[tor-bugs] #33650 [Core Tor/Tor]: Verify that intro2 cell extensions actually work

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#33650: Verify that intro2 cell extensions actually work
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 Reporter:  arma                                 |          Owner:
                                                 |  mikeperry
     Type:  task                                 |         Status:
                                                 |  accepted
 Priority:  Medium                               |      Milestone:
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-dos tor-dos-2020 anonymous-      |  Actual Points:
  credentials research                           |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by arma):

 Another piece of this ticket: let's discover how much extra space we
 actually have, in the cells, for these blobs.

 In particular, if we want to include a blob for the intro point and also a
 blob for the service, then these two will compete with each other for the
 limited space.

 And that realization opens up two directions for future research:

 * Space-compact tokens. For example, are there proof-of-work schemes where
 the proof can be communicated in very few bytes, yet it is still efficient
 for the checker to check it? As one example, I can imagine a scheme where
 you send only (x, y) where x is a short seed and y is a number of bytes
 you generate from that seed such that, when you hash the y bytes, you get
 the property you want. Thus the checker can just expand the y bytes and
 check the property, but the prover has to find an x and y that achieves
 the property. I just made that scheme up, and I bet other people have done
 it way better (i.e. more compact and/or more efficient for the verifier).

 * "Wide" intro cells. In the general case, we'll want to be able to send
 more than 100-200 bytes of tokens in these cells. So we'll want some way
 to send big cells, or to send multiple cells that are conceptually tied
 together. See proposal 249 ("Allow CREATE cells with >505 bytes of
 handshake data") for ideas that can hopefully be reused here.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/33650#comment:9>
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