From 72b0d977590e4cdc81608443b548e5a5276ad137 Mon Sep 17 00:00:00 2001 From: Christopher Wood Date: Fri, 16 Sep 2022 08:37:20 -0400 Subject: [PATCH] Add section on timing attacks Closes #191. cc @tfpauly, @nikitaborisov --- draft-ietf-privacypass-architecture.md | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/draft-ietf-privacypass-architecture.md b/draft-ietf-privacypass-architecture.md index a2082cb6..3c75c26a 100755 --- a/draft-ietf-privacypass-architecture.md +++ b/draft-ietf-privacypass-architecture.md @@ -728,7 +728,20 @@ hit: Output resp ~~~ -## Centralization +## Side-Channel Attacks + +Side-channel attacks, such as those based on timing correlation, could be +used to link attestation and redemption contexts together. In particular, +for interactive tokens that are bound to a Client-specific redemption +context, the anonymity set of Clients during the issuance protocol consists +of those Clients that started issuance between the time of the Origin's +challenge and the corresponding token redemption. Depending on the number +of Clients using a particular Issuer during that time window, the set can +be small. Appliations should take such side channels into consideration before +choosing a particular deployment model and type of token challenge and redemption +context. + +# Centralization A consequence of limiting the number of participants (Attesters or Issuers) in Privacy Pass deployments for meaningful privacy is that it forces concentrated