[Privacy-pass] External verifiability: a concrete proposal

Watson Ladd <watsonbladd@gmail.com> Thu, 09 July 2020 21:46 UTC

Return-Path: <watsonbladd@gmail.com>
X-Original-To: privacy-pass@ietfa.amsl.com
Delivered-To: privacy-pass@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id B563D3A07A8 for <privacy-pass@ietfa.amsl.com>; Thu, 9 Jul 2020 14:46:07 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.099
X-Spam-Level:
X-Spam-Status: No, score=-2.099 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=gmail.com
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 76mHywMuxw-q for <privacy-pass@ietfa.amsl.com>; Thu, 9 Jul 2020 14:46:05 -0700 (PDT)
Received: from mail-lj1-x233.google.com (mail-lj1-x233.google.com [IPv6:2a00:1450:4864:20::233]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id D9E1A3A098A for <privacy-pass@ietf.org>; Thu, 9 Jul 2020 14:46:02 -0700 (PDT)
Received: by mail-lj1-x233.google.com with SMTP id e8so4128757ljb.0 for <privacy-pass@ietf.org>; Thu, 09 Jul 2020 14:46:02 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to; bh=7HUxEAsZ4y4QzO7a+XzNotx8dKMHIdr0Bk/uf+MH3tc=; b=ON8TFKNbiSZiM84gWU0M5oNDoksZlQTjzgNoS8/jkZ0mfdHbbOP67aGiJh4DmwhcLw 8HP1+o8WjEZp3PScidvQjpOE+ItSzhTO4zW9U1PjLkAbf9My5JC9dfRO/aJCd471IfwF GQtSkA+WwVTk81vWLnrZuEKdRbEOEJg8g4Jd6hcEO//z5H4GmwelKC08U2Yx6jKo9InV ZtmWCGGI9eVdut6G51Ew2Ik0GxR4Jhjrl06hyozj1fMwT2H/UopkagCegjgryUnRQfCE kQDvn7pQ+i9Waa1eWJddHe0m1Qy4NduXLuLNPUamBBl/FfLXPYDCDavKYxag+KdPUhQ0 m8fg==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to; bh=7HUxEAsZ4y4QzO7a+XzNotx8dKMHIdr0Bk/uf+MH3tc=; b=lIKSh4sedSYEyyB0mTgQg/8nJh1FknzEzdD2O2vYdjZpU17ouIgvouYxDjEHIvStnZ 35Sxj57/YYq29hItof8xLEZb6+upSIaIgQ6PSGeA6oo6xYhFW2l/Rd46rAu+0ONxXbvX 7NxnPeyk6gZ9fEA+KnszD2HnEz4Vuk3Wi+T69crD5KsUxXa5e1oI1JhLRtVo6C9B9pnN jNN1PDvSNRKIZNXK2Zlt4TAjwGXuaMMmmMvVcQtBZjIETdxqFj8/NTwTne7wf7TH8UV6 wAzEuRIP3kKrazsDCqmo2ByjBB45UaBajIQjBqm51j7yH1KL3T+UMlf+yN8NqXl62P/Q xjuQ==
X-Gm-Message-State: AOAM530Bm2Rb9U6XNbhnQCOlO725b+J6rPHcMqiC3fSXoltW9NUze+AU 8S8oL4ycyEDoD3Yw/UPEC/ur6pKItc4SLx97z/wD9BVx
X-Google-Smtp-Source: ABdhPJyTeK34QjAD4vK502fZeMPUORRaxsIgB4DIrqW4oduRF7Okz7lxjPjJI2sI/Sb4ei7rwEuq/tdEhdefwZZyGOI=
X-Received: by 2002:a2e:2a81:: with SMTP id q123mr38583271ljq.229.1594331160184; Thu, 09 Jul 2020 14:46:00 -0700 (PDT)
MIME-Version: 1.0
From: Watson Ladd <watsonbladd@gmail.com>
Date: Thu, 9 Jul 2020 17:45:49 -0400
Message-ID: <CACsn0c=KCcq27wEiVnkRritmuxYyR_mewwe48FBx1YnxZTu_aA@mail.gmail.com>
To: privacy-pass@ietf.org
Content-Type: text/plain; charset="UTF-8"
Archived-At: <https://mailarchive.ietf.org/arch/msg/privacy-pass/BDOOhSLwB3uUJcfBiss6nUF5sUA>
Subject: [Privacy-pass] External verifiability: a concrete proposal
X-BeenThere: privacy-pass@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: <privacy-pass.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/privacy-pass>, <mailto:privacy-pass-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/privacy-pass/>
List-Post: <mailto:privacy-pass@ietf.org>
List-Help: <mailto:privacy-pass-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/privacy-pass>, <mailto:privacy-pass-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 09 Jul 2020 21:46:08 -0000

Dear WG members,

Recently I heard of some interesting applications of privacy pass
where external verifiability would be essential. These applications
where ones where a central server was issuing tokens that various
others could use.

My concrete proposal is blind Boneh-Lynn-Shacham signatures.
Concretely we use G1, G2, GT a type III pairing, and have the key of
the issuer be kg_2. As in vanilla privacy pass the tokens are kH(x)
where x is a string and H is a hash function into G_1. However to
verify a token (y, x) one verifies the pairing equations e(y,
g_2)=e(H(x), kg_2). One could use the BLS12-381 parameter set for
this.

Sincerely,
Watson Ladd