Merge pull request bitcoin#501 from shaolinfry/bip-segwit-flagday

BIP 148: Mandatory activation of segwit deployment

Author: luke-jr

README.mediawiki

@@ -638,6 +638,13 @@ Those proposing changes should consider that ultimately consent may rest with th
 | Standard
 | Draft
 |-
+| [[bip-0148.mediawiki|148]]
+| Consensus (soft fork)
+| Mandatory activation of segwit deployment
+| Shaolin Fry
+| Standard
+| Draft
+|-
 | [[bip-0150.mediawiki|150]]
 | Peer Services
 | Peer Authentication

bip-0148.mediawiki

@@ -0,0 +1,74 @@
+<pre>
+  BIP: 148
+  Layer: Consensus (soft fork)
+  Title: Mandatory activation of segwit deployment
+  Author: Shaolin Fry <[email protected]>
+  Comments-Summary: No comments yet.
+  Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0148
+  Status: Draft
+  Type: Standards Track
+  Created: 2017-03-12
+  License: BSD-3-Clause
+           CC0-1.0
+</pre>
+
+==Abstract==
+
+This document specifies a BIP16 like soft fork flag day activation of the segregated witness BIP9 deployment known as "segwit".
+
+==Definitions==
+
+"existing segwit deployment" refer to the BIP9 "segwit" deployment using bit 1, between November 15th 2016 and November 15th 2017 to activate BIP141, BIP143 and BIP147.
+
+==Motivation==
+
+Segwit increases the blocksize, fixes transaction malleability, and makes scripting easier to upgrade as well as bringing many other [https://bitcoincore.org/en/2016/01/26/segwit-benefits/ benefits].
+
+It is hoped that miners will respond to this BIP by activating segwit early, before this BIP takes effect. Otherwise this BIP will cause the mandatory activation of the existing segwit deployment before the end of midnight November 15th 2017.
+
+==Specification==
+
+All times are specified according to median past time.
+
+This BIP will be activate between midnight October 1st 2017 (epoch time 1506816000) and midnight November 15th 2017 (epoch time 1510704000) if the existing segwit deployment is not activated before epoch time 1506816000. This BIP will cease to be active when the existing segwit deployment activates.
+
+While this BIP is active, all blocks must set the nVersion header top 3 bits to 001 together with bit field (1<<1) (according to the existing segwit deployment). Blocks that do not signal as required will be rejected.
+
+=== Reference implementation ===
+
+<pre>
+// mandatory segwit activation between Oct 1st 2017 and Nov 15th 2017 inclusive
+if (pindex->GetMedianTimePast() >= 1506816000 && pindex->GetMedianTimePast() <= 1510704000 && !IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) {
+    if (!((pindex->nVersion & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS) && (pindex->nVersion & VersionBitsMask(params, Consensus::DEPLOYMENT_SEGWIT)) != 0) {
+        return state.DoS(0, error("ConnectBlock(): relayed block must signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
+    }
+}
+</pre>
+
+https://github.com/bitcoin/bitcoin/compare/master...shaolinfry:bip-segwit-flagday
+
+==Backwards Compatibility==
+
+This deployment is compatible with the existing "segwit" bit 1 deployment scheduled between midnight November 15th, 2016 and midnight November 15th, 2017.
+
+==Rationale==
+
+Historically, the P2SH soft fork (BIP16) was activated using a predetermined flag day where nodes began enforcing the new rules. P2SH was successfully activated with relatively few issues
+
+By orphaning non-signalling blocks during the last month of the BIP9 bit 1 "segwit" deployment, this BIP can cause the existing "segwit" deployment to activate without needing to release a new deployment.
+
+==References==
+
+*[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-March/013714.html Mailing list discussion]
+*[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#L1281-L1283 P2SH flag day activation]
+*[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
+*[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
+*[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
+*[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for Version 0 Witness Program]]
+*[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element malleability]]
+*[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit benefits]
+
+==Copyright==
+
+This document dual licensed as BSD-3-Clause and CC0-1.0.
+