fully digital connection. However, the specification provides an Audio Adapter Accessory Mode (AAAM) . This allows devices with a USB-C port to support analog headsets, providing four standard analog audio connections (Left, Right, Microphone, and Ground) . In this mode, all digital connections are disconnected from the connecting device, and certain pins become reassigned for analog outputs or inputs. AAAM is entered when both CC pins are shorted to GND. The D-and D+ pins become audio output left L and right R, respectively. The SBU pins become a microphone pin MIC, and the analog ground AGND, the latter being a return path for both outputs and the microphone. As analog headsets are typically passive devices, there need not be any connection made to the power pins VBUS. However, AAAM does allow concurrent charging of a connected device using VBUS and GND.

When connecting to digital ports, conventional microphone blockers are ineffective as it is harder to trick the device into thinking that an external microphone is connected. This depends on the internal scheme of the device. In some cases, the connected device must at least be drawing power. In other cases, a dummy microphone connection is insufficient and there must be some kind of activity/signal on this connection. Also, the connected device may have to be an authorised product or it will be disregarded by the device.

It is desirable to provide a microphone blocking apparatus that is suitable for use with fully digital connections such as Lightning and USB-C. It is desirable to provide a microphone blocking apparatus that operates on a different principle than conventional microphone blocking apparatus.

According to the present invention there is provided a microphone blocking apparatus comprising:

a digital connector for connecting the apparatus to a digital port of an electronic device, the digital connector comprising:

a power connection for connecting to a power pin of the digital port;

a ground connection for connecting to a ground pin of the digital port; and

a data connection for connecting to a data pin of the digital port,

wherein the apparatus further comprises an attenuator adapted to attenuate a signal transmitted by the data connection.

Optionally, the attenuator comprises an attenuation circuit.

Optionally, the attenuation circuit comprises a voltage divider circuit.

Optionally, the attenuator is adapted to attenuate the magnitude of the signal transmitted by the data connection to substantially zero.

Alternatively or in addition, the attenuation circuit comprises a filter circuit for removing a component of the data signal.

Optionally, the filter circuit comprises an RC filter for attenuating one or more frequencies of the data signal. Optionally, the filter circuit is adapted to attenuate a frequency range of 300 Hz to 3 kHz.

Optionally, the apparatus includes a digital decoder. Optionally, the digital decoder is adapted to convert a two bit digital output signal from the data pin of the digital port to an eight bit digital signal.

Optionally, the apparatus includes an audio decoder. Optionally, the audio decoder is adapted to convert a digital signal to an analog audio signal. Optionally, the audio decoder is adapted to convert the eight bit digital signal generated by the digital decoder to an analog audio signal.

Optionally, the attenuator is adapted to attenuate the signal generated by the audio decoder.

Optionally, the data pin of the digital port comprises a microphone pin for receiving a signal from an external microphone.

Optionally, the apparatus is further adapted to attenuate the signal transmitted by the power connection.

Optionally, the attenuator is adapted to attenuate the magnitude of the signal transmitted by the power connection to substantially zero.

The invention will be described below, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is an end view of a Lightning connector port;

Figure 2 is a circuit diagram of a first embodiment of a microphone blocking apparatus according to the present invention; and

Figure 3 is a circuit diagram of a second embodiment of a microphone blocking apparatus according to the present invention.

[Rectified under Rule 91, 12.02.2020]
Figure 4 shows the pinout for a Lightning connector port 100. The port 100 has eight pins 102 numbered one to eight as shown in the figure. The function of each pin is listed in the table below.

Pin	Name	Description
Pin
1	GND	Ground
Pin
2	L0p	Data Lane 0 positive
Pin
3	L0n	Data Lane 0 negative
Pin
4	ID0	Identification/control 0
Pin 5	PWR	Power (charger or battery)
Pin 6	L1n	Data Lane	1 negative
Pin
7	L1p	Data Lane	1 positive
Pin
8	ID1	Identification/control 1

Figure 2 shows a circuit diagram of a first embodiment of the present invention. The apparatus 10 comprises a digital connector 20 for connecting the apparatus 10 to the Lightning port of an electronic device.

The digital connector 20 has a power connection DW for connecting to the power pin PWR of the port 100 and a ground connection GND for connecting to a ground pin GND of the port 100. This allows power to be drawn from the device and completes the circuit.

The digital connector 20 has data connections D+ and D-for connecting to the data pins L1+ and L1-of the port 100. No connection is made to data pins L0+ and L0-of the port 100.

A connection is also made to identification pin ID1 of the port 100. If the apparatus is an Apple approved product, the correct authorisation data can be supplied to pin ID1. No connection is made to pin ID0 of the port 100.

The apparatus 10 includes a digital decoder 30, specifically a 3-to-8 line decoder. A digital decoder is a combinational logic circuit that converts binary information from the n coded inputs to a maximum of 2 ⁿ unique outputs. The digital decoder 30 is adapted to convert the signal from the data pins L0+ and L0-of the port 100 and the power signal received at VIN to an eight bit digital signal. This signal is output from the digital decoder 30 using output pins D0 to D7 as shown in Figure 2.

This allows more flexible signal processing of the data signals. It should also be noted that the power signal is being treated as one of the inputs for signal processing.

The ground pin GND of the digital decoder 30 is connected to the ground pin GND of the port 100. The digital decoder 30 includes a memory for storing the authorisation data which is supplied to pin ID1 via the connector 20.

Signals outputted from pins D0 to D7 of the digital decoder 30 are passed to a number of AND gates 40 before being passed to an audio decoder 50. The audio decoder 50 converts the signals to an analog audio signal.

