4 ms·

according to security principles, "can" = we must assume that it will or has been, given the proper motivation. the iphone has a low-power asic whose sole purp

according to security principles, "can" = we must assume that it will or has been, given the proper motivation. the iphone has a low-power asic whose sole purpose is to listen for "hey siri" with relaxed confidence intervals. the real voice processing isn't done until the main cpu is woken by this asic. because of this, we can identify discrete modes of operation in the iphone, one of which is incapable of doing arbitrary "spying". based on the article, it sounds like the alexa doesn't have this affordance. while unsurprising in this case, i don't think we must accept that anything with an internet-connected microphone has the capability to always listen to what you say.

paxy 9y ago
Alexa and all other "always-listening" devices do have the standard on-chip processing mechanism. The article is about how the trigger can be expanded from a single word to a broader range of sounds.
deleted 9y ago
[deleted]
DSMan195276 9y ago
I'm not sure the distinction is as notable as you're making it. The iPhone as you describe it is perfectly capable of listening to everything you say, it just has to never release control of the mic to the low-power ASIC. I'm also not sure the article actually indicates what you're saying, it's kind-of vague. For example, it never states that anybody was able to actually program Alexa with a new wake-word, just the possibility of being able to create different signatures that could be used as wake-words. And the description of how they prevent things like the superbowl ad could all be done after Alexa detects the wake-word wakes up the main processor, but before Alexa actually responds to the user. I don't see anything in the article that indicates Alexa can't be using a separate chip dedicated to listening to the wake-word. To that end, not to long ago a Reddit user claimed that Alexa did have two separate modes it operated in [0]. Which, it is entirely possible they could be lying, but you could always just open the thing up and take a look. But even if it does have a separate chip my previous point about the iPhone still applies, so besides power-usage I don't think it is extremely notable. [0] https://np.reddit.com/r/Showerthoughts/comments/7m91u9/if_google_devices_only_start_listening_once_you/drsdxe1/?sh=c90d0649&st=JBO70BSD https://np.reddit.com/r/Showerthoughts/comments/7m91u9/if_go...
- secabeen 9y ago
  The other angle is that were Alexa actually recording and sending voice data frequently, it would show up in the traffic data. Unless they're smuggling past recordings along piecemeal along with actual recordings, traffic analysis would work.
  - Klathmon 9y ago
    Unless they are capable of doing the speech-to-text on-device, then the amount of data is negligible. Hell, if they were really crafty they could have it listen for a specific phrase or word, then send back as little as a single byte signifying that it was heard. (I own an echo and a few Google homes, and I don't actually think this is happening, but the idea is kind of fun to chase)
    - sitkack 9y ago
      > Unless they are capable of doing the speech-to-text on-device, then the amount of data is negligible. What is the lowest bitrate codec and how does it compare to the plaintext version?
      - Klathmon 9y ago
        Well considering text is literally hundreds of bytes, I can't imagine audio would be able to keep up.
        sitkack 9y ago
        Take a look at the BoE calc that someone else did in this thread, it might shed some light on what is possible.
      - deleted 9y ago
        [deleted]
    - secabeen 9y ago
      Yeah, that is an interesting idea. I'm not sure anyone is making an ASIC for speech-to-text right now, but if they were, it could enable this sort of thing. Might show up in a teardown, though. A General Purpise CPU could of course, do it, but that would push the bill of materials for the device up quite a bit.
erichurkman 9y ago
iPhone vs. Alexa, HomePod, Google Home: phones are often on battery power. They need a low-power mode for listening otherwise it will kill user batteries. A device plugged into an outlet? No incentive for power saving.
- paxy 9y ago
  Even Amazon, with all the server capacity in the world, is not going to be able to store and process every sound heard by every Alexa in real time.
  - throwaway2048 9y ago
    no, but its entirely feasable to store all spoken word transcripts.
  - pdkl95 9y ago
    > is not going to be able to store Voice codecs like AMR[1] (or GSM-HR) only need 2-3MB/hr. A trivial noise gate[2] that cuts out silence should allow a recording duty cycle under ~1%. Amazon can easily store all the voice recording they want. > and process ... in real time Processing isn't that expensive once you have a trained classifier. However, realtime processing often isn't necessary. [1] https://en.wikipedia.org/wiki/Adaptive_Multi-Rate_audio_codec https://en.wikipedia.org/wiki/Adaptive_Multi-Rate_audio_code... [2] https://en.wikipedia.org/wiki/Noise_gate https://en.wikipedia.org/wiki/Noise_gate
    - rootw0rm 9y ago
      Excellent response.
    - zeta0134 9y ago
      I don't doubt that what you say is correct, but I think the author's point is that even with those optimizations, the sheer amount of data from [Every Alexa in the world] * [Every second of every day] is too much for any remote service to process. The wake word needs to be handled locally so that the remote service is only involved when needed. The amount of data for a single recording can be quite small, but multiplied by a large population it still adds up in a hurry.
squeaky-clean 9y ago
since Siri is mostly processed remotely ("in the cloud") you can test this by trying Hey Siri in airplane mode. It will hear it's name but can't act any further.

