4 ms·

Yeah, I get it, but think of the things you can do with that digital signature. Joe and Bob - were they together on Sunday at 2pm? Well let's check the digita

by drblast 11y ago

Yeah, I get it, but think of the things you can do with that digital signature. Joe and Bob - were they together on Sunday at 2pm? Well let's check the digital audio signatures to see if they match. Or, John just uploaded a signature that matches our samples of "Kill the president." And a few thousand other examples.

Kenji 11y ago
That is a fair point. Especially considering that the recording can be started from the outside by a 3rd party.
nathancahill 11y ago
Not feasible. Digital signatures are a one way operation, like hashes: Let's say the audio signature of "Kill the president" is 9a0c0a6868a2a784059d9a634e4a58c0. "kill the president" in a different tone would be entirely different: ed3e3cd6be6eeb2de9b480e2c9590cc9
- stephengillie 11y ago
  So you're saying they'll have to have a database of these hashes to match against?
- _kst_ 11y ago
  The server has to compare the signature of the sound recorded by your computer to the signature of the sound recorded by your phone. The sounds will not be identical, so the signature comparison has to be able to detect whether two sound recordings are sufficiently similar. It can't use, for example, SHA1 hashes for this purpose.
  - bcg1 11y ago
    Couldn't they ignore noise below a certain threshold and create the signature just based off of the "peaks" and "troughs" so they could expect an exact match, and/or hash several samples from the recording in case some portions don't produce an exact match? Seems like there should be a way to this without revealing information about the recorded sound
- bendykstra 11y ago
  If a slightly different sound resulted in an entirely different signature, the system would be useless for comparing recordings of ambient noise, which will never be identical. You've taken the analogy with hashing too far.
- wonkaWonka 11y ago
  Eh, these are bound to be more like Shazam guess-that-tune signatures, with behavior wildly more loose than any cryptographic hash like an MD5. Conside that the web browser's desktop/laptop microphone and the cellphone/telephone microphone will probably never produce identical audio samples, if not due to the actual transducers, then simply due to proximity to various ambient audio sources like the user's breathing versus fan motors attached to a laptop shell or desktop case.
jerf 11y ago
It depends on the signature. On the "probably too simple, but..." side, record 8 seconds of audio. Normalize it. Bucket the net volume audio levels across quarter-second intervals. Fuzzy match a bit. If the levels have some change in them, and the changes match, you're in. Virtually no useful information in that signature. By contrast, if you get "clever", and want to go with that basic approach, but you want more bits to fuzzy match, so you break apart the frequency bands into 64 bands and sample on 50 millisecond intervals, and you're getting perilously close to revealing speech in the signature with enough processing. (You lose a lot, but you end up with more to work with than we privacy sensitive folks would like.) The point isn't that either of these are what they are doing. I don't expect either of those would "work" on their own; I kept them simple to describe and simple to understand for the purposes of this post. The point is the info leak on the signature can vary quite widely depending on how they do it, and without knowing the algorithm you can't speculate very effectively. It could be anything from "fairly safe" to "you might as well just send up the audio".
kazinator 11y ago
The solution to these problems is simple. 1. "Joe and Bob - were they together on Sunday at 2pm?" Joe and Bob avoid this by not authenticating using the same mechanism in the same room at the same time. 2. "John just uploaded a signature that matches our samples of 'Kill the president'". Solution 1: John understands how the authentication works by recording ambient sound, and refrains from saying things like "kill the president" during that procedure. Solution 2: John starts an Internet meme which encourages every user of this authentication mechanism to say "Kill the president" over and over again during the procedure. Now, millions of signatures match.
- task_queue 11y ago
  Most people do not consider the consequences of technology nor how to route their behavior around them.
  - kazinator 11y ago
    People can be told that the authentication method listens to their ambient sounds through their phone and PC at the same time to determine that those two pieces of equipment are in the same location, and that although their privacy is safe-guarded, they shouldn't say anything confidential during this time.
Navarr 11y ago
because you're shouting "kill the president" when you're logging into a website?

by drblast 11y ago

Kenji 11y ago

That is a fair point. Especially considering that the recording can be started from the outside by a 3rd party.

nathancahill 11y ago

Not feasible. Digital signatures are a one way operation, like hashes: Let's say the audio signature of "Kill the president" is 9a0c0a6868a2a784059d9a634e4a58c0. "kill the president" in a different tone would be entirely different: ed3e3cd6be6eeb2de9b480e2c9590cc9

stephengillie 11y ago
So you're saying they'll have to have a database of these hashes to match against?
_kst_ 11y ago
The server has to compare the signature of the sound recorded by your computer to the signature of the sound recorded by your phone. The sounds will not be identical, so the signature comparison has to be able to detect whether two sound recordings are sufficiently similar. It can't use, for example, SHA1 hashes for this purpose.
- bcg1 11y ago
  Couldn't they ignore noise below a certain threshold and create the signature just based off of the "peaks" and "troughs" so they could expect an exact match, and/or hash several samples from the recording in case some portions don't produce an exact match? Seems like there should be a way to this without revealing information about the recorded sound
bendykstra 11y ago
If a slightly different sound resulted in an entirely different signature, the system would be useless for comparing recordings of ambient noise, which will never be identical. You've taken the analogy with hashing too far.
wonkaWonka 11y ago
Eh, these are bound to be more like Shazam guess-that-tune signatures, with behavior wildly more loose than any cryptographic hash like an MD5. Conside that the web browser's desktop/laptop microphone and the cellphone/telephone microphone will probably never produce identical audio samples, if not due to the actual transducers, then simply due to proximity to various ambient audio sources like the user's breathing versus fan motors attached to a laptop shell or desktop case.

jerf 11y ago

It depends on the signature. On the "probably too simple, but..." side, record 8 seconds of audio. Normalize it. Bucket the net volume audio levels across quarter-second intervals. Fuzzy match a bit. If the levels have some change in them, and the changes match, you're in. Virtually no useful information in that signature. By contrast, if you get "clever", and want to go with that basic approach, but you want more bits to fuzzy match, so you break apart the frequency bands into 64 bands and sample on 50 millisecond intervals, and you're getting perilously close to revealing speech in the signature with enough processing. (You lose a lot, but you end up with more to work with than we privacy sensitive folks would like.) The point isn't that either of these are what they are doing. I don't expect either of those would "work" on their own; I kept them simple to describe and simple to understand for the purposes of this post. The point is the info leak on the signature can vary quite widely depending on how they do it, and without knowing the algorithm you can't speculate very effectively. It could be anything from "fairly safe" to "you might as well just send up the audio".

kazinator 11y ago

The solution to these problems is simple. 1. "Joe and Bob - were they together on Sunday at 2pm?" Joe and Bob avoid this by not authenticating using the same mechanism in the same room at the same time. 2. "John just uploaded a signature that matches our samples of 'Kill the president'". Solution 1: John understands how the authentication works by recording ambient sound, and refrains from saying things like "kill the president" during that procedure. Solution 2: John starts an Internet meme which encourages every user of this authentication mechanism to say "Kill the president" over and over again during the procedure. Now, millions of signatures match.

task_queue 11y ago
Most people do not consider the consequences of technology nor how to route their behavior around them.
- kazinator 11y ago
  People can be told that the authentication method listens to their ambient sounds through their phone and PC at the same time to determine that those two pieces of equipment are in the same location, and that although their privacy is safe-guarded, they shouldn't say anything confidential during this time.

Navarr 11y ago

because you're shouting "kill the president" when you're logging into a website?