Verify H.323 Media Encryption

To provide extra security for encrypted H.323 calls, the RealPresence Group Series system provides an encryption check code. Both parties in a call can use this check code to verify that their call is not being intercepted by a 3rd party.

The check code is a 16-digit hexadecimal number that is calculated so that the number is the same at both sites in the call. The numbers are identical if, and only if, the key generation algorithm is performed between the two sites in the call and is not intercepted and modified by a 3rd party.


  1. Establish an encrypted H.323 call between two sites.
  2. At each site, locate the Call Statistics information on the Place a Call screen of the system web interface.

    The check code also displays under Diagnostics > System > Call Statistics in the Transmit column of the Call Encryption section.

  3. Verbally verify that the code is the same at both sites.
  4. Do one of the following:
    • If the codes match, the call is secure. Proceed with the call.
    • If the codes do not match, then there is a possibility that the key exchange is compromised. Hang up the call. Next, check the network path from the local system to the far-end system to determine if the systems are experiencing a Man in the Middle attack. This occurs when a foreign device tricks the local system into creating an encryption key using information from the imposter. Then, the imposter can decode the data sent by the local system and eavesdrop on the call.