Fee-Based Spam Prevention For Lightning

Understanding the intricacies of channel jamming within the context of the Lightning Network reveals both the vulnerabilities and potential solutions to mitigate such issues. A scenario where an attacker targets a channel with 120 slots, intending to jam it for two weeks, demonstrates the low cost of executing such an attack. Specifically, for payments of 10k sats, the Hold Fee would amount to approximately 8k sats, and remarkably, this figure drops to just 0.8 sats for 1-sat payments. This calculation is based on the assumption that the maximum number of accepted HTLCs (Hashed Time-Locked Contracts) is set to 483 as per BOLT 02 specifications, suggesting that for a full-scale attack, the costs could quadruple to 32k sats for larger payments and 3.2 sats for minimal ones.

The analysis extends beyond the Hold Fee to include other financial charges like the Upfront Fee and Success Fee, which collectively aim to cover various operational and risk-related costs associated with routing payments through the network. The Upfront Fee, in particular, compensates for computation, communication, and the allocation of channel resources to the payment, among other factors. It's highlighted that an appropriately high per-slot component of the Upfront Fee could deter slot jamming by making the attack prohibitively expensive, effectively protecting the network from such exploits.

Further discussion introduces innovative approaches to reducing the vulnerability of channels to jamming attacks. One proposed method involves optimizing the channel's funds by creating two separate channels: one with a smaller capital reserve specifically for minor transactions. This bifurcation ensures that even if each channel imposes a Hold Fee based on the higher of the payment value or the channel's capital divided by 483, the fees for small payments remain low, thereby minimizing the incentive for attackers to jam the channel with negligible transactions.

Another noteworthy strategy is the adoption of the OPR protocol (OPR Protocol), which presents a robust solution by eliminating delays in payment processing and eradicating on-chain charges for resolving payments. This protocol stands out as a promising alternative for efficiently routing small payments without the threat of channel jamming, marking a significant advancement in securing the Lightning Network's infrastructure against malicious activities.