[tor-onions] Probably-stupid question about Circuit IDs

[Alec Muffett]

Hi All,

I'm just skimming Mahrud's patch at


https://github.com/mahrud/tor/commit/a81eac6d0c0a35adc6036e736565f4a8e2f806fd

...referenced from elsewhere, and also from the blog post:

https://blog.cloudflare.com/cloudflare-onion-service/

Luckily for us, the IPv6 space is so vast that we can encode the Tor
> circuit number as an IP address in an unused range and use the Proxy
> Protocol to send it to the server. Here is an example of the header that
> our Tor daemon would insert in the connection:


...and it makes me wonder how far back up the chain of hops towards the
client, that the circuit ID is visible to a malicious relay? Is it
mostly-hidden several onion-skins down? I presume it's not trackable all
the way from the client's guard?

Am thinking about the necessary scope for a correlation attack.

    -a

-- 
http://dropsafe.crypticide.com/aboutalecm
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