Bitcoin Core version 0.11.0 is now available from:

  <https://bitcoin.org/bin/bitcoin-core-0.11.0/>

This is a new major version release, bringing both new features and
bug fixes.

Please report bugs using the issue tracker at github:

  <https://github.com/bitcoin/bitcoin/issues>

Upgrading and downgrading
=========================

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).

Downgrade warning
------------------

Because release 0.10.0 and later makes use of headers-first synchronization and
parallel block download (see further), the block files and databases are not
backwards-compatible with pre-0.10 versions of Bitcoin Core or other software:

* Blocks will be stored on disk out of order (in the order they are
received, really), which makes it incompatible with some tools or
other programs. Reindexing using earlier versions will also not work
anymore as a result of this.

* The block index database will now hold headers for which no block is
stored on disk, which earlier versions won't support.

If you want to be able to downgrade smoothly, make a backup of your entire data
directory. Without this your node will need start syncing (or importing from
bootstrap.dat) anew afterwards. It is possible that the data from a completely
synchronised 0.10 node may be usable in older versions as-is, but this is not
supported and may break as soon as the older version attempts to reindex.

This does not affect wallet forward or backward compatibility. There are no
known problems when downgrading from 0.11.x to 0.10.x.

Important information
======================

Transaction flooding
---------------------

At the time of this release, the P2P network is being flooded with low-fee
transactions. This causes a ballooning of the mempool size.

If this growth of the mempool causes problematic memory use on your node, it is
possible to change a few configuration options to work around this. The growth
of the mempool can be monitored with the RPC command `getmempoolinfo`.

One is to increase the minimum transaction relay fee `minrelaytxfee`, which
defaults to 0.00001. This will cause transactions with fewer BTC/kB fee to be
rejected, and thus fewer transactions entering the mempool.

The other is to restrict the relaying of free transactions with
`limitfreerelay`. This option sets the number of kB/minute at which
free transactions (with enough priority) will be accepted. It defaults to 15.
Reducing this number reduces the speed at which the mempool can grow due
to free transactions.

For example, add the following to `bitcoin.conf`:

    minrelaytxfee=0.00005 
    limitfreerelay=5

More robust solutions are being worked on for a follow-up release.

Notable changes
===============

Block file pruning
----------------------

This release supports running a fully validating node without maintaining a copy 
of the raw block and undo data on disk. To recap, there are four types of data 
related to the blockchain in the bitcoin system: the raw blocks as received over 
the network (blk???.dat), the undo data (rev???.dat), the block index and the 
UTXO set (both LevelDB databases). The databases are built from the raw data.

Block pruning allows Bitcoin Core to delete the raw block and undo data once 
it's been validated and used to build the databases. At that point, the raw data 
is used only to relay blocks to other nodes, to handle reorganizations, to look 
up old transactions (if -txindex is enabled or via the RPC/REST interfaces), or 
for rescanning the wallet. The block index continues to hold the metadata about 
all blocks in the blockchain.

The user specifies how much space to allot for block & undo files. The minimum 
allowed is 550MB. Note that this is in addition to whatever is required for the 
block index and UTXO databases. The minimum was chosen so that Bitcoin Core will 
be able to maintain at least 288 blocks on disk (two days worth of blocks at 10 
minutes per block). In rare instances it is possible that the amount of space 
used will exceed the pruning target in order to keep the required last 288 
blocks on disk.

Block pruning works during initial sync in the same way as during steady state, 
by deleting block files "as you go" whenever disk space is allocated. Thus, if 
the user specifies 550MB, once that level is reached the program will begin 
deleting the oldest block and undo files, while continuing to download the 
blockchain.

For now, block pruning disables block relay.  In the future, nodes with block 
pruning will at a minimum relay "new" blocks, meaning blocks that extend their 
active chain. 

Block pruning is currently incompatible with running a wallet due to the fact 
that block data is used for rescanning the wallet and importing keys or 
addresses (which require a rescan.) However, running the wallet with block 
pruning will be supported in the near future, subject to those limitations.

Block pruning is also incompatible with -txindex and will automatically disable 
it.

Once you have pruned blocks, going back to unpruned state requires 
re-downloading the entire blockchain. To do this, re-start the node with 
-reindex. Note also that any problem that would cause a user to reindex (e.g., 
disk corruption) will cause a pruned node to redownload the entire blockchain. 
Finally, note that when a pruned node reindexes, it will delete any blk???.dat 
and rev???.dat files in the data directory prior to restarting the download.

To enable block pruning on the command line:

- `-prune=N`: where N is the number of MB to allot for raw block & undo data.

