Zero-fee commitments for mobile wallets

It debates the merits of allowing LSPs to set transaction fees due to their continuous online presence and thus more accurate assessment of fee rates compared to mobile wallet users. This is seen as a way to simplify operations and reduce the risk of force-closes, although it acknowledges potential issues during sudden spikes in fee rates which LSPs might not adjust to promptly. To counteract the limitations of predicting fee rate changes and the imperfect view of the mempool/fee rate from mobile wallets, the proposal suggests opting for a longer min_final_expiry_delta, extending the confirmation window during volatile fee periods. The importance of enhancing security protocols to deter dishonest behavior by LSPs is emphasized, acknowledging that while no solution guarantees 100% security, the objective is to make cheating as difficult as possible without adding undue complexity.

Further, the conversation explores the technical nuances of blockchain transactions, highlighting the innovative use of SIGHASH_SINGLE | SIGHASH_ANYONECANPAY. This allows for the addition of inputs to cover transaction fees, presenting a method for optimizing transaction costs notably in scenarios where the default 0-fee HTLC transaction applies. It proposes an alternative signing method for HTLC-success transactions, suggesting a switch to the SIGHASH_ALL flag to mitigate potential exploits by users manipulating transactions for excess mining fees. Additionally, the dialogue elucidates on the enhancement of the second pre-signed HTLC-success transaction through the integration of spending the shared anchor, underscoring the significance of detailed documentation for understanding complex technical processes.

The intricacies of handling pending incoming HTLC transactions are dissected, illustrating the mechanism involving two versions of the HTLC-success transaction to accommodate different fee strategies. This includes a default version without transaction fees and another with a high feerate encapsulated within a custom TLV of commitment_signed. The discussions raise concerns about zero-fee P2A transactions under the ephemeral dust policy, querying whether an additional UTXO is needed to effectively spend the P2A output, thereby aligning with network relay standards.

The vulnerability of the Lightning Network to exploitation via pre-signed HTLC transactions by malicious wallets is analyzed. It describes a scenario where a wallet could shift the burden of on-chain fees to its peer through strategic broadcasting of revoked commitment transactions. Despite this, various mitigating factors such as initial channel creation fees, routing fees, and the ability to cap feerates are identified, suggesting that the overall risk remains manageable.

The economic dynamics of HTLC transactions are reevaluated, revealing that the owner of the HTLC transaction, typically a mobile wallet user, bears the responsibility for fees. This system, while efficient, opens avenues for exploitation but also incorporates mechanisms to ensure financial equity within the network. The proposal introduces an approach for peers to sign two versions of HTLC transactions, aiming to improve transaction efficiency and safety without imposing additional costs on the peer.

Innovation continues with the development towards incorporating zero-fee commitments to enhance mobile wallet functionality within the cryptocurrency domain. This focuses on simplifying operational requirements against adversarial conditions and increasing mobile wallet adoption for cryptocurrency transactions. Feedback is solicited to refine these enhancements, with the goal of formalizing them in a bLIP upon reaching consensus.