ISMA Encryption & Authentication (ISMACryp)
An Internet Streaming Media Alliance (ISMA) specification covering "content encryption, message authentication (integrity) services, an RTP payload format and a file format for pre-encrypted content for ISMA 1.0, ISMA 2.0 and more generally any media that can be stored as elementary stream in an ISO media file [14496-12." The official name of the specification is "ISMA Encryption and Authentication" but it is unofficially (commonly) called "ISMACryp", a term used throughout the specification.
ISMACryp protocol for Wireshark relates only to the content encryption part in terms of header analysis (no decryption of encrypted payloads).
Nov. 2007 - ISMACryp 2.0 published, providing codec agnostic encryption.
Oct. 2006 - ISMACryp 1.1 released, providing support for the encryption of H.264/AVC video and HE-AAC audio for RTP transport and storage in MPEG-4 files.
XXX - Add example decoded traffic for this protocol here (as plain text or Wireshark screenshot).
The ISMACryp dissector is fully functional for analysis of ISMACryp 2.0 & 1.1 RTP streams. However, no decryption is done, only interpretation of ISMACryp headers / parameters. Currently ISMACryp configuration parameters are set via preferences as support for SDP (typically provided via SAP) is not provided.
TODO - enable automatic setup of ISMACryp parameters via SDP,if present. Currently values are set manually via preferences.
There are some ISMACryp_Preferences.
Example capture file
A complete list of ISMACryp display filter fields can be found in the display filter reference
Show only the ISMACryp based traffic:
Show only the ISMACryp traffic over UDP port XXX:
ismacryp && udp.port==XXX
Show only the ISMACryp traffic for RTP dynamic payload type 96:
ismacryp && rtp.p_type==96
You cannot directly filter ISMACryp protocol while capturing, but you can, for example, filter a given UDP port YYY:
udp port YYY
http://www.isma.tv Internet Streaming Media Alliance (ISMA) main page.
http://www.isma.tv/specreq.nsf/SpecRequest Technical specifications available here upon request, free of charge.
http://en.wikipedia.org/wiki/ISMACryp Wikipedia entry.