United States Stove Company SP8000 Technical Information download pdf (Page 71)

Configuring Voice Services

Secure Call Implementation

Cisco Small Business ATA Administration Guide 71

Secure Call Implementation

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

the following topics:

• “Enabling Secure Calls” section on page 71

• “Secure Call Details” section on page 72

• “Using a Mini-Certificate” section on page 73

• “Generating a Mini Certificate” section on page 73

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

LV S

Provisioning Guide

Enabling Secure Calls

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.

The signing agent is implicit and must be the same for all ATAs that communicate

securely with each other. The public key of the signing agent is pre-configured into

the ATA device by the administrator and is used by the ATA device to verify the

Mini-Certificate of its peer. The Mini-Certificate is valid if it has not expired, and it

has a valid signature.

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United States Stove Company SP8000 Technical Information Page 71