From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id B47E3D30 for ; Thu, 6 Sep 2018 15:16:57 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-ua1-f46.google.com (mail-ua1-f46.google.com [209.85.222.46]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id B3E947F9 for ; Thu, 6 Sep 2018 15:16:55 +0000 (UTC) Received: by mail-ua1-f46.google.com with SMTP id f4-v6so9034006uao.10 for ; Thu, 06 Sep 2018 08:16:55 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=dhEJ/pVrk8sPbg8UmQN9o3FAN6FmNQcIi+SWzO70O04=; b=Zlod6wUFHGpe1kYdDhqJxAa9L33kSKhPHa7dimO5RtHTE3qHfrD5z9EsBDafLUdWdO g3ajOc/9y2RjniYYi799BxnrUoiZhXH5hHQ34J77Np5YoClS5tCXDcaC7MMyFtlXddCJ D9fuTiqy8NPQBTeXQ0Ngrw79p+zMHyKUgmz+qlFNUoCQvEjlpBKeNjQ+qwBzusESF2wC V2nHSETNFnjeESBiOWyBq8toH39R0QptOtw+eKdQA1ru7izApVrfEdikE+2EIf6L/NCh +WYc2zbV5kXVxWIOaTKNSMYFFJc/das14BStP6RM0zBe4RQjmsWLq6x0KCYcV7hQfe9T MT0Q== X-Gm-Message-State: APzg51DlLn3BIOSX/XivURYzsIDvTQlkb+e3Zd1XRuAsvZWfF0rfUWi2 bQKCgwQdWRAn9onRVlFIVKXbffkLwOHqdoVLD9I= X-Google-Smtp-Source: ANB0Vdar3MTTVTuOQcvyF3lxeT4BS8BoBrFTebLWVZJXBKubmzYLRS9jZySASifaJl1xigwoPATIUFZ01rE6Pi9zK/Y= X-Received: by 2002:ab0:5594:: with SMTP id v20-v6mr1194597uaa.146.1536247014746; Thu, 06 Sep 2018 08:16:54 -0700 (PDT) MIME-Version: 1.0 References: <3d4162e0-1f8b-0f23-85fc-9d18d4352cae@gmail.com> In-Reply-To: <3d4162e0-1f8b-0f23-85fc-9d18d4352cae@gmail.com> From: Gregory Maxwell Date: Thu, 6 Sep 2018 15:16:34 +0000 Message-ID: To: a.ranchalpedrosa@gmail.com, Bitcoin Dev Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org X-Mailman-Approved-At: Thu, 06 Sep 2018 16:20:26 +0000 Cc: sara.tucci@cea.fr, Onder.GURCAN@cea.fr Subject: Re: [bitcoin-dev] A BIP proposal for transactions that are 'cancellable' 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, 06 Sep 2018 15:16:57 -0000 Functionality such as this does not currently exist not because no one thought of it before, but because it has been proposed many times before and determined to be harmful. The existing design of CLTV/CSV were carefully constructed to make it impossible for a transaction to go from valid to invalid based on the time. The most naive construction-- e.g. push the current time/height on the stack-- would have that property and was specifically avoided. When a spend goes from valid to invalid it means that a reorganization will destroy coins even completely absent any dishonest actions of the coins prior owner in the coins recent casual history. Effectively a coin with any kind of non-monotone validity event in its recent history functions like a recently generated coin: a coin that reorgs destroy. Bitcoin addresses the issue for recently generated coins by not permitting their use for 100 blocks. I've yet to see an argument for a use case for non-monotone validity that still sounds useful once the negative effects are addressed (e.g. by subjecting coins that have gone through them to a maturity limitation).