Replace by fee (RBF) or fee replacement, is a method that allows you to unlock bitcoin (BTC) shipments stuck in the mempool. Now, a programmer has proposed moving away from the optional use of RBF and making it a standard in all transactions within the main Bitcoin network.
This model, according to the Bitcoin portal Optech in its newsletter of June 23, was not adopted as a standard in all transactions due to the problems arising from the merchants accepting payments with 0 network confirmations.
Five years after the implementation of the RBF in the BIP125, and views that very few merchants accept transactions with 0 confirmations, the programmer Antoine Raid, published in the mailing list Bitcoin-Dev a proposal to change the source code of Bitcoin Core, establishing that all transactions within the network use RBF.
This would mean that regardless of the wallet used, users will be able to create RBF transactions to unlock stuck payments in the Bitcoin mempool. It should be noted that, if the standard is implemented, it will not mean any significant change at the time of sending and receiving payments.
As the Raid itself describes, standardizing RBF would imply an improvement in privacy, given that there would be no distinction between transactions with or without RBF.
The problem of double spending in the RBF
In the newsletter, Raid answers questions about whether RBF transactions can be a window for double-spend attacks (make two payments with the same unit of cryptocurrency). In this sense, it establishes a security model of double-expenditure monitoring by the receiver, which it would allow tracking of incoming RBF transactions.
As an additional measure of protection, Raid also mentions CPFD (children pay for parents) transactions. This is a model similar to RBF transactions, in which, if a double spend intent is detected using RBF, before the original transaction receives 1 network confirmation, the receiver generates a CPFD transaction, with a fee much higher than that generated by the attacker. In this way BTC theft is prevented.
Adoption challenges
Antoine Raid comments that making RBF a standard for all blockchain transactions would be, at first, only for Bitcoin’s core network.
The Lightning second layer network, for example, although it is already quite established, it still has very new developments as dual funding channels or deferred funding, an implementation that allows users to open paid channels by sharing the cost of opening between both ends of the channel (user and network node).
Being at an early stage of development, Raid says that “a maturity phase” must first be achieved to measure and mitigate the risks that would come with adopting RBF transactions by default in Bitcoin’s layer two solutions.
In this regard, last year, a vulnerability involving Bitcoin’s Lightning network and RBF transactions was unveiled. As CriptoNoticias reported, this flaw allowed attackers to steal BTC from anchor channels by swapping the compromise transaction for another, via an RBF transaction.