SRTP Mechanism in Asterisk

Asterisk Asterisk SIP
1

Hello, I want to ask about the mechanism that occurs on the asterisk server when VoIP communication activates the SRTP protocol as a payload security media.

In peer2peer communication that I have tried with activated SRTP, using Wireshark I found that the packet payload received by the asterisk server from endpoint 1 has a difference with the packet payload sent by the asterik server to endpoint 2.

Then, if the communication is broadcast, then how can the asterisk server process data that has been encrypted by the SRTP so the data from endpoint 1 not sent to himself?

2

Media is encrypted as it exits Asterisk and is decrypted as it enters Asterisk. Internally the media is in the clear, we don’t act as a proxy so each leg is indepedent.

3

So the asterisk itself already has a mechanism to do the encryption and decryption process using the AES ICM method which is the default encryption method on SRTP ?

4

Yes, it uses the libsrtp library.

5

Thanks for your answers.

6

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