[Question]Users have to be online once a half week? about plasma-cash HOT 3 CLOSED

TLDR You need to allow multiple challenges per exit, or loss of funds can occur. Extending the exit period is not feasible because of the griefing vector that I described above. An alternative to splitting the challenge period, is to simply not allow an exit to be finalized if it has pending challenges. This is done in https://github.com/counterfactual/plasma-cash however it does not work with security bonds.

Long version: Your suggestion was the first approach I had. However, this means that a malicious challenger can infinitely extend a coin's exit (at the cost of 1 bond per exit period extension).

Attack:
A exits coin
M challenges exit at seconds before 7 days (needs to put up a security bond)
Challenge period gets extended by 3 days (example)
A responds to the challenge, exit can be finalized after the 3 days pass. M also loses the security bond.
M challenges exit at seconds before 3 days.
...(repeat)

The naive solution to the above is to allow the exit to be challenge only once. This however is also broken, since (by collaborating with the operator), a user can try to exit a coin with an invalid history, challenge their own exit, and then respond to their own exit, making the coin no longer challenge-able.

from plasma-cash.

We split the challenge period for challenges with invalid history to avoid an attack where an interactive challenge is made right before the challenge period is over and there is not enough time to respond to it. The full 7 days can be used for non-interactive challenges. The 7 days is just a security parameter and you can adjust it to be however much you want.

from plasma-cash.

Thank you for your replying! I understood.

This is just a question.
Extending "respondChallenge period" when challengeBefore occurred is not good implementation?

from plasma-cash.