This release makes some core features mandatory, includes a few important bug fixes and several performance improvements.
It is fully compatible with 0.5.1 (and all previous versions of eclair).

Major changes

Mandatory payment secrets

This release makes two important features mandatory:

• var_onion_optin (added to the spec in July 2019)
• payment_secret (added to the spec in December 2019)

These features have been widely deployed and protect against privacy attacks and stealing payments to 0-value invoices (as described here).
You won't be able to connect to nodes that don't support these features nor pay invoices that don't include a payment_secret.

Improved detection of stale blocks

Eclair uses ZMQ to receive blocks and transactions from your bitcoin node.
While ZMQ is usually very reliable, we discovered that its pub/sub model has some limitations.
If a subscriber encounters network failures, it will silently disconnect without notifying the publisher.
This never happens when your bitcoin node is on the same machine as eclair, but may happen when bitcoin is running on a remote machine and a VPN is used between the two machines.
Eclair now sets a TCP keep-alive on the ZMQ socket to work around this limitation and quickly reconnect.

The blockchain watchdogs have also been improved to run at fixed intervals if no blocks are received.
They will poll secondary blockchain sources (bitcoinheaders.net, blockstream.info, mempool.space and blockcypher.com) to detect that your eclair node is missing blocks.

Electrum support removed

This release removes support for using Electrum instead of Bitcoin Core for your bitcoin wallet.
Electrum support was necessary for mobile wallets, but wasn't recommended for server deployments.
Wallets are migrating to our Kotlin lightning stack, so eclair can now target exclusively server deployments.

Eclair depends on many low-level bitcoind RPCs for fee bumping which aren't available yet in Electrum.

Improved Postgres support

We previously introduced beta support for using PostgreSQL as database backend in eclair v0.4.1.
We've fixed some bugs since then and improved the integration, but please note that PostgreSQL support is still in beta.
We're actively working on finalizing this integration and making PostgreSQL production-ready in a future release.

Support for future segwit versions

This release adds support for option_shutdown_anysegwit (spec PR available here).
Current segwit bitcoin addresses (P2WPKH and P2WSH) only use segwit version 0, but this change lets nodes use bitcoin addresses with other version numbers (taproot will use version 1).

API changes

This release updates a few APIs:

• Features are now displayed as a map (feature name -> support) in API responses (#1715)
• Channel internal state tracking force-close scenarios has been enriched (#1728)
• A --blocking=<bool> option has been added to the payinvoice API (#1751)

We've also updated our internal API DSL, which paves the way for more plugin integration in a future release.
Head over to our API documentation for more details.

Miscellaneous improvements and bug fixes

• Eclair now defaults to Bech32 addresses (#1717)
• Anchor output commitment feerate is now configurable (#1718)
• All outputs of revoked anchor output commitments are claimed (there is a subtle edge case, see #1738)
• Internal codec packages and database versions have been reworked to improve future backwards-compatibility
• Several improvements have been made to our path-finding algorithms, improving tail latency
• A bug affecting reconnections to peers has been fixed (#1760)
• A bug affecting transaction outputs ordering (which can lead to channel force-close) has been fixed (#1806)

Verifying signatures

You will need gpg and our release signing key 7A73FE77DE2C4027. Note that you can get it:

• from our website: https://acinq.co/pgp/drouinf.asc
• from github user @sstone, a committer on eclair: https://api.github.com/users/sstone/gpg_keys

To import our signing key:

$ gpg --import drouinf.asc

To verify the release file checksums and signatures:

$ gpg -d SHA256SUMS.asc > SHA256SUMS.stripped
$ sha256sum -c SHA256SUMS.stripped

Building

Eclair builds are deterministic. To reproduce our builds, please use the following environment (*):

• Ubuntu 20.04
• AdoptOpenJDK 11.0.6
• Maven 3.8.1

Use the following command to generate the eclair-node package:

mvn clean install -DskipTests

That should generate eclair-node/target/eclair-node-0.6.0-XXXXXXX-bin.zip with sha256 checksums that match the one we provide and sign in SHA256SUMS.asc

(*) You may be able to build the exact same artefacts with other operating systems or versions of JDK 11, we have not tried everything.

Upgrading

This release is fully compatible with eclair v0.5.1. You don't need to close your channels, just stop eclair, upgrade and restart.

