What is Communications Data?

[Ross Anderson]

> When I use my Internet banking service I provide my name, my date of 
> birth, a password, and some other personal information to authenticate 
> my access. This clearly constitutes data "identifying, or purporting to 
> identify, any person ... to or from which the communication [was] 
> transmitted". Would anyone contend this constitutes traffic data? Would 
> anyone contend that it is not part of the content of the communication?

It can be both. I go into this in chapter 6 of my book, where I
discuss the problems of naming in secure distributed systems. Stuff
that's a name at one level in the system can be an address at the
next. Similarly, stuff can be both content and traffic data.

This is nothing new. Years ago, there was argument in the USA about
content versus traffic - the FBI found it inconvenient that
`post-cut-through' digits were treated as content, and so a pen
register order isn't enough to find out whom someone was phoning with
a phone card - you need a wiretap warrant. (This is also in my book.)

> May I suggest we speak of "pure content" in future?

Even at the level of human protocols, that's hard. Suppose I send an
email saying `Hi, it was me who called you yesterday when you were
busy; if you want to call me back my office number's 123 4567 89'. 
That's pure content, but it's also sort-of traffic data, isn't it?

I expect things will keep on getting worse, as people will keep on
layering one protocol or service on top of another.

The import for the Home Office is this. If the regulations Simon's
working on are to remain effective and to continue to command
reasonably broad support, they will have to be updated regularly. This
is not a big deal - there are areas of government (such as export
controls) where regulations are reworked every year or two to keep up
with teachnology. However, the Home Office will have to acquire a team
that maintains institutional expertise and, presumably, carries on the
coversation on this list. It won't be enough for the Home Secretary of
the day to call for Simon whenever policy loses public credibility.

Simon, what say you?

Ross