How do you put a TV station on the Mbone?

George Bonser gbonser at
Thu May 5 05:55:54 UTC 2011

> > There is a security aspect to such things, though, as how do you
> > the content is from a trusted source?  That is the bugaboo with
> > multicast.  It needs to be information that isn't going to hurt
> anything
> > if it is bogus.  Also, it opens up a DoS possibility with noise
> traffic
> > sent to the multicast group.
> SSM with encryption?

Well, certainly, but source address can be very easily spoofed with a
UDP multicast stream.  Now that could be mitigated with a lot of network
configuration rules but something is needed that just works without all

So using multicast for things like software updates to computers over
the general internet to the general public probably isn't going to work.
Encryption is also an issue because it doesn't really work well over
multicast. How do I encrypt something in a way that anyone can decrypt
but nobody can duplicate?  If I have a separate stream per user, that is
easy.  If I have one stream for all users, that is harder.  The answer
is probably in some sort of digital signature but not really encryption.

Using public/private key encryption over multicast, I would have to
distribute the private key so others could decrypt the content.  If they
have the private key, they can generate a public key to use to generate

Encryption is probably overkill anyway.  What is needed is a mechanism
simply to say that the content is certified to have come from the source
it claims to come from.  So ... basically ... better not to use
multicast for anything you really might have any security issues with.
Fine for broadcasting a video, not so fine for a kernel update.

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