Cisco Systems WRP400 Manual De Usuario

Secure Call Implementation

ATA Administration Guide

72

This section describes secure call implementation with the ATA device . It includes 
the following topics:

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•

•

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This is an advanced topic meant for experience installers. See also the

 LVS 

Provisioning Guide

. 

A secure call is established in two stages. The first stage is no different from 
normal call setup. The second stage starts after the call is established in the 
normal way with both sides ready to stream RTP packets. 

In the second stage, the two parties exchange information to determine if the 
current call can switch over to the secure mode. The information is transported by 
base64 encoding embedded in the message body of SIP INFO requests, and 
responses using a proprietary format. If the second stage is successful, the ATA 
device plays a special Secure Call Indication Tone for a short time to indicate to 
both parties that the call is secured and that RTP traffic in both directions is being 
encrypted. 

If the user has a phone that supports call waiting caller ID (CIDCW) and that 
service is enabled, the CID will be updated with the information extracted from the 
Mini-Certificate received from the remote party. The Name field of the CID will be 
prepended with a ‘$’ symbol. Both parties can verify the name and number to 
ensure the identity of the remote party.