> Voice codecs, for example, will inadvertently reveal when the stream goes silent because they more or less stop transferring data.
Secure audio transports don't do this for what it's worth. They use Constant Bit Rate encodings. A constant number of bits are consumed every period regardless of whether there's silence. For example if you make a voice call with Signal it uses Opus CBR, an adversary suitably placed on your network path can see how long your call was, but they cannot measure silence.
With a Variable Bit Rate encoding it is possible for an adversary to not only detect silence but also estimate whether you said certain key things. For example if there's a "Project Amadeus" and you've got all the encrypted voice calls between dozens of people using a VBR codec you could write software which sifts those calls to find those which seem likely to mention "Project Amadeus" based on the data rates.
Secure audio transports don't do this for what it's worth. They use Constant Bit Rate encodings. A constant number of bits are consumed every period regardless of whether there's silence. For example if you make a voice call with Signal it uses Opus CBR, an adversary suitably placed on your network path can see how long your call was, but they cannot measure silence.
With a Variable Bit Rate encoding it is possible for an adversary to not only detect silence but also estimate whether you said certain key things. For example if there's a "Project Amadeus" and you've got all the encrypted voice calls between dozens of people using a VBR codec you could write software which sifts those calls to find those which seem likely to mention "Project Amadeus" based on the data rates.