The apparatus 10 also includes an attenuator for attenuating the audio signal. The attenuator comprises an attenuation circuit 60 which comprises a number of resistors and capacitors.

The attenuation circuit 60 provides a voltage divider circuit which reduces the magnitude of the signal. The attenuation circuit 60 can be configured to attenuate the magnitude of the signal to substantially zero.

The resistors and capacitors can also be configured to provide a filter circuit for removing certain frequencies of the signal. Of particular interest is the frequency range of 300 Hz to 3 kHz which is a frequency range of the human voice. The RC filter can be configured to attenuate this frequency range.

The data pins of the Lightning port are used to send audio data to connected headphones or receive audio data from a connected microphone. The microphone blocking apparatus 10 connects to these pins. It also draws power from the device and can provide the correct authorisation data. Typically, the device supplies current to either the internal microphone or an external one. If the apparatus 10 is inserted into the device, the external microphone operation takes preference over the internal microphone circuits in the device. Therefore, in the majority of cases, the device will believe that an external microphone is connected and will disable or disregard the internal microphone.

If the spyware is able to override this and activate the internal microphone, the signal will be output to the apparatus 10 when connected. The apparatus 10 will process this signal, converting it to an analog signal which is then attenuated to substantially zero. Any remaining signal will also be highly attenuated in the frequency range of 300 Hz to 3 kHz which corresponds to the range for human voice.

Figure 3 shows the pinout for a USB-C connector port 100. The port 100 has twenty four pins 102 comprising two sets of twelve pins so that the USB-C connector is reversible. The function of each pin is listed in the table below.

Figure 4 shows a circuit diagram of a second embodiment of the present invention. Like features are given like reference numerals. In this embodiment, the apparatus 10 comprises a digital connector 20 for connecting the apparatus 10 to a USB-C port of an electronic device.

The apparatus 10 is configured to initiate Audio Adapter Accessory Mode (AAAM) . No connection is made to the digital connections (TX1+, TX1-, RX1+, RX1-, TX2+, TX2-, RX2+ and RX2-) . Both CC pins are shorted to GND.

In this mode, the D-and D+ pins become audio output left L and right R, respectively. Also, the SBU pins become a microphone pin MIC and the analog ground AGND. As this is a passive mode, no connection is made to the power pins VBUS. This will not cause the device to disregard the apparatus 10 since this is normal when connecting passive devices in the AAAM.

In this embodiment, since the device is sending/receiving an analog signal via the USB-C connector, there is no digital or audio decoding of the signals. The D-and D+ pins (audio output left L and right R) and the SBU pins (microphone pin MIC and analog ground AGND) are all directly connected to the attenuation circuit 60. Any signal is attenuated to substantially zero.

In this embodiment, there is a dedicated microphone pin MIC and this is connected to the apparatus. Therefore, it is highly likely that the device will believe that an external microphone is connected and will disable or disregard the internal microphone. Even if the spyware is able to override this and activate the internal microphone, the signal will be attenuated to substantially zero.

The present invention provides a microphone blocking apparatus that is suitable for use with fully digital connections such as Lightning and USB-C. The apparatus has the same capability as conventional apparatus to trick the device into believing that an external microphone is connected. And it is capable of doing this even for a fully digital connection. However, it also offers an additional safeguard by attenuating any signal which may be being recorded.

Various modifications and improvements can be made to the above without departing from the scope of the invention.

Claims

A microphone blocking apparatus comprising:

a digital connector for connecting the apparatus to a digital port of an electronic device, the digital connector comprising:

a power connection for connecting to a power pin of the digital port;

a ground connection for connecting to a ground pin of the digital port; and

a data connection for connecting to a data pin of the digital port,

wherein the apparatus further comprises an attenuator adapted to attenuate a signal transmitted by the data connection.
An apparatus as claimed in Claim 1, wherein the attenuator comprises an attenuation circuit.
An apparatus as claimed in Claim 2, wherein the attenuation circuit comprises a voltage divider circuit.
An apparatus as claimed in Claim 1, wherein the attenuator is adapted to attenuate the magnitude of the signal transmitted by the data connection to substantially zero.
An apparatus as claimed in Claim 1, wherein the attenuator comprises a filter circuit for removing a component of the data signal.
An apparatus as claimed in Claim 5, wherein the filter circuit comprises an RC filter for attenuating one or more frequencies of the data signal.
An apparatus as claimed in Claim 6, wherein the filter circuit is adapted to attenuate a frequency range of 300 Hz to 3 kHz.
An apparatus as claimed in Claim 1, wherein the apparatus includes a digital decoder.
An apparatus as claimed in Claim 8, wherein the digital decoder is adapted to convert a two bit digital output signal from the data pin of the digital port to an eight bit digital signal.
An apparatus as claimed in Claim 1, wherein the apparatus includes an audio decoder adapted to convert a digital signal to an analog audio signal.
An apparatus as claimed in Claim 10, wherein the audio decoder is adapted to convert the eight bit digital signal generated by the digital decoder to an analog audio signal.
An apparatus as claimed in Claim 10, wherein the attenuator is adapted to attenuate the signal generated by the audio decoder.
An apparatus as claimed in Claim 1, wherein the data pin of the digital port comprises a microphone pin for receiving a signal from an external microphone.
An apparatus as claimed in Claim 1, wherein the apparatus is further adapted to attenuate the signal transmitted by the power connection.
An apparatus as claimed in Claim 14, wherein the attenuator is adapted to attenuate the magnitude of the signal transmitted by the power connection to substantially zero.