Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 8AA69B62 for ; Thu, 28 Sep 2017 00:58:32 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-ua0-f175.google.com (mail-ua0-f175.google.com [209.85.217.175]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 1C93B3D5 for ; Thu, 28 Sep 2017 00:58:32 +0000 (UTC) Received: by mail-ua0-f175.google.com with SMTP id v12so5812uaf.5 for ; Wed, 27 Sep 2017 17:58:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to; bh=SmlEGfbkgO6YG1z93EkMWcMRdz25KC+jKnn/4pQxly8=; b=WnrM7AWDW+f3IyIfwgyq2e/lofjg8ifLIqRKDed7BeIb7arvGiW16d2l+WJq+1pSZO M2QJ4MhDJ3UpTXiQ/LVwGJix0Q4XaxT9eO/EXyI6Fdp6OXwO442NHWHZXYw7CKVyCjy/ vqj++be9LRix1t+WdEU6fLsli8Uazp0bJO3Zd4Yw9AF5BA3xt6v8UOTHzMxp2YhxAaWo Xd1O/nbHViudfvP9Ow1E6L0OI2pP2Ab3c9qUHyPx95TmF4lhq3oy21YsmpGCLIC9NU+P 3Ji4A03ascYkbqFXQnBVk0haoCp3UAriz38j8Qg0/YBk9FmBMH2U2peXQK5NpsqlfhMs BjCA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to; bh=SmlEGfbkgO6YG1z93EkMWcMRdz25KC+jKnn/4pQxly8=; b=AH3d+0V5tL5Dzz+vR+64nNn60BY+C4eRDgzt5BUOA+r6QdZ9tzU51bRlyU7HKSVO94 VB8y/Q9Heb3S30bQQY0OvXK46p8iL9TESJfLzddzTkCZD35w4nVhsir5MA2CZvkiZ9Mu MsXK9LNIlnmLfzB3UI6NRqq5IXqBjslyKBTTpKy1dGN0HojIrvqqCJSfOKiqA+6XZf6w rVMceOMF9EL6H30/CNsnBhV0/vcexkQeXK1mKoci0YrGCxxWZRRNvbbAZPRlOVm2yfBz wiXTHs9Nz2DeX6km/RWqCsHpBGPsTOFRfyJZrLFpqFelQNNx+/XawzCClMdF22vSoCol tqOg== X-Gm-Message-State: AMCzsaULDNs3Y7gnf1MvYt+Az7Txo2iFFZ3cropwLp36iQYpgdYKG2eZ 92n3sXJiF3ezqP/FcaiaejQ4l4ubsu1DuKI/HFo= X-Google-Smtp-Source: AOwi7QC7X6p0g1xxUpdD6FpNIlOGiKgmQ6Ir/z2kedSiUNx0SEDydprpFQclll9ljGIzJKf8+sCmFKX9JIDJ0sjY6pY= X-Received: by 10.176.21.109 with SMTP id p42mr2179606uae.127.1506560311280; Wed, 27 Sep 2017 17:58:31 -0700 (PDT) MIME-Version: 1.0 Sender: gmaxwell@gmail.com Received: by 10.103.146.78 with HTTP; Wed, 27 Sep 2017 17:58:30 -0700 (PDT) In-Reply-To: <20170927160654.GA12492@savin.petertodd.org> References: <20170927160654.GA12492@savin.petertodd.org> From: Gregory Maxwell Date: Thu, 28 Sep 2017 00:58:30 +0000 X-Google-Sender-Auth: krNz3z54X8tE8f1A8q5Q6psu608 Message-ID: To: Peter Todd , Bitcoin Protocol Discussion Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=0.5 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, FREEMAIL_FROM, RCVD_IN_DNSWL_NONE, RCVD_IN_SORBS_SPAM autolearn=disabled version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Subject: Re: [bitcoin-dev] Address expiration times should be added to BIP-173 X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 28 Sep 2017 00:58:32 -0000 On Wed, Sep 27, 2017 at 4:06 PM, Peter Todd via bitcoin-dev wrote: > Re-use of old addresses is a major problem, not only for privacy, but also > operationally: services like exchanges frequently have problems with users > sending funds to addresses whose private keys have been lost or stolen; there When Pieter and I were working on Bech32 we specifically designed for error correcting codes that had good performance for longer lengths than we technically needed specifically to incorporate things like dates and explicit amounts. (explicit amounts so that typos and bit flips in amounts displayed or in memory couldn't result in sending the wrong amount) But we also thought that also adding those features at the same time would retard adoption-- both due to debating over the encodings and because handling would result in different software requirements and layering, so you couldn't just drop them in. Doubly unfortunately, people have even deployed BIP173 already (prior to it even having much peer review or being adopted by its own authors), so I think a rethink now wouldn't be timely (I mean as a replacement to BIP173 rather than an additional format). :( But I do support the idea. One thing to keep in mind is that address format linked fields are most efficient if they're multiples of 5 bits. Perhaps use 1 bit to indicate an embedded amount and 19 bits of 1 day precision, resulting in a 1435 year span. Keep in mind that high precision of the expiration times is asking the sender to have a higher precision of idea of the time, date only is kinda nice. I think shorter expiration times are unlikely to be useful due to clock skew-- you can't assume a signer has any access to the Bitcoin network at all.