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[tor-commits] [torspec] 02/03: Describe identity-binding defense for intro-point POW
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dgoulet pushed a commit to branch main
in repository torspec.
commit 97c0c12f478edcd9cd72aedd318f117b9f161946
Author: Nick Mathewson <nickm@xxxxxxxxxxxxxx>
AuthorDate: Mon May 8 13:30:47 2023 -0400
Describe identity-binding defense for intro-point POW
---
proposals/327-pow-over-intro.txt | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/proposals/327-pow-over-intro.txt b/proposals/327-pow-over-intro.txt
index 1ecbe3b..8f17753 100644
--- a/proposals/327-pow-over-intro.txt
+++ b/proposals/327-pow-over-intro.txt
@@ -303,6 +303,12 @@ Status: Draft
PoW 'target' (see [REF_TARGET]). The client SHOULD NOT accept 'target' values
that will cause unacceptably long PoW computation.
+ The client uses a "personalization string" P equal to the following
+ nul-terminated ascii string: "Tor hs intro v1\0".
+
+ The client looks up `ID`, the current 32-byte blinded public ID
+ (KP_hs_blind_id) for the onion service.
+
To complete the PoW the client follows the following logic:
a) Client selects a target effort E, based on <suggested-effort> and past
@@ -310,8 +316,8 @@ Status: Draft
b) Client generates a secure random 16-byte nonce N, as the starting
point for the solution search.
c) Client derives seed C by decoding 'seed-b64'.
- d) Client calculates S = equix_solve(C || N || E)
- e) Client calculates R = ntohl(blake2b_32(C || N || E || S))
+ d) Client calculates S = equix_solve(P || ID || C || N || E)
+ e) Client calculates R = ntohl(blake2b_32(P || ID || C || N || E || S))
f) Client checks if R * E <= UINT32_MAX.
f1) If yes, success! The client can submit N, E, the first 4 bytes of
C, and S.
@@ -388,9 +394,9 @@ Status: Draft
exists.
b) Fail if N = POW_NONCE is present in the replay cache
(see [REPLAY_PROTECTION])
- c) Calculate R = ntohl(blake2b_32(C || N || E || S))
+ c) Calculate R = ntohl(blake2b_32(P || ID || C || N || E || S))
d) Fail if R * E > UINT32_MAX
- e) Fail if equix_verify(C || N || E, S) != EQUIX_OK
+ e) Fail if equix_verify(P || ID || C || N || E, S) != EQUIX_OK
f) Put the request in the queue with a priority of E
If any of these steps fail the service MUST ignore this introduction request
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