Modified RPC calls:

- `getblockchaininfo` now includes whether we are in pruned mode or not.
- `getblock` will check if the block's data has been pruned and if so, return an 
error.
- `getrawtransaction` will no longer be able to locate a transaction that has a 
UTXO but where its block file has been pruned. 

Pruning is disabled by default.

Big endian support
--------------------

Experimental support for big-endian CPU architectures was added in this
release. All little-endian specific code was replaced with endian-neutral
constructs. This has been tested on at least MIPS and PPC hosts. The build
system will automatically detect the endianness of the target.

Memory usage optimization
--------------------------

There have been many changes in this release to reduce the default memory usage
of a node, among which:

- Accurate UTXO cache size accounting (#6102); this makes the option `-dbcache`
  precise where this grossly underestimated memory usage before
- Reduce size of per-peer data structure (#6064 and others); this increases the
  number of connections that can be supported with the same amount of memory
- Reduce the number of threads (#5964, #5679); lowers the amount of (esp.
  virtual) memory needed

Fee estimation changes
----------------------

This release improves the algorithm used for fee estimation.  Previously, -1
was returned when there was insufficient data to give an estimate.  Now, -1
will also be returned when there is no fee or priority high enough for the
desired confirmation target. In those cases, it can help to ask for an estimate
for a higher target number of blocks. It is not uncommon for there to be no
fee or priority high enough to be reliably (85%) included in the next block and
for this reason, the default for `-txconfirmtarget=n` has changed from 1 to 2.

Privacy: Disable wallet transaction broadcast
----------------------------------------------

This release adds an option `-walletbroadcast=0` to prevent automatic
transaction broadcast and rebroadcast (#5951). This option allows separating
transaction submission from the node functionality.

Making use of this, third-party scripts can be written to take care of
transaction (re)broadcast:

- Send the transaction as normal, either through RPC or the GUI
- Retrieve the transaction data through RPC using `gettransaction` (NOT
  `getrawtransaction`). The `hex` field of the result will contain the raw
  hexadecimal representation of the transaction
- The transaction can then be broadcasted through arbitrary mechanisms
  supported by the script

One such application is selective Tor usage, where the node runs on the normal
internet but transactions are broadcasted over Tor.

For an example script see [bitcoin-submittx](https://github.com/laanwj/bitcoin-submittx).

Privacy: Stream isolation for Tor
----------------------------------

This release adds functionality to create a new circuit for every peer
connection, when the software is used with Tor. The new option,
`-proxyrandomize`, is on by default.

When enabled, every outgoing connection will (potentially) go through a
different exit node. That significantly reduces the chance to get unlucky and
pick a single exit node that is either malicious, or widely banned from the P2P
network. This improves connection reliability as well as privacy, especially
for the initial connections.

**Important note:** If a non-Tor SOCKS5 proxy is configured that supports
authentication, but doesn't require it, this change may cause that proxy to reject
connections. A user and password is sent where they weren't before. This setup
is exceedingly rare, but in this case `-proxyrandomize=0` can be passed to
disable the behavior.

0.11.0 Change log
=================

Detailed release notes follow. This overview includes changes that affect
behavior, not code moves, refactors and string updates. For convenience in locating
the code changes and accompanying discussion, both the pull request and
git merge commit are mentioned.

### RPC and REST
- #5461 `5f7279a` signrawtransaction: validate private key
- #5444 `103f66b` Add /rest/headers/<count>/<hash>.<ext>
- #4964 `95ecc0a` Add scriptPubKey field to validateaddress RPC call
- #5476 `c986972` Add time offset into getpeerinfo output
- #5540 `84eba47` Add unconfirmed and immature balances to getwalletinfo
- #5599 `40e96a3` Get rid of the internal miner's hashmeter
- #5711 `87ecfb0` Push down RPC locks
- #5754 `1c4e3f9` fix getblocktemplate lock issue
- #5756 `5d901d8` Fix getblocktemplate_proposals test by mining one block
- #5548 `d48ce48` Add /rest/chaininfos
- #5992 `4c4f1b4` Push down RPC reqWallet flag
- #6036 `585b5db` Show zero value txouts in listunspent
- #5199 `6364408` Add RPC call `gettxoutproof` to generate and verify merkle blocks
- #5418 `16341cc` Report missing inputs in sendrawtransaction
- #5937 `40f5e8d` show script verification errors in signrawtransaction result
- #5420 `1fd2d39` getutxos REST command (based on Bip64)
- #6193 `42746b0` [REST] remove json input for getutxos, limit to query max. 15 outpoints
- #6226 `5901596` json: fail read_string if string contains trailing garbage

