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AFAIK, there are two ways in which the tones can be sent. 1. In the regular audio stream (AKA in-band) so anyone who can listen to the phone call, can also lis
by Sreyanth 8y ago
AFAIK, there are two ways in which the tones can be sent.
1. In the regular audio stream (AKA in-band) so anyone who can listen to the phone call, can also listen to these tones. These tones can be mapped to the digits pressed.
2. In a separate RTP payload (AKA out-of-band) so not everyone can read / listen to this stream of signals / tones. RFC 4733 (earlier it was RFC 2833) specifies the format of this RTP payload. This is what the payment via phone systems might be using.
There is a secure RTP with encryption support, but I am not sure if it can be implemented end-to-end to avoid anyone in middle (not a man-in-middle attacker, but a genuine carrier / network) to see these DTMFs. Just unable to imagine how this works :)