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 CB7688E2 for ; Wed, 24 Jan 2018 03:50:11 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-ot0-f172.google.com (mail-ot0-f172.google.com [74.125.82.172]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 795822C4 for ; Wed, 24 Jan 2018 03:50:11 +0000 (UTC) Received: by mail-ot0-f172.google.com with SMTP id f100so2441898otf.3 for ; Tue, 23 Jan 2018 19:50:11 -0800 (PST) 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=KJdIGLdiClOqFCtlWWIWHIXeYWqBPJ/uvG+sBfaJIpk=; b=FOrcy2+qEY6Y4ekjEg5SYcbSF6RsolApk3AxA9krJSsUYJxwoSxPt+A8HCLdi3Ch76 5GfyDR3r1epFWLODDTmlKYIQ4ZsU6kGieQi7YkTU3zghLmqWl15IvB/vdKNdAy0n5V1r ez32n74B+71WZpqBde1P6ISJ3NWDlUjmcelYgKV5VSe99Zd0WarHg2JNU2ZVkuAcUqHH E9+VlnXF/yi1F2T3s8Zb3Psh2U89DouBMFmRvEarGcAAUpyu87RbtSNV1uvA8IdZlSDl REGSlpVv7U9v5/sW3xq55oOPmWmS5G0S46bYIDLRuC4KG7OQbj9VtNMfe9wRMH8/JOzD RbnQ== 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=KJdIGLdiClOqFCtlWWIWHIXeYWqBPJ/uvG+sBfaJIpk=; b=cc6BXEUYXnN8CilKUpDdIK7hJEqPbtWAHgo7gQBokQ85MpiGgRFSaB6XK4Pk5HNLG2 uOZlSbONHh5XP4WUlXTpgBUtkE/f3wuL+dinABFUY/BKew0IYpPeY26VmJ7dToQXsFsT Q7gJHQkDU2Bf8Z2m6UpUTdFu+PXdAKIeJM2FGplPwLW4sx5p6slpaLk97EZ+cShO5UiN xTFebtn+lXfN5PnJiG/oW8YR/j3uZOdAb0Yg575dk73ttv83lNX690QpU8m4bpzy4Gjr 1Rp1joyoKi3H4D99qquyC4SUIuIwE7zIo2Y4ldyst9Be0JPS25ko4Vgxjre2QH3yZcpa j3gw== X-Gm-Message-State: AKwxytcuPm2zu43kaWeURnWB73cRJsK4Wup96Jo3p2j61EwqcJgFUi/I sFqsBlOVHbUZNC5a4xfGNVoPkUobqcqRD92VPw0= X-Google-Smtp-Source: AH8x224nKFREKn9Z2v9MdHJJQiXN2sPysuHDd5hVOaYawoj3Ziog3rbTrNnBSCHhqpIs0lpWesnq1lH1yAjGEldypEg= X-Received: by 10.157.25.44 with SMTP id j44mr8156111ota.111.1516765810563; Tue, 23 Jan 2018 19:50:10 -0800 (PST) MIME-Version: 1.0 Received: by 10.157.60.145 with HTTP; Tue, 23 Jan 2018 19:50:10 -0800 (PST) From: =?UTF-8?B?0JDRgNGC0ZHQvCDQm9C40YLQstC40L3QvtCy0LjRhw==?= Date: Wed, 24 Jan 2018 06:50:10 +0300 Message-ID: To: bitcoin-dev@lists.linuxfoundation.org Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, 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: Wed, 24 Jan 2018 04:22:39 +0000 Subject: [bitcoin-dev] Why is deriving public key from the signature not used in Segwit? 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: Wed, 24 Jan 2018 03:50:11 -0000 Greetings. I wanted to ask what was the rationale behind still having both public key and signature in Segwit witness? As is known for a while, the public key can be derived from the signature and a quadrant byte, a trick that is successfully used both in Bitcoin message signing algorithm and in Ethereum transaction signatures. The later in particular suggests that this is a perfectly functional and secure alternative. Leaving out the public key would have saved 33 bytes per signature, which is quite a lot. So, the question is - was there a good reason to do it the old way (security, performance, privacy, something else?), or was it something that haven't been thought of/considered at the time?