Merge revault#106: Larger feerate for the Emergency transaction

38b5fbf transactions: increase Emergency feerate to 300sat/vb (Antoine Poinsot)
67058a7 transactions: fix an incorrect feerate (Antoine Poinsot)
26f51a2 messages: move transactions pre-signed feerate specs to transactions.md (Antoine Poinsot)

Pull request description:

  Fixes revault#86

ACKs for top commit:
  danielabrozzoni:
    concept ACK 38b5fbf
  JSwambo:
    Ack 38b5fbf

Tree-SHA512: 72102756e2fe7b6c59b575486caa0fc9cb3671d205e92d3de9876b1a785d2e82f2faf5bfadaca29c2fc5230953b535d7d5846c58bfd7bfe74e69b9dc65698492

messages.md

@@ -176,17 +176,6 @@ loss of funds.
 Acting as a cache in place of -example given- a p2p network, the information stored on the
 coordinator is transient.
 
-All [revaulting transactions][revaulting_txs] (the cancel tx and both emergency txs) are signed
-paying a fixed `22 sat/WU` feerate and using the `ALL | ANYONECANPAY` signature hash flag. This
-is in order to reduce the funds burden on *each* of the watchtowers.
-
-The [unvault transaction][unvault_tx] is signed using a fixed `6 sat/WU` feerate. This is
-a completely arbitrary value that was chosen to avoid blocking operations too early in case of
-a huge load of transactions on the network and an increase of the mempools minimum feerate.  
-This transaction's fees can be bumped if not competitive (using the CPFP output) but
-it will likely not be relayed if the mempools minimum feerate goes above `84 000 sat/kw`
-until the Bitcoin network deploys [package relay][package_relay].
-
 
 ### Rough flow
 
@@ -476,4 +465,3 @@ manager         cosig_server
 
 [revaulting_txs]: transactions.md#cancel_tx
 [unvault_tx]: transactions.md#unvault_tx
-[package_relay]: https://github.com/bitcoin/bitcoin/issues/14895

transactions.md

@@ -43,6 +43,14 @@ The transaction which spends the [`deposit_tx`](#deposit_tx) deposit output, and
 unvault output spendable by the `N` stakeholders or the managers (along with the cosigning
 servers) after `X` blocks.
 
+The Unvault transaction is signed using a fixed `6 sat/WU` feerate. This is a
+completely arbitrary value that was chosen to avoid blocking operations too early
+in case of a huge load of transactions on the network and an increase of the
+network mempools minimum feerate.  
+This transaction's fees can be bumped if not competitive (using the CPFP output) but
+it will likely not be relayed if the network mempools minimum feerate goes above
+`24 sat/vb` until [package relay][package_relay] is deployed on the Bitcoin network.
+
 - version: 2
 - locktime: 0
 
@@ -115,6 +123,12 @@ The CPFP output value is adjusted depending on the actual transaction size.
 The transaction which spends the [`unvault_tx`](#unvault_tx) `output[0]` using the N-of-N path and 
 pays back to a deposit output (it is therefore another vault deposit transaction).
 
+The Cancel transaction is signed using the `ALL | ANYONECANPAY` signature hash flag, to
+allow watchtowers (or anyone else) to attach fee-bumping inputs.
+
+The Cancel transaction is signed at a fixed `22 sat/WU` feerate. This is in order to
+reduce the funds burden on *each* of the watchtowers.
+
 - version: 2
 - locktime: 0
 
@@ -138,11 +152,16 @@ pays back to a deposit output (it is therefore another vault deposit transaction
 
 ## emergency_txs
 
-Emergency transactions are used as deterrents against threats targetting stakeholders' 
-funds. They lock coins to what we call an EDV (Emergency Deep Vault): a script chosen 
-by the participants and kept obfuscated by the properties of P2WSH, as the emergency 
+Emergency transactions are used as deterrents against threats targeting stakeholders'
+funds. They lock coins to what we call an EDV (Emergency Deep Vault): a script chosen
+by the participants and kept obfuscated by the properties of P2WSH, as the emergency
 transactions are never meant to be used.
 
+Both Emergency transactions are signed at a fixed `75 sat/WU` feerate.
+
+Both Emergency transaction are signed using the `ALL | ANYONECANPAY` signature hash flag,
+to allow watchtowers (or anyone else) to attach fee-bumping inputs.
+
 The Emergency `scriptPubKey` is not known to the managers.
 
 
@@ -218,3 +237,6 @@ Bypass tx spends the [`deposit_tx`](#deposit_tx) and pays to arbitrary addresses
 #### OUT
 
 Unspecified
+
+
+[package_relay]: https://github.com/bitcoin/bitcoin/issues/14895