Bitcoin Core 0.11

Bitcoin Core 0.11

Developers	Bitcoin Core developers
Initial release	July 7, 2015
Written in	C++
OS	Windows, macOS, Linux
License	MIT License
Website	bitcoincore.org

Bitcoin Core 0.11 is a version of the Bitcoin Core software. It was released on July 7, 2015 for the Windows, MacOS, and Linux platforms. It is notable for increasing the default minimum relay fee (minrelayfee) to 1000 satoshi per kilobyte.

It introduced significant improvements, including up to 30% faster initial block download through optimized block index and reduced disk I/O, built-in Tor support for enhanced privacy (-torcontrol, -onion options), and new RPC commands like getrawtransaction with blockhash. The -txindex flag enables full transaction indexing, while wallet export/import and Qt GUI issues (e.g., coin control, transaction list rendering) were improved. Network enhancements include better peer management, dynamic DNS seed updates, and stronger DoS protection. Various consensus bugs were fixed for stability.

Background

In early 2015, Bitcoin's network faced significant strain from transaction flooding, exemplified by the Coinwallet.eu Spam attack, the first of four dust storms that summer. Launched between block heights 364133 and 372767 (July 6 to September 2, 2015), this attack consisted of 169,761 transactions with 99 outputs of 0.0001 BTC each, consuming 356 vMB of block space, 73 BTC in fees, and creating 95 BTC in dust outputs—publicly claimed by the entity CoinWallet.eu. Unlike prior dust events, it directly impacted users by filling the mempool, spiking block space costs from $0.40 to $0.60 per kilobyte and extending low-fee confirmation waits from 1 to 87 blocks, while causing abnormal UTXO set growth—particularly in tiny-value outputs. This wave, analyzed in a 2017 Breaking Bitcoin presentation, set the stage for broader scalability debates as transaction volumes surged with Bitcoin's adoption.

A few weeks later, the RIP Bitcoin Attack intensified the crisis from July 7 to 17, 2015, with 385,256 spam transactions (23.41% of 1,645,667 total) featuring 102 dust outputs of 0.0001 BTC each, traced to 10 automated wallets via cluster analysis in a subsequent research paper. This flood, dubbed after an anonymous "RIP Bitcoin" IRC message, cost attackers at least $49,000 USD but raised average fees by 51% (45 to 68 sat/byte) and delays by 7x (0.33 to 2.67 hours) for legitimate transactions. Bitcoin Core developers responded swiftly by setting a default setting of 1,000 satoshi per kilobyte minimum relay fee in version 0.11.0 as a mitigation.