Newsletters: add #28 (2019-01-08)

Author: harding

_includes/references.md

@@ -83,10 +83,16 @@
 [newsletter #18]: {{news18}}
 {% assign news19 = "/en/newsletters/2018/10/30/" %}
 [newsletter #19]: {{news19}}
+{% assign news20 = "/en/newsletters/2018/11/06/" %}
+[newsletter #20]: {{news20}}
 {% assign news21 = "/en/newsletters/2018/11/13/" %}
 [newsletter #21]: {{news21}}
 {% assign news23 = "/en/newsletters/2018/11/27/" %}
 [newsletter #23]: {{news23}}
+{% assign news25 = "/en/newsletters/2018/12/11/" %}
+[newsletter #25]: {{news25}}
+{% assign news26 = "/en/newsletters/2018/12/18/" %}
+[newsletter #26]: {{news26}}
 
 {% comment %}
 <!--REQUIRES PERIODIC UPDATE: update rpc_version below to latest

_posts/en/newsletters/2019-01-08-newsletter.md

@@ -0,0 +1,168 @@
+---
+title: 'Bitcoin Optech Newsletter #28'
+permalink: /en/newsletters/2019/01/08/
+name: 2019-01-08-newsletter
+type: newsletter
+layout: newsletter
+lang: en
+---
+This week's newsletter announces a new maintenance release of Bitcoin
+Core, describes continued discussion about new signature hashes, and
+links to a post about possible economic barriers to LN payments crossing
+different currencies.  Descriptions of notable code changes in popular
+Bitcoin infrastructure projects are also provided.
+
+## Action items
+
+- **Upgrade to Bitcoin Core 0.17.1:** this new [minor][maintenance]
+  version released December 25th restores some previously-deprecated
+  functionality to the `listtransactions` RPC and includes bug fixes and
+  other improvements.  Consider reading the [release notes][0.17.1
+  notes] and [upgrading][0.17.1 bin].
+
+## News
+
+- **Continued sighash discussion:** as mentioned in the News section of
+  [Newsletter #25][], developers on the Bitcoin-Dev mailing list
+  discussed how signature hashes could be modified to give transactions
+  access to new capabilities.  Sighashes give spenders the ability to
+  allow their transactions to be modified in specified ways after they
+  are signed---for example, two people who open a payment channel
+  together can use a particular type of sighash to allow either one of
+  them to unilaterally attach additional transaction fees to a channel
+  close transaction.
+
+    The most recent discussion in this thread of almost 70 posts has
+    mostly involved edge cases related to new sighash flags,
+    particularly a BIP118-like `SIGHASH_NOINPUT_UNSAFE`.  As part of the
+    discussion, protocol developer Johnson Lau described an
+    [optimization for Eltoo-based payment channels][lau bip68].  Also
+    [discussed][rm codesep] is whether the `OP_CODESEPARATOR` opcode
+    should be disabled in a script update that supports MAST (e.g. via
+    Taproot).  That opcode is not in common use, but if you plan to use
+    it in future Script versions, you should comment on the thread.
+
+- **Cross-chain LN as an options contract:** pseudonymous LN
+  contributor ZmnSCPxj started a thread on the Lightning-Dev mailing
+  list pointing out that users could abuse payments that cross
+  currencies to create almost free [short-term options contracts][] by
+  delaying payment settlement.  A [previous thread][cjp risk] by Corné
+  Plooy in May 2018 described the same thing.
+  
+    For example, Mallory learns that Bob is willing to route payments
+    from Bitcoin to Litecoin, so she sends a payment from one of her
+    Bitcoin nodes through Bob to one of her Litecoin nodes.  If this
+    were a normal payment, she'd settle it immediately by releasing the
+    preimage for the payment's hashlock---but instead her node delays
+    for 24 hours waiting for the exchange rate to change.  If the
+    exchange rate increases in Litecoin's favor, Mallory settles the
+    payment and receives litecoin today at yesterday's exchange rate.
+    If the exchange rate stays the same or increases in Bitcoin's favor,
+    Mallory causes the payment to fail and gets her bitcoin back.  Since
+    no fees are charged for failed payments, Mallory received an
+    opportunity to temporarily lock-in the price of Litecoin for nothing
+    but the cost of owning the bitcoins Mallory would've traded.
+
+    There currently aren't any known cross-currency LN nodes, but the
+    availability of this trick means that future such nodes could be
+    abused for speculation rather than payment routing.  If this turns
+    out to be a real problem and if an acceptable solution isn't found,
+    it may be the case that payment channel networks for different
+    currencies will be isolated from each other.
+
+## Notable code changes
+
+*Notable code changes this week in [Bitcoin Core][core commits],
+[LND][lnd commits], [C-lightning][cl commits], and [libsecp256k1][secp
+commits].*
+
+- [Bitcoin Core #14565][] significantly improves the error handling for
