Configure your Asterisk PBX server through Digest authentication. This scenario is used when one would like to use digest authentication with Asterisk.
You will have to use regular SIP account like User=878xxxxxxx and password=xxxxxxxx.

In this scenarios Asterisk configuration should be a bit more complex.

[general]

register => 878xxxxx:passwordxxxx@sip_proxy/my_incoming_extension

useragent => PBX
[sip_proxy]
type=friend
authuser=878xxxxxxx
username=878xxxxxxx
fromuser=878xxxxxxx
secret=passwordxxxx
host=87.238.224.117
qualify=yes
insecure=very
canreinvite=yes

Note, that it is important to set useragent parameter in [general] section as shown above, because otherwise our system will try to apply ip authentication instead
of digest. ‘register’ parameter in [general] section configures what to do with the incoming calls, in the example above such calls will be sent to context my_incoming_extension.