New Bitcoin Core Update Rolls Out Various Changes

Bitcoin Core v0.12.1rc2 has been tagged on GitHub. This “minor version release” contains several updates to the Core protocol, “including the BIP9, BIP68 and BIP112 softfork, various bugfixes and updated translations.”

New Features on Bitcoin Core v0.12.1rc2

Bitcoin CoreReddit user Keystrike detailed the changes made from the previous version:

“Notable changes

“First version bits BIP9 softfork deployment

“This release includes a soft fork deployment to enforce BIP68, BIP112and [BIP113][] using the BIP9deployment mechanism.

“The deployment sets the block version number to 0x20000001 between midnight 1st May 2016 and midnight 1st May 2017 to signal readiness for deployment. The version number consists of 0x20000000 to indicate version bits together with setting bit 0 to indicate support for this combined deployment, shown as “csv” in thegetblockchaininfo RPC call.

“For more information about the soft forking change, please see

“This specific backport pull-request can be viewed at

“BIP68 soft fork to enforce sequence locks for relative locktime

“BIP68introduces relative lock-time consensus-enforced semantics of the sequence number field to enable a signed transaction input to remain invalid for a defined period of time after confirmation of its corresponding outpoint.

“For more information about the implementation, see

“BIP112 soft fork to enforce OP_CHECKSEQUENCEVERIFY

“BIP112redefines the existing OP_NOP3 as OP_CHECKSEQUENCEVERIFY (CSV) for a new opcode in the Bitcoin scripting system that in combination with BIP68allows execution pathways of a script to be restricted based on the age of the output being spent.

“For more information about the implementation, see

“BIP113 locktime enforcement soft fork

“Bitcoin Core 0.11.2 previously introduced mempool-only locktime enforcement using GetMedianTimePast(). This release seeks to consensus enforce the rule.

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“Bitcoin transactions currently may specify a locktime indicating when they may be added to a valid block. Current consensus rules require that blocks have a block header time greater than the locktime specified in any transaction in that block.

“Miners get to choose what time they use for their header time, with the consensus rule being that no node will accept a block whose time is more than two hours in the future. This creates a incentive for miners to set their header times to future values in order to include locktimed transactions which weren’t supposed to be included for up to two more hours.

“The consensus rules also specify that valid blocks may have a header time greater than that of the median of the 11 previous blocks. This GetMedianTimePast() time has a key feature we generally associate with time: it can’t go backwards.

“[BIP113][] specifies a soft fork enforced in this release that weakens this perverse incentive for individual miners to use a future time by requiring that valid blocks have a computed GetMedianTimePast() greater than the locktime specified in any transaction in that block.

“Mempool inclusion rules currently require transactions to be valid for immediate inclusion in a block in order to be accepted into the mempool. This release begins applying the BIP113 rule to received transactions, so transaction whose time is greater than the GetMedianTimePast() will no longer be accepted into the mempool.

“Implication for miners: you will begin rejecting transactions that would not be valid under BIP113, which will prevent you from producing invalid blocks when BIP113 is enforced on the network. Any transactions which are valid under the current rules but not yet valid under the BIP113 rules will either be mined by other miners or delayed until they are valid under BIP113. Note, however, that time-based locktime transactions are more or less unseen on the network currently.

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“Implication for users: GetMedianTimePast() always trails behind the current time, so a transaction locktime set to the present time will be rejected by nodes running this release until the median time moves forward. To compensate, subtract one hour (3,600 seconds) from your locktimes to allow those transactions to be included in mempools at approximately the expected time.

“For more information about the implementation, see


“The p2p alert system is off by default. To turn on, use -alert with startup configuration.”

Full Implementation?

Keystrike told Redditors that this new version “will be finalized soon, almost definitely this month.”

Reddit user sumBTC compiled and ran the new version, posting a link to Bitnodes for everyone to see.

To view the source code for Bitcoin Core v0.12.1rc2, you can visit this GitHub page.

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