Hello everyone,

I am a researcher currently looking into different schemes for what you call 
Keyblinding in the rendevouz spec.

https://spec.torproject.org/rend-spec/keyblinding-scheme.html

I noticed that your description there mentiones a secret `s` to be hashed into 
the blinding factor, and have a few questions about it:

1. Is this secret currently being used / intended to be used? If so, how?

2. What kinds of security (formally or informally) would you expect from using 
a secret in the derivation process? For example, do you just require that 
someone without `s` cannot look up the service, or is this also meant as a way 
of ensuring that HSDir nodes cannot find correlations between services and 
descriptors (amounting to some sort of additional censorship resistance)?

The reason I am asking is because my research has identified some potentially 
post quantum secure schemes which for unknown identity keys results in 
uncorrelatable blinded keys, but where for known public keys you can 
efficiently determine whether a blinded key is its derivative, even if you do 
not know the blinding factor. I am wondering for which kinds of applications 
(with TOR being a major one) this would be relevant.

If you have any insights, please let me know. Also I am new to the TOR-Dev 
world, so feel free to send me to a different mailing list, should I have 
chosen the wrone one for this topic :)

Thanks in advance,
Thomas

-- 

```
M.Sc. Thomas Bellebaum
Applied Privacy Technologies
Fraunhofer Institute for Applied and Integrated Security AISEC

Lichtenbergstraße 11, 85748 Garching near Munich (Germany)
Tel. +49 89 32299 86 1039
thomas.belleb...@aisec.fraunhofer.de
https://www.aisec.fraunhofer.de

```
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