From 5c6b282e57f866a1341eb705cb21507fcbfcc543 Mon Sep 17 00:00:00 2001 From: Ian Jackson Date: Mon, 6 Feb 2023 12:25:55 +0000 Subject: Call the key in desc-auth-ephemeral-key, KP_hs_desc_ephem Proposed by @nickm in https://gitlab.torproject.org/tpo/core/arti/-/merge_requests/999/diffs#50f9790ab3f0a65f7ac3e4f413c84f51fae1f855_0_26 (I think the spec is not 100% clear that hs_y and hs_Y are *this* key, rather than some other possible ephemeral keypair the HS might have, so please would the reviewer check that this is actually true.) --- rend-spec-v3.txt | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/rend-spec-v3.txt b/rend-spec-v3.txt index a8ac264..afc2a46 100644 --- a/rend-spec-v3.txt +++ b/rend-spec-v3.txt @@ -1208,7 +1208,7 @@ Table of contents: If client authorization is disabled, the value here should be "x25519". - "desc-auth-ephemeral-key" SP key NL + "desc-auth-ephemeral-key" SP KP_hs_desc_ephem NL [Exactly once] @@ -1239,13 +1239,11 @@ Table of contents: client_x = private x25519 key of authorized client client_X = public x25519 key of authorized client - hs_y = private key of ephemeral x25519 keypair of hidden service - hs_Y = public key of ephemeral x25519 keypair of hidden service descriptor_cookie = descriptor cookie used to encrypt the descriptor And here is what the hidden service computes: - SECRET_SEED = x25519(hs_y, client_X) + SECRET_SEED = x25519(KS_hs_desc_ephem, client_X) KEYS = KDF(N_hs_subcred | SECRET_SEED, 40) CLIENT-ID = fist 8 bytes of KEYS COOKIE-KEY = last 32 bytes of KEYS -- cgit v1.2.3-54-g00ecf From 7b3d7a40a0ac8f59b9f6d79205dfc53de4168f0c Mon Sep 17 00:00:00 2001 From: Ian Jackson Date: Mon, 6 Feb 2023 12:51:41 +0000 Subject: Use proper names for KP_hsc_desc_enc --- rend-spec-v3.txt | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/rend-spec-v3.txt b/rend-spec-v3.txt index afc2a46..805e0d9 100644 --- a/rend-spec-v3.txt +++ b/rend-spec-v3.txt @@ -1231,19 +1231,17 @@ Table of contents: When client authorization is enabled, each "auth-client" line contains the descriptor cookie encrypted to each individual client. We assume that - each authorized client possesses a pre-shared x25519 keypair which is - used to decrypt the descriptor cookie. + each authorized client possesses a pre-shared x25519 keypair + KS/KP_hsc_desc_enc which is used to decrypt the descriptor cookie. We now describe the descriptor cookie encryption scheme. Here are the relevant keys: - client_x = private x25519 key of authorized client - client_X = public x25519 key of authorized client descriptor_cookie = descriptor cookie used to encrypt the descriptor And here is what the hidden service computes: - SECRET_SEED = x25519(KS_hs_desc_ephem, client_X) + SECRET_SEED = x25519(KS_hs_desc_ephem, KP_hsc_desc_enc) KEYS = KDF(N_hs_subcred | SECRET_SEED, 40) CLIENT-ID = fist 8 bytes of KEYS COOKIE-KEY = last 32 bytes of KEYS -- cgit v1.2.3-54-g00ecf