paxy 9y ago

Alexa and all other "always-listening" devices do have the standard on-chip processing mechanism. The article is about how the trigger can be expanded from a single word to a broader range of sounds.

deleted 9y ago

[deleted]

DSMan195276 9y ago

I'm not sure the distinction is as notable as you're making it. The iPhone as you describe it is perfectly capable of listening to everything you say, it just has to never release control of the mic to the low-power ASIC. I'm also not sure the article actually indicates what you're saying, it's kind-of vague. For example, it never states that anybody was able to actually program Alexa with a new wake-word, just the possibility of being able to create different signatures that could be used as wake-words. And the description of how they prevent things like the superbowl ad could all be done after Alexa detects the wake-word wakes up the main processor, but before Alexa actually responds to the user. I don't see anything in the article that indicates Alexa can't be using a separate chip dedicated to listening to the wake-word. To that end, not to long ago a Reddit user claimed that Alexa did have two separate modes it operated in [0]. Which, it is entirely possible they could be lying, but you could always just open the thing up and take a look. But even if it does have a separate chip my previous point about the iPhone still applies, so besides power-usage I don't think it is extremely notable. [0] https://np.reddit.com/r/Showerthoughts/comments/7m91u9/if_google_devices_only_start_listening_once_you/drsdxe1/?sh=c90d0649&st=JBO70BSD https://np.reddit.com/r/Showerthoughts/comments/7m91u9/if_go...

secabeen 9y ago
The other angle is that were Alexa actually recording and sending voice data frequently, it would show up in the traffic data. Unless they're smuggling past recordings along piecemeal along with actual recordings, traffic analysis would work.
- Klathmon 9y ago
  Unless they are capable of doing the speech-to-text on-device, then the amount of data is negligible. Hell, if they were really crafty they could have it listen for a specific phrase or word, then send back as little as a single byte signifying that it was heard. (I own an echo and a few Google homes, and I don't actually think this is happening, but the idea is kind of fun to chase)
  - sitkack 9y ago
    > Unless they are capable of doing the speech-to-text on-device, then the amount of data is negligible. What is the lowest bitrate codec and how does it compare to the plaintext version?
    - Klathmon 9y ago
      Well considering text is literally hundreds of bytes, I can't imagine audio would be able to keep up.
      - sitkack 9y ago
        Take a look at the BoE calc that someone else did in this thread, it might shed some light on what is possible.
    - deleted 9y ago
      [deleted]
  - secabeen 9y ago
    Yeah, that is an interesting idea. I'm not sure anyone is making an ASIC for speech-to-text right now, but if they were, it could enable this sort of thing. Might show up in a teardown, though. A General Purpise CPU could of course, do it, but that would push the bill of materials for the device up quite a bit.

erichurkman 9y ago

iPhone vs. Alexa, HomePod, Google Home: phones are often on battery power. They need a low-power mode for listening otherwise it will kill user batteries. A device plugged into an outlet? No incentive for power saving.

paxy 9y ago
Even Amazon, with all the server capacity in the world, is not going to be able to store and process every sound heard by every Alexa in real time.
- throwaway2048 9y ago
  no, but its entirely feasable to store all spoken word transcripts.
- pdkl95 9y ago
  > is not going to be able to store Voice codecs like AMR[1] (or GSM-HR) only need 2-3MB/hr. A trivial noise gate[2] that cuts out silence should allow a recording duty cycle under ~1%. Amazon can easily store all the voice recording they want. > and process ... in real time Processing isn't that expensive once you have a trained classifier. However, realtime processing often isn't necessary. [1] https://en.wikipedia.org/wiki/Adaptive_Multi-Rate_audio_codec https://en.wikipedia.org/wiki/Adaptive_Multi-Rate_audio_code... [2] https://en.wikipedia.org/wiki/Noise_gate https://en.wikipedia.org/wiki/Noise_gate
  - rootw0rm 9y ago
    Excellent response.
  - zeta0134 9y ago
    I don't doubt that what you say is correct, but I think the author's point is that even with those optimizations, the sheer amount of data from [Every Alexa in the world] * [Every second of every day] is too much for any remote service to process. The wake word needs to be handled locally so that the remote service is only involved when needed. The amount of data for a single recording can be quite small, but multiplied by a large population it still adds up in a hurry.

squeaky-clean 9y ago

since Siri is mostly processed remotely ("in the cloud") you can test this by trying Hey Siri in airplane mode. It will hear it's name but can't act any further.