Published on: 2023-08-18T09:51:50+00:00
The email exchange between two individuals, Peter and the sender, begins with a disagreement over reasoning and numerical values related to probability and data loss. The sender clarifies that when computing the probability of data loss at a particular connection event, the terms used in the equation must represent the probability of data loss and the probability of being offline for several days at that connection. They point out that the joint probability of Alice losing data and displaying the behavior mentioned in the email is not simply the product of the individual probabilities. Instead, if the behavior is caused by the loss, then the joint probability is closer to the probability of loss alone.To determine whether Bob can profit from fraudulently giving Alice an incorrect backup, the sender suggests looking at the conditional probability of data loss given the information available to Bob. They introduce the concept of P(loss|behavior), which can be computed using Bayes' theorem. The sender mentions that the posterior probability of Alice losing her state will be higher if she behaves as if she has lost it.Regarding the numerical values, the sender does not dispute the probability of data loss per year but highlights that the probability of users connecting without their data becomes higher if restoring channels from seed becomes a feature. They emphasize that the frequency of users restoring their wallet from seed is more relevant than the frequency of actual data loss.The sender also brings up the point that the "behavior" mentioned in the email encompasses all the information available to Bob, not just the fact that Alice has been offline for a few days. They mention that operators of Electrum servers can infer whether Alice has been restoring from seed or not, which could be exploited by an attacker.In conclusion, the sender disagrees with the reasoning and numerical values proposed by Peter. They clarify the terms used in the equations, discuss the joint probability, introduce the concept of conditional probability, and highlight the importance of considering the behavior beyond just being offline for a few days.In this email, the sender discusses the counter-argument to a proposal related to backing up channel state. They explain why backing up channel state with the counterparty is useful and less risky than it may seem. The main reason for this is that the client can prevent fraud by checking the backup each time they connect and closing the channel immediately if the wrong backup is provided.To provide clarity, the email provides definitions for certain terms used in the argument. "V_h" is defined as the honest lifetime value of the channel to Bob, referring to the expected fees from the channel. "V_f" is the value that Bob can fraudulently obtain by giving Alice an incorrect backup. "P_d" represents the probability of data loss since the last time Alice connected to Bob.The protocol for normal operation is explained, stating that each time Alice connects to Bob, she asks for a copy of the most recent channel state backup. If the backup is incorrect, Alice force closes the channel. In the recovery phase, Alice asks for the backup again and uses it.The email then delves into the analysis of how Bob can profit from fraudulently giving Alice an incorrect backup. The condition for Bob to profit is when V_f multiplied by P_d is greater than V_h. It is noted that V_f is non-zero only when there is an increase in the channel balance from Alice's perspective. Additionally, P_d is a probability that Bob estimates based on the available information. An example scenario is provided to illustrate these points.In conclusion, the email presents a counter-argument to a proposal regarding backing up channel state. It explains the protocol for normal operation and recovery, and analyzes the conditions under which fraud could be profitable for Bob.
Updated on: 2023-08-19T01:46:54.418168+00:00