asterisk users - May 2011 - Sending SRTP to Asterisk Gateway ends up in authentication failure

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?