Bitcoin Core 32 enters final testing with faster validation, fee changes and security fixes

Bitcoin Core, the software used to run Bitcoin nodes, has moved its next major update into final testing with changes to transaction fees, block processing and the way wallets build transactions.

The first release candidate for Bitcoin Core 32.0 was tagged on Sept. 14, starting the final testing cycle before developers aim to release the finished version on Oct. 10, according to the project’s release schedule.

Bitcoin Core lets a computer independently check transactions and blocks against Bitcoin’s rules rather than relying on another service. Version 32 does not change those rules.

Bitcoin Core currently estimates how much a user should pay for a transaction largely by looking at the fees attached to transactions that made it into previous blocks. Version 32 adds a second estimator that looks at transactions currently waiting to be confirmed.

The software will compare the two and can recommend the lower fee when current network conditions support it. That should let estimates fall more quickly when congestion clears instead of continuing to reflect more expensive transactions from earlier blocks, according to the draft release notes.

Nodes can now fetch transaction data from their databases using several processing threads at once while checking blocks. Bitcoin Core will use eight of those threads by default, reducing time spent waiting for information stored on disk when a node is catching up with the blockchain.

Developers also fixed a flaw that had existed since Bitcoin Core 24.0 on non-Windows systems.

An authenticated user with permission to create wallets could give one a specially crafted name and, under certain conditions, cause commands to run on the computer hosting the node. The attack required the operator to have enabled walletnotify, a feature that automatically runs a chosen command when a wallet transaction occurs. Bitcoin Core 32 treats wallet names as literal text instead of allowing parts of the name to be interpreted as commands.

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Wallet changes and a memory flaw

Four Bitcoin Core commands used to create partially signed transactions will also start using the newer PSBT version 2 format by default. Those transactions are commonly passed between wallet software and signing devices before bitcoin is sent.

Applications can still request the older format, but services built directly around those Core commands will need to make sure they support version 2.