+  the `importmulti` RPC and will return a `warnings` field for each
+  attempted import with an array of strings describing any problems with
+  the that import (but only if there were any problems).
+
+- [Bitcoin Core #14811][] updates the [getblocktemplate][rpc
+  getblocktemplate] RPC to require that the segwit flag be passed.  This
+  helps prevent miners from accidentally not using segwit, which reduces
+  their fee income.  See [Newsletter #20][] for a recent instance where
+  this may have happened to a large mining pool.
+
+- [Bitcoin Core #14336][] changes the system call (syscall) Bitcoin Core
+  uses to handle network connections and other resources on platforms
+  that support an alternative syscall (only Linux for now).  On a
+  Debian GNU/Linux x86_64 system tested by Optech, this increased the
+  maximum allowed number of connections from 865 to 9,999.  Please note,
+  developers strongly advise against increasing the maximum number of
+  connections unless you have a special need for more connections.  For
+  each peer you have after your first peer, you increase the amount of
+  bandwidth overhead used by your node and by all of your peers.  The
+  default minimum of 8 and maximum of 125 peers were chosen to provide
+  enough connections to ensure robust relaying but also to not create so
+  much bandwidth overhead that the network would be excessively
+  wasteful.  As relay improvements are implemented (see the News section
+  of [Newsletter #26][]), Bitcoin Core developers may adjust these
+  defaults.
+
+- [C-Lightning #2172][] allows `lightningd` to be shutdown normally even
+  if it's operating as the primary process (PID 1), which can be useful
+  in Docker containers.
+
+- [C-Lightning #2188][] adds notification subscription handlers that can
+  be used by plugins, with initial support for notifications that the
+  node has connected to a new peer or disconnected from an existing
+  peer.  The [plugin documentation][cl plugin event] and [sample
+  plugin][cl helloworld.py] have been updated for these handlers.
+
+- [LND #2374][] increases the maximum size of the gRPC messages the
+  `lncli` tool will accept from 4 MB to 50 MB.  This fixes a problem
+  some nodes were encountering where the `describegraph` RPC was failing
+  due to the network having grown so large that messages exceeded this
+  limit.  Developers using gRPC directly will need to increase their
+  client-side maximum message size setting---descriptions of how to do
+  this have already been added as comments to the PR for python and nodejs.
+  Ultimately it's expected that the network will grow large enough to
+  exceed even this new maximum, so developers are planning to revamp the
+  relevant RPCs to handle this situation.
+
+- [LND #2354][] adds a new `invoicestate` field and deprecates the former
+  `settled` field in RPCs that get information about invoices.  The
+  settled field was boolean but the new state field can support multiple
+  values.  Currently this is just "open" or "settled", but additional
+  future states are planned.
+
+{% include references.md %}
+{% include linkers/issues.md issues="14565,14811,14336,2172,2188,2374,2354" %}
+{% include linkers/github-log.md
+  refname="core commits"
+  repo="bitcoin/bitcoin"
+  start="34241716852df6ea6a3543822f3bf6f886519d4b"
+  end="fe5a70b9fefa0548f497a749746f53f3d7fd0ebb"
+%}
+{% include linkers/github-log.md
+  refname="lnd commits"
+  repo="lightningnetwork/lnd"
+  start="0fafd5e2fd824f38ec6a03a56488de9c0798f34f"
+  end="3c950e8f0dc103feeffd9c42c9683e1164b4e8d8"
+%}
+{% include linkers/github-log.md
+  refname="cl commits"
+  repo="ElementsProject/lightning"
+  start="2c53572798f78ce2a66aced0627b7b3f2adb0514"
+  end="6f027a24a04912859f44c314bf00e9d3fcb27500"
+%}
+{% include linkers/github-log.md
+  refname="secp commits"
+  repo="bitcoin-core/secp256k1"
+  start="e34ceb333b1c0e6f4115ecbb80c632ac1042fa49"
+  end="e34ceb333b1c0e6f4115ecbb80c632ac1042fa49"
+%}
+
+[0.17.1 bin]: https://bitcoincore.org/bin/bitcoin-core-0.17.1/
+[0.17.1 notes]: https://bitcoincore.org/en/releases/0.17.1/
+[maintenance]: https://bitcoincore.org/en/lifecycle/#maintenance-releases
+[lau bip68]: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-December/016574.html
+[rm codesep]: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-December/016581.html
+[short-term options contracts]: https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-December/001752.html
+[cjp risk]: https://lists.linuxfoundation.org/pipermail/lightning-dev/2018-May/001292.html
+[cl plugin event]: https://github.com/ElementsProject/lightning/blob/master/doc/plugins.md#event-notifications
+[cl helloworld.py]: https://github.com/ElementsProject/lightning/blob/master/contrib/plugins/helloworld.py