[tor-dev] Notes on HS revamping

[George Kadianakis]

Hey Nick,

these are my notes from when I was writing the HS blog post. I updated
them a bit with some more stuff.

Might be helpful :)

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HS improvements:

1 performance 
    1.1 reuse IPs (#8239) 
    1.2 torperf (#8510) 
    1.3 scaling https://lists.torproject.org/pipermail/tor-dev/2013-October/005556.html 
    1.4 valet nodes 
    1.5 lasse's "Improving Efficiency and Simplicity of Tor circuit establishment and hidden services" 
        1.5.1 big design change. maybe worth it. assumes valet nodes IIRC 
2 security 
    2.1 Crypto upgrade 
        2.1.1 Upgrade id keys 
            [https://lists.torproject.org/pipermail/tor-dev/2013-October/005536.html]
            [https://lists.torproject.org/pipermail/tor-dev/2013-October/005534.html]
        2.1.2 Upgrade IP service keys 
        2.1.3 Fix hybrid encryption (?) 
    2.2 Onion anti-harvesting (#8106) https://lists.torproject.org/pipermail/tor-dev/2013-October/005534.html 
    2.3 Guard node enumeration (#9001) 
        2.3.1 Virtual Circuits? Guard tiers? 
    2.4 Unpredictable HSDirs (#8244) 
    2.5 Hide HS popularity 
        2.5.1 Oblivious transfer for HSDirs (is it needed if we have #8106? maybe yes.) 
        2.5.2 Unlinkable introductions in IPs (is this even possible?) (do we even care? we have service keys) 
3 Can we decrease the responsibility of guard nodes? It seems that security of HSes == their guard nodes, atm. 
    3.1 Implement stuff from https://blog.torproject.org/blog/improving-tors-anonymity-changing-guard-parameters 
    3.2 Add optional padding/bitrate anti-fingerprinting transport for HSes. 
        3.2.1 Can be enabled by truly paranoid HSes. 
        3.2.2 But this is going to make HSes stand out even more! 
        3.2.3 These transports can all be broken anyway. Except a truly slow but theoretically secure padding/constant bitrate transport. 
    3.3 What are other anonymous publishing protocols doing here? I2P seems to be weak here too, according to Grothoff's recent paper. 
4 misc 
    4.1 HSDirs system 
        4.1.1 Do we still need the hash ring even after #8106? 
        4.1.2 Look into Valet nodes 
    4.2 petnames/human memorable onions? 
        4.2.1 maybe better as a third party (probably unofficial) plugin to tor/firefox 
    4.3 Read and compare with other HS-like designs. See: 
        4.3.1 I2P, GNUNet, rewebber, retroshare, "Anonymizing censorship resistant systems" by Serjantov, ... 
        4.3.2 Check uni-directional tunnels of I2P and their pros/cons. 
        4.3.3 http://freehaven.net/anonbib/ 
    4.4 Encrypted servives https://gitweb.torproject.org/torspec.git/blob/HEAD:/proposals/ideas/xxx-encrypted-services.txt
5 What else should we do? How would we design HSes if we were not prejudiced by the current design?

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