What are various mechanisms for establishing secure channels [closed]

By Wikipedia definition of secure channel is one that protects from overhearing and tampering.

I know we can use certificates to establish a secure channel via TLS/SSL. This is possible if there is access to a CA.

If I don’t have access to a CA what other mechanisms are possible for establishing a secure channel?


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Handling metallic roughness maps colour channels

I’m trying to use a metalness/roughness workflow and I’m not sure how to translate the colour channels into the different metalness and roughness attributes. I’m not sure if there’s a standard on how to encode that information and I can’t find any online resources on how to treat the colour channels so I’m guessing that there is no standard.

I have had materials which have used only the R and B channels and having the B channel set as 0 and I have had materials that somehow use all the RGB channels and I’m confused as to why they would need a third channel to determine metallness and roughness.

My question is, how should I determine the format that the map is in and which channel corresponds to which attribute?

Update: I’ve already come to terms that I’ll probably have to compile new shaders for different materials but I’m trying to figure out a way of identifying the format that a map is in. It would appear that for one of the models I’m using, it stores its bump map in the R channel. I didn’t even know that was an option

Update 2: I imagine I’ll have to just delegate this to the asset pipeline and have the user select which channels to sample from. That or have a hardcoded format and make sure that any PBR materials imported follow that format

speaker-test returns all 6 channels to front speakers

OS: KUBUNTU 19.04 Soundcard: Creative Soundblaster ZxR Sound Setup: front (left/right), center, bass, rear (left/right)

My problem is, that all speaker outputs are played at the front speakers.

I did the following:

  • Set speaker setup at Plasma sound settings to “Analog Surround 5.1-Output + Analog Stereo-Input”
  • If I click on any rear speaker there, to test audio output, they are played on front speakers. The setup seems very faulty:
    • rear right: output on front left and right at the same time
    • rear left: output on front left and right at the same time
    • center: output on front left and right at the same time
    • front left: output on front left (one of two correct speakers)
    • front right: output on front right (one of two correct speakers)
  • I then executed alsamixer and noticed that my NVIDIA Graphics card was initially selected. I switched with F6 to my ZxR and set it up like this: enter image description here
  • I ran speaker-test -Dplug:surround51 -c6 -twav. An error message appeared and I was unable to perform the command: Error when opening the device: -2
  • I googled how to set the default device and so I did cat /proc/asound/cards:
 0 [NVidia         ]: HDA-Intel - HDA NVidia                       HDA NVidia at 0xdf080000 irq 17  1 [Creative       ]: HDA-Intel - HDA Creative                       HDA Creative at 0xdf204000 irq 19 

with kate ~/.asoundrc I set my default device:

defaults.pcm.card 1 defaults.ctl.card 1 defaults.timer.card 1 
  • after a restart speaker-test -Dplug:surround51 -c6 -twav was working: Unfortunately rear left output is on front left, rear right output is on front right, center appears to be on both front (left/right) speakers

Does anyone have any idea how I can fix this?

How could I block or at least detect the use of ultrasonic side channels or Google Nearby Messages API on my smartphone?

My question is about the use of ultrasonic messages that are part of the modern advertising ecosystem and are also used by the Google Nearby Messages API.

When it comes to advertising, the type of ultrasonic messages that I am referring to are described in this Wired article titled “How to Block the Ultrasonic Signals You Didn’t Know Were Tracking You”, from 2016. The article says (emphasis added):

The technology, called ultrasonic cross-device tracking, embeds high-frequency tones that are inaudible to humans in advertisements, web pages, and even physical locations like retail stores. These ultrasound “beacons” emit their audio sequences with speakers, and almost any device microphone—like those accessed by an app on a smartphone or tablet—can detect the signal and start to put together a picture of what ads you’ve seen, what sites you’ve perused, and even where you’ve been.

The Wired article also mentions that:

Now that you’re sufficiently concerned, the good news is that at the Black Hat Europe security conference on Thursday, a group based at University of California, Santa Barbara will present an Android patch and a Chrome extension that give consumers more control over the transmission and receipt of ultrasonic pitches on their devices.

Being that the article was from 2016, I looked at the Black Hat Europe conference from that year for more information about the Android patch. The presentation mentioned in the Wired article seems to be this one.

The presentation slides (available here) led me to the ubeacsec.org website where the researchers do have an android patch as mentioned in the Wired article. Alas that patch is a research prototype made for android-5.0.0_r3.

There is also this research paper from 2017, titled “Privacy Threats through Ultrasonic Side Channels on Mobile Devices”. The authors of this paper found out for example that

  • Advertising platforms such as Google’s Universal Analytics and Facebook’s Conversion Pixel provided services utilizing this technology. The researchers analyzed three commercial solutions: Shopkick, Lisnr and Silverpush.
  • 234 Android applications analyzed by the researchers were constantly listening for ultrasonic beacons.
  • Out of 35 stores visited in European cities, 4 were using ultrasonic beacons at the time of the research.

Anyway my interest is not just about blocking advertising trackers. Even though the marketing departments may be the largest consumer of this technology, it can be utilized in many other ways as well.

And this issue is related to another technology, namely the Google Nearby Messages API. The overview document written by Google about this technology (here) says that (emphasis added):

The Nearby Messages API is a publish-subscribe API that lets you pass small binary payloads between internet-connected Android and iOS devices. The devices don’t have to be on the same network, but they do have to be connected to the Internet.

Nearby uses a combination of Bluetooth, Bluetooth Low Energy, Wi-Fi and near-ultrasonic audio to communicate a unique-in-time pairing code between devices.

The concerns about the Nearby Messages API are:

  1. Its ability to pass small binary payloads, i.e. presumably executable code.
  2. That while it is easy to disable Bluetooth and WiFi on a smart phone, it is not so easy to disable the microphone.


Are there ways to block or at least detect the use of ultrasonic side channels or Google Nearby Messages API on my smartphone?