[tor-dev] On picking Introduction Points in Next Generation Hidden Services

Christopher Baines cbaines8 at gmail.com
Tue Aug 12 18:07:28 UTC 2014

On 12/08/14 12:05, George Kadianakis wrote:
> One missing piece of rend-spec-ng.txt [0] is a section on how HSes
> should pick their Introduction Points (IPs). There are three main
> questions here:
> - How many IPs should an HS have?
> - Which relays can be IPs?
> - What's the lifetime of an IP?

There might be one additional question that you might want to consider
considering, that of reconnecting to introduction points? [1]

1: https://trac.torproject.org/projects/tor/ticket/8239

This functionality is required for the particular HS scaling
architecture discussed below.

>   Furthermore, as part of the Next Generation HSes initiative [0], we
>   are considering enhancing the availability of HSes by allowing
>   multiple nodes per Hidden Service. A plausible idea for achieving that
>   is to allow multiple IP circuits per Introduction Point, as explained
>   in [tor-dev] by Christopher Baines [1]. This means that IPs would work
>   like this:
>   https://people.torproject.org/~asn/hs/ip_placement_scaling.jpg
>   where HS_1, HS_2 and HS_3 are the various nodes of the HS.
>   This allows the IPs to launch the following attacks:
>   a) IPs can learn the number of nodes of an HS, by counting the number
>      of IP circuits on them. Also, the IPs can learn the prsense of the
>      nodes of an HS, by looking at the state of their circuit.
>   b) IPs can choose which HS node will receive traffic.

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