Segwit | Replace-by-Fee

Segwit Addresses

What are segwit addresses? Transactions that spend bitcoins secured by segregated witness (segwit) use less block weight than equivalent non-segwit (legacy) transactions, allowing segwit transactions to pay less total fee to achieve the same feerate as legacy transactions.

Tested: version 3.5.1 on iOS

Tested on: 2020-01-24

Receive support

• Allows receiving to P2SH-wrapped segwit
  Allows the generation of P2SH-wrapped (either P2WPKH or P2WSH) segwit receiving addresses.

• Allows receiving to bech32 segwit addresses
  Allows the generation of bech32 native (either P2WPKH or P2WSH) segwit receiving addresses.

• Default receiving address is bech32 P2WPKH
  This service generates bech32 P2WPKH segwit receiving addresses by default.

Send support

• Allows sending to bech32 P2WPKH addresses
  Allows sending to bech32 P2WPKH native segwit addresses.

• Allows sending to bech32 P2WSH addresses
  Allows sending to bech32 P2WSH native segwit addresses.

• Creates bech32 change addresses
  When sending, generates bech32 (either P2WPKH or P2WSH) segwit change addresses.

Usability

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Cash App uses bech32 p2wpkh native segwit addresses for receiving.

Cash App allows sending to either wrapped or native segwit addresses.

Replace-by-Fee (RBF)

What is Replace-by-Fee (RBF)? An unconfirmed transaction can be replaced by another version of the same transaction that spends the same inputs. Most full nodes support this if the earlier transaction enables BIP125 signaling and the replacement transaction increases the amount of fee paid. In terms of block chain space used, this is the most efficient form of fee bumping.

Tested: version 3.5.1 on iOS

Tested on: 2020-01-24

Receiving support

• Notification does not note RBF
  Notification of incoming transaction does not note that the transaction signals RBF.

• Received transaction not labeled replaceable in list
  Does not visually indicate that an incoming transaction has signaled RBF.

• Received transaction not labeled replaceable in transaction details
  Does not visually indicate that a received transaction has signaled RBF when viewing the transaction details.

• No unconfirmed transactions
  Neither the original nor replacement transactions are shown in the transaction list. Unconfirmed transactions are probably not supported.

Sending support

• Does not signal BIP125 replacability when sending transactions
  Does not allow sending of BIP125 opt-in-RBF transactions in the interface.

• Not tested: Does transaction list show whether sent transactions signal RBF?
  We were not able to test this because sending a BIP125 signaling transaction is not supported.

• Not tested: Does transaction details page show whether received transaction signals RBF?
  We were not able to test this because sending a BIP125 signaling transaction is not supported.

• Not tested: Are replacement and original sent transactions displayed?
  We were not able to test this because sending a BIP125 signaling transaction is not supported.

Usability

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Sending RBF Transaction - Default send transaction screen.

Sending RBF Transaction - Send transaction confirmation screen. Transaction sent without RBF signaled.

Bumping RBF Transaction - Transaction details screen. Transaction not sent with RBF so no bumping possible.

Bumping RBF Transaction - Transaction list screen. Transaction not sent with RBF so no bumping possible.

Receiving RBF Transaction - Transaction email notification. No RBF notice (email occurred after confirmation).

Receiving RBF Transaction - Transaction list screen. Unconfirmed incoming transactions are shown as ‘Pending’ unless the transaction signals RBF in which case it only appears in the ‘Completed’ list after confirmation.

Receiving RBF Transaction - Transaction details. No RBF notice.