Secure Call Implementation; Enabling Secure Calls - Cisco Small Business SPA2102 Administration Manual

Configuring Voice Services

Secure Call Implementation

Secure Call Implementation
NOTE
Cisco Small Business ATA Administration Guide
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
This is an advanced topic meant for experience installers. See also the
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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