[tor-relays] Need Routing Info on Relays

Derric Atzrott datzrott at alizeepathology.com
Thu Oct 9 19:50:28 UTC 2014

Hash: SHA1

> I am trying to figure out how the packet flows over a Tor network.. There is
> a mix of information.. Some claim that the ISP is not aware of the payload as
> the complete data is encrypted whereas some say that your ISP is not used at
> all when using Tor network. AFAIK my packets go to the outer web via my ISP
> and there is no way to by pass that. I might be wrong. Can someone give me a
> detailed packet flow?

I'll take a stab at this and someone else can correct my possibly wrong
and definitely simplified explaination.

We are going to use a packet is an envelope/postcard metaphor.  So imagine
that you are trying to communicate with Google.  Your computer usually just
takes that message throws it into an envelope and sends it to Google,
with your ISP representing the post office.  Because the data is
unencrypted, this envelope is actually more like a postcard.

Using Tor things are a little bit different.  You have a list of your
1,000 closest friends (exit nodes).  You randomly select three of them
(lets call them Alice, Bob, and Charles).  You take your message that
you are sending to Google and put it on a postcard.  Then you take that
postcard and put it in an envelope and address this outer envelope
to Charles.  You then seal it with a glue that only Charles can lick to
open (encryption).  You take that envelope destined for Charles and you
repeat the previous process, except this time you address it to Bob
(again with the special glue).  You do this one more time using an
envelope destined for Alice.

You then give that envelope to the mailman (your ISP).  Because the
list of Tor nodes is public and the protocol is well known, you ISP
knows that you are using Tor and knows that Alice is the first person
you are talking to.  Alice can only open her envelope and see a message
to Bob, so she knows you are using Tor and that she is to expect a reply
via Bob at some point.  Bob, when he opens his envelope, knows only that
someone somewhere is using Tor and that they sent their message to Alice
and that he has to send it to Charles.  Charles knows that someone somewhere
is using Tor and they want to send a postcard to Google.  Google knows
someone is using Tor and wanted to talk to them.

To get Google's reply back to you the process is repeated but in reverse.

Did that help at all?

Thank you,
Derric Atzrott
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