[asterisk-users] Sending SRTP to Asterisk Gateway ends up in authentication failure

[Karsten Asche]

Hi @ all,

I´m trying to send SRTP packets to an asterisk 1.8.4 Gateway with my own developed softphone.
I am using libsrtp to prtect the rtp packets.
At the moment I do SRTP without a key management and creating my key with the crypto_get_random function
of libsrtp. The key size is 30B. For creating the SDP offer with crypto I encode the key to base64.

The encryption type I want to use is AES_CM_128_HMAC_SHA1_80.

for crypto_policy I use the crypto_policy_set_rtp_default.
By sending the protected SRTP packets Asterisk Gateway ends up with SRTP_unprotect: authentication failure.

My payload is 240B large and after protecting 250B.

What could be wrong? How I can find out if I´m using same key and key derivations like asterisk?

Best Regards

Karsten