Bitcoin-Qt version 0.8.1 released
18 March 2013

Bitcoin-Qt version 0.8.1 is now available from:

This is a maintenance release that adds a new network rule to avoid a chain-forking incompatibility with versions 0.7.2 and earlier.

Please report bugs using the issue tracker at GitHub.

How to Upgrade

If you are running an older version, shut it down. Wait until it has completely shut down (which might take a few minutes for older versions), then run the installer (on Windows) or just copy over /Applications/Bitcoin-Qt (on Mac) or bitcoind/bitcoin-qt (on Linux).

If you are upgrading from version 0.7.2 or earlier, the first time you run 0.8.1 your blockchain files will be re-indexed, which will take anywhere from 30 minutes to several hours, depending on the speed of your machine.

0.8.1 Release notes

The 0.8.1 release has just two changes from the 0.8.0 release:

  1. A new block-acceptance rule that will be enforced from 21 March 2013 until 15 May 2013 to prevent accepting blocks that fail to validate on pre-0.8 peers.

  2. A new compiled-in checkpoint at block number 225,430 – the first block of the 11 March 2013 chain fork.

0.8.0 Release notes

Incompatible Changes

This release no longer maintains a full index of historical transaction ids by default, so looking up an arbitrary transaction using the getrawtransaction RPC call will not work. If you need that functionality, you must run once with -txindex=1 -reindex=1 to rebuild block-chain indices (see below for more details).


Mac and Windows binaries are signed with certificates owned by the Bitcoin Foundation, to be compatible with the new security features in OSX 10.8 and Windows 8.

LevelDB, a fast, open-source, non-relational database from Google, is now used to store transaction and block indices. LevelDB works much better on machines with slow I/O and is faster in general. Berkeley DB is now only used for the wallet.dat file (public and private wallet keys and transactions relevant to you).

Pieter Wuille implemented many optimizations to the way transactions are verified, so a running, synchronized node uses less working memory and does much less I/O. He also implemented parallel signature checking, so if you have a multi-CPU machine all CPUs will be used to verify transactions.

New Features

“Bloom filter” support in the network protocol for sending only relevant transactions to lightweight clients.

contrib/verifysfbinaries is a shell-script to verify that the binary downloads at sourceforge have not been tampered with. If you are able, you can help make everybody’s downloads more secure by running this occasionally to check PGP signatures against download file checksums.

contrib/spendfrom is a python-language command-line utility that demonstrates how to use the “raw transactions” JSON-RPC api to send coins received from particular addresses (also known as “coin control”).

New/changed settings (command-line or bitcoin.conf file)

dbcache : controls LevelDB memory usage.

par : controls how many threads to use to validate transactions. Defaults to the number of CPUs on your machine, use -par=1 to limit to a single CPU.

txindex : maintains an extra index of old, spent transaction ids so they will be found by the getrawtransaction JSON-RPC method.

reindex : rebuild block and transaction indices from the downloaded block data.

New JSON-RPC API Features

lockunspent / listlockunspent allow locking transaction outputs for a period of time so they will not be spent by other processes that might be accessing the same wallet.

addnode / getaddednodeinfo methods, to connect to specific peers without restarting.

importprivkey now takes an optional boolean parameter (default true) to control whether or not to rescan the blockchain for transactions after importing a new private key.

Important Bug Fixes

Privacy leak: the position of the “change” output in most transactions was not being properly randomized, making network analysis of the transaction graph to identify users’ wallets easier.

Zero-confirmation transaction vulnerability: accepting zero-confirmation transactions (transactions that have not yet been included in a block) from somebody you do not trust is still not recommended, because there will always be ways for attackers to double-spend zero-confirmation transactions. However, this release includes a bug fix that makes it a little bit more difficult for attackers to double-spend a certain type (“lockTime in the future”) of zero-confirmation transaction.

Dependency Changes

Qt 4.8.3 (compiling against older versions of Qt 4 should continue to work)

Thanks to everybody who contributed to the 0.8.0 release:

  • Alexander Kjeldaas
  • Andrey Alekseenko
  • Arnav Singh
  • Christian von Roques
  • Eric Lombrozo
  • Forrest Voight
  • Gavin Andresen
  • Gregory Maxwell
  • Jeff Garzik
  • Luke Dashjr
  • Matt Corallo
  • Mike Cassano
  • Mike Hearn
  • Peter Todd
  • Philip Kaufmann
  • Pieter Wuille
  • Richard Schwab
  • Robert Backhaus
  • Rune K. Svendsen
  • Sergio Demian Lerner
  • Wladimir J. van der Laan
  • burger2
  • default
  • fanquake
  • grimd34th
  • justmoon
  • redshark1802
  • tucenaber
  • xanatos
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