#### Removal of reject network messages from Bitcoin Core (BIP61)
The command line option to enable BIP61 (`-enablebip61`) has been removed.
This feature has been disabled by default since Bitcoin Core version 0.18.0.
Nodes on the network can not generally be trusted to send valid ("reject")
messages, so this should only ever be used when connected to a trusted node.
Please use the recommended alternatives if you rely on this deprecated feature:
* Testing or debugging of implementations of the Bitcoin P2P network protocol
should be done by inspecting the log messages that are produced by a recent
version of Bitcoin Core. Bitcoin Core logs debug messages
(`-debug=<category>`) to a stream (`-printtoconsole`) or to a file
(`-debuglogfile=<debug.log>`).
* Testing the validity of a block can be achieved by specific RPCs:
-`submitblock`
-`getblocktemplate` with `'mode'` set to `'proposal'` for blocks with
potentially invalid POW
* Testing the validity of a transaction can be achieved by specific RPCs:
-`sendrawtransaction`
-`testmempoolaccept`
* Wallets should not use the absence of "reject" messages to indicate a
transaction has propagated the network, nor should wallets use "reject"
messages to set transaction fees. Wallets should rather use fee estimation
to determine transaction fees and set replace-by-fee if desired. Thus, they
could wait until the transaction has confirmed (taking into account the fee
target they set (compare the RPC `estimatesmartfee`)) or listen for the
transaction announcement by other network peers to check for propagation.
The removal of BIP61 REJECT message support also has the following minor RPC
and logging implications:
*`testmempoolaccept` and `sendrawtransaction` no longer return the P2P REJECT
code when a transaction is not accepted to the mempool. They still return the
verbal reject reason.
* Log messages that previously reported the REJECT code when a transaction was
not accepted to the mempool now no longer report the REJECT code. The reason
for rejection is still reported.
Updated RPCs
------------
-`testmempoolaccept` and `sendrawtransaction` no longer return the P2P REJECT
code when a transaction is not accepted to the mempool. See the Section
_Removal of reject network messages from Bitcoin Core (BIP61)_ for details on
the removal of BIP61 REJECT message support.
- A new descriptor type `sortedmulti(...)` has been added to support multisig scripts where the public keys are sorted lexicographically in the resulting script.
-`walletprocesspsbt` and `walletcreatefundedpsbt` now include BIP 32 derivation paths by default for public keys if we know them. This can be disabled by setting `bip32derivs` to `false`.
