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Re: OT - Telephone Caller ID

2004-11-24 12:54:08
william(at)elan.net wrote:

On Sun, 21 Nov 2004, Seth Goodman wrote:

There is no point in forging Caller-ID in order to fool marketers or the
like. They do not use caller-ID, they never have. The marketers
have always used AID which like Caller-ID provides the source of the call,
unlike Caller-ID it cannot be blocked, you do have to have a direct trunk
connection however and you have to do some translation to get a telephone
number from the line id.
I didn't know about that.  At home, I never answer when the caller ID is
blocked.  At work, I still get a fair number of calls with no caller-ID
information.  Since a few of the cell-phone originated calls I get from
customers have no caller-ID information, for whatever reason, I have to
answer them all.  (I suppose I could let the voice mail system take these
calls.)  Some of these calls without caller-ID information turn out to be
marketing companies, so they are obviously not using the alternative system
you mentioned.  Is that currently against the law?  Is it different because
it is a business rather than residential?

You did not understand. AID is not for hiding/displaying your own caller id information, its interface to telco information that used so that one CLEC (telephone company) can tell the other CLECs where the call came from. It provides information on which telephone exchange call originated
(and this can be translated into NPA/NXX), type of circuit the call came
from and circuit id (well, its not exactly circuit id, its more of circuit
routing id). This id is not the same as your real telephone number but many telcos do not use "unique" enough schemes and so it might be possible to guess what phone number it was. In reality AID is as I mentioned routing information so think of it as ip address if your phone number is host name.
The key issue is that ANI was never intended to be safe from in-transit manipulations. There are no mechanisms to ensure the authenticity of the ANI digits. The "authenticity" was sufficiently ensured when only phone companies controlled the in-transits switches. However the scene has totally changed these days and ANI has not. The only way to be able to ensure the integrity of the ANI digits (or other such mechanism that identifies the caller) would be a cryptographic hash. This is just another legacy telephony element that will need to mature for the new telephony.

Doug

--*--
This 'telephone' has too many shortcomings to be seriously considered as a means of communication.
-Western Union internal memo, 1876.
--*--


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