Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 4E08986A for ; Sat, 1 Sep 2018 17:27:08 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-wr1-f50.google.com (mail-wr1-f50.google.com [209.85.221.50]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 9C065A8 for ; Sat, 1 Sep 2018 17:27:07 +0000 (UTC) Received: by mail-wr1-f50.google.com with SMTP id w11-v6so13957196wrc.5 for ; Sat, 01 Sep 2018 10:27:07 -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 :content-transfer-encoding; bh=19GSTAHWdCM7c3jgKznFSGESgVZ4NhraOaFKVQTg/BY=; b=EDPDPd2wehF2KQylrTM3H6xYCDl0lVClXpXrVRhCpiNBdMESVM/PT78rZmg67ygejc EARIF/ZsLrxqXrTGv0NYRwzk0NsWQjB4v4hPKtCC6TFY1Agq1RqDGFwIKYjr6rsBRMB+ W4T/D0TEGGlyFmbCng+VAumH2o8CUlP+OfZxzUhFdW9OWCPYa9GlNQ+uhQWDbvlohkoT KEUAYuyTP4Nck9NwQQHaeLtLzokZtOd24KNSSWV+foRUiG2xMkapDMajvw7s9upKWNaj bPTxEqzl8zZ8t6wZcSVCQYdJe87+6vXR9/ZtxP9kLD1k69EG9VDnyJeOPoV3AffLRFIG IuQQ== 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 :content-transfer-encoding; bh=19GSTAHWdCM7c3jgKznFSGESgVZ4NhraOaFKVQTg/BY=; b=bJhSUNavGwk7KMTnWr81XXW5q75WE2TOntFZK3iJuyp0wGWgQFIdWzHLaM8jQOeoqj fEA1JSiuXfz9uo8qDkt2kMrgLzzVEapWAf0miVbrE2LL0o+xuBQcjwwWrIFdOQ0iDdJU baeH1JvfEIa6mVvMXjNErZlRwA6jogJ05bHH4uh6uHGA/HXBbrGkt647HYXpo6ptSRZV 4xh7SwSIaOicbynWx+DDB1SY1cin45F3i4fUGa7tAFPnnXpiUEkXL/VcLr9bdvYl/bX5 lMe6+NEiqEeZqYhJGvcRqI1PlNouiFuvzNVrS+V6hqApkYuTVGvYum1G9CY7E0b7F2r2 dF9w== X-Gm-Message-State: APzg51AN0X+cubMJeno4cEgspQ1h4IWvlqmMs0Wn5Ku/+GDEkEE3USv+ +1X0pndVkpAB3TgGHZovz+8PK2nS8/p4QKNkH79VP5fX X-Google-Smtp-Source: ANB0VdZkcaTodllno8eDK7J2aEpYj2xXllhwKHE07TuGolXL/YWy1ZejomCgQC9FfD6ZJhVS/+jZsVehqoiyUIYtYWk= X-Received: by 2002:adf:e648:: with SMTP id b8-v6mr14950454wrn.254.1535822826015; Sat, 01 Sep 2018 10:27:06 -0700 (PDT) MIME-Version: 1.0 From: Ruben Somsen Date: Sun, 2 Sep 2018 02:26:54 +0900 Message-ID: To: bitcoin-dev@lists.linuxfoundation.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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: Mon, 03 Sep 2018 23:25:52 +0000 Subject: [bitcoin-dev] Guiding transaction fees towards a more censorship resistant outcome 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: Sat, 01 Sep 2018 17:27:08 -0000 When a user creates a transaction with a fee attached, they are incentivizing miners to add this transaction to the blockchain. The task is usually not very specific -- as long as it ends up in a valid chain with the most Proof-of-Work, miners get paid. The payment is an incentive for miners to act in the way that users desire. To the user, there=E2=80=99s an individual benefit: their transaction gets added. To the network, there=E2=80=99s a shared benefit: all fees add to th= e security of other transactions in the chain. Miners can choose to ignore the incentives, but they would be leaving money on the table (and eventually get replaced by more competitive miners). Transactions from Bitcoin Core are slightly more specific about what they ask miners to do. Every transaction is only valid at a block height that is one higher than the last block. This incentivizes miners to build on top of the last block, instead of going back and reorganizing the blockchain. This is especially important in a future scenario where the fee reward is larger than the block reward. BIP 115* by Luke-jr is even more specific. It enables users to create transactions which are only valid if they are mined on top of a specific block. While originally designed as a form of replay protection, it actually serves as a deterrent for miners to reorganize the blockchain. If they orphan a block, it will invalidate transactions that demanded the inclusion of the orphaned block. This increases the cost of intentionally reorganizing the blockchain. Coinjoin**, the act of combining payments of multiple users into a single transaction, can be seen as yet another method for users to be more specific. The fate of their payments are now intertwined with that of others. If miners wish to censor a single payment, they have to reject the entire transaction, and the associated fee amount. Techniques like mimblewimble simplify this process, by making coinjoin non-interactive. This brings us to a theoretical scenario where: - every block contains only a single coinjoin transaction - the validity of this transaction depends on the inclusion of a specific previous block - the block reward is negligible compared to transaction fees In this scenario, if miners wish to undo a specific transaction that happened two blocks ago, they would have to create three empty blocks (receiving negligible compensation) in order to overtake the longest chain. And even then, users can still refuse to let their new transactions be mined on top of the empty blocks, disincentivizing such behavior completely. While not easy to achieve in practice (e.g. resolving natural forks becomes more complicated), it demonstrates that users can become more empowered than they are today, benefitting censorship resistance***. It is this line of thinking that I wish to convey. Perhaps it may inspire further ideas in this direction. -- Ruben Somsen * BIP 115: https://github.com/bitcoin/bips/blob/master/bip-0115.mediawiki ** Coinjoin: https://bitcointalk.org/index.php?topic=3D279249.0 *** Risk sharing principle: https://github.com/libbitcoin/libbitcoin/wiki/Risk-Sharing-Principle