### Configuration and command-line options
- #5636 `a353ad4` Add option `-allowselfsignedrootcertificate` to allow self signed root certs (for testing payment requests)
- #5900 `3e8a1f2` Add a consistency check `-checkblockindex` for the block chain data structures
- #5951 `7efc9cf` Make it possible to disable wallet transaction broadcast (using `-walletbroadcast=0`)
- #5911 `b6ea3bc` privacy: Stream isolation for Tor (on by default, use `-proxyrandomize=0` to disable)
- #5863 `c271304` Add autoprune functionality (`-prune=<size>`)
- #6153 `0bcf04f` Parameter interaction: disable upnp if -proxy set
- #6274 `4d9c7fe` Add option `-alerts` to opt out of alert system

### Block and transaction handling
- #5367 `dcc1304` Do all block index writes in a batch
- #5253 `203632d` Check against MANDATORY flags prior to accepting to mempool
- #5459 `4406c3e` Reject headers that build on an invalid parent
- #5481 `055f3ae` Apply AreSane() checks to the fees from the network
- #5580 `40d65eb` Preemptively catch a few potential bugs
- #5349 `f55c5e9` Implement test for merkle tree malleability in CPartialMerkleTree
- #5564 `a89b837` clarify obscure uses of EvalScript()
- #5521 `8e4578a` Reject non-final txs even in testnet/regtest
- #5707 `6af674e` Change hardcoded character constants to descriptive named constants for db keys
- #5286 `fcf646c` Change the default maximum OP_RETURN size to 80 bytes
- #5710 `175d86e` Add more information to errors in ReadBlockFromDisk
- #5948 `b36f1ce` Use GetAncestor to compute new target
- #5959 `a0bfc69` Add additional block index consistency checks
- #6058 `7e0e7f8` autoprune minor post-merge improvements
- #5159 `2cc1372` New fee estimation code
- #6102 `6fb90d8` Implement accurate UTXO cache size accounting
- #6129 `2a82298` Bug fix for clearing fCheckForPruning
- #5947 `e9af4e6` Alert if it is very likely we are getting a bad chain
- #6203 `c00ae64` Remove P2SH coinbase flag, no longer interesting
- #5985 `37b4e42` Fix removing of orphan transactions
- #6221 `6cb70ca` Prune: Support noncontiguous block files
- #6256 `fce474c` Use best header chain timestamps to detect partitioning
- #6233 `a587606` Advance pindexLastCommonBlock for blocks in chainActive

### P2P protocol and network code
- #5507 `844ace9` Prevent DOS attacks on in-flight data structures
- #5770 `32a8b6a` Sanitize command strings before logging them
- #5859 `dd4ffce` Add correct bool combiner for net signals
- #5876 `8e4fd0c` Add a NODE_GETUTXO service bit and document NODE_NETWORK
- #6028 `b9311fb` Move nLastTry from CAddress to CAddrInfo
- #5662 `5048465` Change download logic to allow calling getdata on inbound peers
- #5971 `18d2832` replace absolute sleep with conditional wait
- #5918 `7bf5d5e` Use equivalent PoW for non-main-chain requests
- #6059 `f026ab6` chainparams: use SeedSpec6's rather than CAddress's for fixed seeds
- #6080 `31c0bf1` Add jonasschnellis dns seeder
- #5976 `9f7809f` Reduce download timeouts as blocks arrive
- #6172 `b4bbad1` Ignore getheaders requests when not synced
- #5875 `304892f` Be stricter in processing unrequested blocks
- #6333 `41bbc85` Hardcoded seeds update June 2015

### Validation
- #5143 `48e1765` Implement BIP62 rule 6
- #5713 `41e6e4c` Implement BIP66

### Build system
- #5501 `c76c9d2` Add mips, mipsel and aarch64 to depends platforms
- #5334 `cf87536` libbitcoinconsensus: Add pkg-config support
- #5514 `ed11d53` Fix 'make distcheck'
- #5505 `a99ef7d` Build winshutdownmonitor.cpp on Windows only
- #5582 `e8a6639` Osx toolchain update
- #5684 `ab64022` osx: bump build sdk to 10.9
- #5695 `23ef5b7` depends: latest config.guess and config.sub
- #5509 `31dedb4` Fixes when compiling in c++11 mode
- #5819 `f8e68f7` release: use static libstdc++ and disable reduced exports by default
- #5510 `7c3fbc3` Big endian support
- #5149 `c7abfa5` Add script to verify all merge commits are signed
- #6082 `7abbb7e` qt: disable qt tests when one of the checks for the gui fails
- #6244 `0401aa2` configure: Detect (and reject) LibreSSL
- #6269 `95aca44` gitian: Use the new bitcoin-detached-sigs git repo for OSX signatures
- #6285 `ef1d506` Fix scheduler build with some boost versions.
- #6280 `25c2216` depends: fix Boost 1.55 build on GCC 5
- #6303 `b711599` gitian: add a gitian-win-signer descriptor
- #6246 `8ea6d37` Fix build on FreeBSD
- #6282 `daf956b` fix crash on shutdown when e.g. changing -txindex and abort action
- #6354 `bdf0d94` Gitian windows signing normalization

