Summary

This Recommendation describes three methods of encryption key management, namely:

–           ISO 8732;

–           Diffie-Hellman; and

–           RSA.

They are applicable to the encryption of audiovisual signals transmitted digitally using the H.221 frame structure. The management messages defined here are transmitted within the H.221 Encryption Control Signal (ECS) channel, whose structure and use are defined in ITU-T Rec. H.233.

This revision of the Recommendation improves the overall readability of the text, removes ambiguities of certain aspects related to the exchange of asymmetric length of keys, and removes references to MLP encryption according to T.120-series Recommendations, since this effort is for further study. References to ASN.1 were also updated to the newest version of its specification.