From ZmnSCPxj at protonmail.com  Fri May 18 23:38:26 2018
From: ZmnSCPxj at protonmail.com (ZmnSCPxj)
Date: Fri, 18 May 2018 19:38:26 -0400
Subject: [Lightning-dev] Mitigations for loop attacks
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Good morning Rusty,


> Also, you talked about reputation_loss_rate as being a private per-node
> 
> thing, and being an explicit thing in the HTLC. I'm ignoring the
> 
> former, and assuming the latter.

Reputation (the score) is a private per-node thing, while the `reputation_loss_rate` is explicit in the HTLC.

I am uncertain how that changes your analysis, though.  In a line network like you showed, the reputation "bins" are Node1->Node2 and Node2->Node1 and so on.  It may be more useful to think of the reputation bins as assigned to half-chans than to nodes.

So the initial Mallory3->Node18->Mallory2 gives high reputation to half-chans Node18->Mallory3 and Node18->Mallory2, then sacrifices the Node18->Mallory3 reputation to destroy the NodeN -> NodeN+1 and NodeN+1->NodeN reputations.

Along that line, reputation lost is higher as N increases. Graphing reputation lost along that line, we form a triangle, and the area of the triangle is the total reputation destroyed.  Only the length of one edge of the triangle is what is lost by the Node18->Mallory3 reputation score.  So yes, it seems you are correct here.

Regards,
ZmnSCPxj