Changelog

• 163700a Set version to 0.5.2-SNAPSHOT (#1714)
• 844829a Features should be a Map (#1715)
• afa378f Fix Bolt 3 spec change that broke our test suite (#1719)
• c4c0248 Use bech32 addresses by default (#1717)
• 92e53dc Configurable anchor output max commitment feerate (#1718)
• ea8f940 Fix potential race condition in node-relay (#1716)
• 9ff2f83 Refactor and simplify API dsl (#1690)
• 6364ae3 Reject trampoline payments with expired outgoing cltv (#1727)
• 2772138 Better handling of TemporaryChannelFailure (#1726)
• ded5ce0 Add metadata to local_channels table (#1724)
• 8dc64db Fix API regression (#1729)
• 4bc2dec Reorganize internal codecs (master) (#1732)
• 6d28cbc Rework XxxCommitPublished types (#1728)
• 6e72785 fixup! Rework XxxCommitPublished types (#1728) (#1735)
• 7819fae Move protocol codecs to their own package (#1736)
• 3d3766e Clarify some comments and add tests (#1734)
• f39718a Add high-level architecture diagrams (#1733)
• f202587 Clarify commit tx fee anchor cost (#1721)
• c37eb1a Handle aggregated anchor outputs htlc txs (#1738)
• e5429eb Avoid visiting vertices multiple times in Dijkstra's algorithm (#1745)
• c6a76af Introduce actor factories (#1744)
• 75cb777 Prevent loops and improve shortest paths perf (#1747)
• 936f36b Refactor Postgres code (#1743)
• ac2b784 Fix flaky relay-htlc-add test (#1752)
• 5729b28 Add blocking option to payinvoice API (#1751)
• 89d2489 Remove Electrum support (#1750)
• b25e552 Remove Docker test dependency (#1753)
• 1321761 Make signing payment requests faster (#1754)
• 5f68bf9 Database nits (#1755)
• 1e2abae Index database metrics by backend (#1758)
• 6518bb4 Posgres: fix concurrency in channels db (#1762)
• 3da0b80 Add a list of community plugins (#1763)
• 48c0c4c Extract tx publishing from watchers (#1749)
• 357f7f9 Catch all connection failures and reconnect (#1760)
• 205653d Make db errors fatal in channels (#1764)
• ccae92d (Minor) Minimize conflicts with feature branches (#1765)
• eb834e2 Do not explicitly provide address for ServerSocket in tests (#1766)
• d0e79fa Add shorter CI timeout (#1769)
• 15ddc17 Add trampoline info to auditDB (#1767)
• 32a86a4 Ignore tests with ServerSocket (#1776)
• 33d52b6 More database nits (#1773)
• e092677 Rework the db version management (#1775)
• 4a1dfd2 Reenable ServerSocket tests (#1777)
• e14c40d Use proper data type for timestamps in Postgres (#1778)
• 62dd393 Use bouncycastle instead of spongycastle (#1772)
• 3669428 Don't log ClosingType object (#1781)
• 223a14c Remove bintray (#1785)
• 9e4042f Migrate ZmqWatcher to akka-typed (#1759)
• 90fbcd3 Index trampoline payments by hash and secret (#1770)
• 3079cb4 Remove unused class (#1792)
• a8d4e07 Use less strict isolation level for channel meta (#1790)
• 55b50ec ZMQ actors should subscribe to a single topic (#1793)
• c641549 Fix computation of path weight (#1794)
• 340fd29 Update default path-finding weight ratios (#1796)
• 55a629f Update instructions for downloading Tor Bundle (#1784)
• 898c17b Remove ConnectionControlPlugin trait (#1797)
• 0805d51 Do not retry sending if payment gets confirmed on chain (#1799)
• ec276f8 Use satoshi for htlc ordering (#1806)
• 9c3ee59 Check blockchain watchdogs regularly (#1808)
• 9141998 Make payment_secret mandatory (#1810)
• 1fbede7 Add TCP keep-alive on ZMQ socket (#1807)
• 5a92f84 Add support for option_shutdown_anysegwit (#1801)
• e2b3b47 Update Tor doc for Windows (#1811)
• f746ade Set version to 0.6.0 (#1812)

Special thanks to @tompro who reworked our internal API DSL.