### Wallet
- #2340 `811c71d` Discourage fee sniping with nLockTime
- #5485 `d01bcc4` Enforce minRelayTxFee on wallet created tx and add a maxtxfee option
- #5508 `9a5cabf` Add RandAddSeedPerfmon to MakeNewKey
- #4805 `8204e19` Do not flush the wallet in AddToWalletIfInvolvingMe(..)
- #5319 `93b7544` Clean up wallet encryption code
- #5831 `df5c246` Subtract fee from amount
- #6076 `6c97fd1` wallet: fix boost::get usage with boost 1.58
- #5511 `23c998d` Sort pending wallet transactions before reaccepting
- #6126 `26e08a1` Change default nTxConfirmTarget to 2
- #6183 `75a4d51` Fix off-by-one error w/ nLockTime in the wallet
- #6276 `c9fd907` Fix getbalance * 0

### GUI
- #5219 `f3af0c8` New icons
- #5228 `bb3c75b` HiDPI (retina) support for splash screen
- #5258 `73cbf0a` The RPC Console should be a QWidget to make window more independent
- #5488 `851dfc7` Light blue icon color for regtest
- #5547 `a39aa74` New icon for the debug window
- #5493 `e515309` Adopt style colour for button icons
- #5557 `70477a0` On close of splashscreen interrupt verifyDB
- #5559 `83be8fd` Make the command-line-args dialog better
- #5144 `c5380a9` Elaborate on signverify message dialog warning
- #5489 `d1aa3c6` Optimize PNG files
- #5649 `e0cd2f5` Use text-color icons for system tray Send/Receive menu entries
- #5651 `848f55d` Coin Control: Use U+2248 "ALMOST EQUAL TO" rather than a simple tilde
- #5626 `ab0d798` Fix icon sizes and column width
- #5683 `c7b22aa` add new osx dmg background picture
- #5620 `7823598` Payment request expiration bug fix
- #5729 `9c4a5a5` Allow unit changes for read-only BitcoinAmountField
- #5753 `0f44672` Add bitcoin logo to about screen
- #5629 `a956586` Prevent amount overflow problem with payment requests
- #5830 `215475a` Don't save geometry for options and about/help window
- #5793 `d26f0b2` Honor current network when creating autostart link
- #5847 `f238add` Startup script for centos, with documentation
- #5915 `5bd3a92` Fix a static qt5 crash when using certain versions of libxcb
- #5898 `bb56781` Fix rpc console font size to flexible metrics
- #5467 `bc8535b` Payment request / server work - part 2
- #6161 `180c164` Remove movable option for toolbar
- #6160 `0d862c2` Overviewpage: make sure warning icons gets colored

### Tests
- #5453 `2f2d337` Add ability to run single test manually to RPC tests
- #5421 `886eb57` Test unexecuted OP_CODESEPARATOR
- #5530 `565b300` Additional rpc tests
- #5611 `37b185c` Fix spurious windows test failures after 012598880c
- #5613 `2eda47b` Fix smartfees test for change to relay policy
- #5612 `e3f5727` Fix zapwallettxes test
- #5642 `30a5b5f` Prepare paymentservertests for new unit tests
- #5784 `e3a3cd7` Fix usage of NegateSignatureS in script_tests
- #5813 `ee9f2bf` Add unit tests for next difficulty calculations
- #5855 `d7989c0` Travis: run unit tests in different orders
- #5852 `cdae53e` Reinitialize state in between individual unit tests.
- #5883 `164d7b6` tests: add a BasicTestingSetup and apply to all tests
- #5940 `446bb70` Regression test for ResendWalletTransactions
- #6052 `cf7adad` fix and enable bip32 unit test
- #6039 `734f80a` tests: Error when setgenerate is used on regtest
- #6074 `948beaf` Correct the PUSHDATA4 minimal encoding test in script_invalid.json
- #6032 `e08886d` Stop nodes after RPC tests, even with --nocleanup
- #6075 `df1609f` Add additional script edge condition tests
- #5981 `da38dc6` Python P2P testing 
- #5958 `9ef00c3` Add multisig rpc tests
- #6112 `fec5c0e` Add more script edge condition tests

