PTLC Cycle Jamming

[LLFourn]

Discussion Issue for the PTLC Cycle Jamming problem

[gijswijs]

This attack is easily preventable with HTLC based payments where the lock is the same SHA256 image at each hop.

That is true. However, I am unaware of any client currently preventing payment loops. So the current state of affairs is that Cycle Jamming is already possible. Cristina Pérez-Solà wrote a paper [1] describing the attack. Maybe we should add this to the Related Research?

[1] Pérez-Solà, C., Ranchal-Pedrosa, A., Herrera-Joancomartí, J., Navarro-Arribas, G., & Garcia-Alfaro, J. (2020). LockDown: Balance Availability Attack Against Lightning Network Channels. https://doi.org/10.1007/978-3-030-51280-4_14

[gijswijs]

Preprint available here: https://eprint.iacr.org/2019/1149

[LLFourn]

Thanks @gijswijs -- this is an extremely valuable contribution to this research topic. They basically show that these cycling attacks to in practice enhance jamming attacks significantly.

See PR: #18