### Miscellaneous
- #5457, #5506, #5952, #6047 Update libsecp256k1
- #5437 `84857e8` Add missing CAutoFile::IsNull() check in main
- #5490 `ec20fd7` Replace uint256/uint160 with opaque blobs where possible
- #5654, #5764 Adding jonasschnelli's GPG key
- #5477 `5f04d1d` OS X 10.10: LSSharedFileListItemResolve() is deprecated
- #5679 `beff11a` Get rid of DetectShutdownThread
- #5787 `9bd8c9b` Add fanquake PGP key
- #5366 `47a79bb` No longer check osx compatibility in RenameThread
- #5689 `07f4386` openssl: abstract out OPENSSL_cleanse
- #5708 `8b298ca` Add list of implemented BIPs
- #5809 `46bfbe7` Add bitcoin-cli man page
- #5839 `86eb461` keys: remove libsecp256k1 verification until it's actually supported
- #5749 `d734d87` Help messages correctly formatted (79 chars)
- #5884 `7077fe6` BUGFIX: Stack around the variable 'rv' was corrupted
- #5849 `41259ca` contrib/init/bitcoind.openrc: Compatibility with previous OpenRC init script variables
- #5950 `41113e3` Fix locale fallback and guard tests against invalid locale settings
- #5965 `7c6bfb1` Add git-subtree-check.sh script
- #6033 `1623f6e` FreeBSD, OpenBSD thread renaming
- #6064 `b46e7c2` Several changes to mruset
- #6104 `3e2559c` Show an init message while activating best chain
- #6125 `351f73e` Clean up parsing of bool command line args
- #5964 `b4c219b` Lightweight task scheduler
- #6116 `30dc3c1` [OSX] rename Bitcoin-Qt.app to Bitcoin-Core.app
- #6168 `b3024f0` contrib/linearize: Support linearization of testnet blocks
- #6098 `7708fcd` Update Windows resource files (and add one for bitcoin-tx)
- #6159 `e1412d3` Catch errors on datadir lock and pidfile delete
- #6186 `182686c` Fix two problems in CSubnet parsing
- #6174 `df992b9` doc: add translation strings policy
- #6210 `dfdb6dd` build: disable optional use of gmp in internal secp256k1 build
- #6264 `94cd705` Remove translation for -help-debug options
- #6286 `3902c15` Remove berkeley-db4 workaround in MacOSX build docs
- #6319 `3f8fcc9` doc: update mailing list address

Credits
=======

Thanks to everyone who directly contributed to this release:

- 21E14
- Adam Weiss
- Alex Morcos
- ayeowch
- azeteki
- Ben Holden-Crowther
- bikinibabe
- BitcoinPRReadingGroup
- Blake Jakopovic
- BtcDrak
- charlescharles
- Chris Arnesen
- Ciemon
- CohibAA
- Corinne Dashjr
- Cory Fields
- Cozz Lovan
- Daira Hopwood
- Daniel Kraft
- Dave Collins
- David A. Harding
- dexX7
- Earlz
- Eric Lombrozo
- Eric R. Schulz
- Everett Forth
- Flavien Charlon
- fsb4000
- Gavin Andresen
- Gregory Maxwell
- Heath
- Ivan Pustogarov
- Jacob Welsh
- Jameson Lopp
- Jason Lewicki
- Jeff Garzik
- Jonas Schnelli
- Jonathan Brown
- Jorge Timón
- joshr
- jtimon
- Julian Yap
- Luca Venturini
- Luke Dashjr
- Manuel Araoz
- MarcoFalke
- Matt Bogosian
- Matt Corallo
- Micha
- Michael Ford
- Mike Hearn
- mrbandrews
- Nicolas Benoit
- paveljanik
- Pavel Janík
- Pavel Vasin
- Peter Todd
- Philip Kaufmann
- Pieter Wuille
- pstratem
- randy-waterhouse
- rion
- Rob Van Mieghem
- Ross Nicoll
- Ruben de Vries
- sandakersmann
- Shaul Kfir
- Shawn Wilkinson
- sinetek
- Suhas Daftuar
- svost
- Thomas Zander
- Tom Harding
- UdjinM6
- Vitalii Demianets
- Wladimir J. van der Laan

And all those who contributed additional code review and/or security research:

- Sergio Demian Lerner

As well as everyone that helped translating on [Transifex](https://www.transifex.com/projects/p/bitcoin/).