Anthony Towns [ARCHIVE] on Nostr: 📅 Original date posted:2015-10-16 📝 Original message: On Fri, Oct 16, 2015 at ...

📅 Original date posted:2015-10-16
📝 Original message:
On Fri, Oct 16, 2015 at 02:22:25PM +0100, Mats Jerratsch wrote:
> [...] an attacker could trick it into a fake network, [...]

How do you tell the difference between the "real" network and a "fake"
one? (ie, what does a Turing test for the lightning network look like?)

I think there's two things:

1) you can figure out a route to people you want to pay (and
vice-versa)

2) payments on those routes actually go through

Even better, you can test this! Get a couple of merchant ids you find
interesting, and pay 1 satoshi to each of them, setting the R value as
the (double) SHA256 of the decrypted onion message. [0]

If you spent 1 satoshi to each of 10 merchants every day for a year to
verify connectivity, that'd still only amount to about $0.01 USD total
at current exchange rates, so it seems pretty affordable. [1]

It only works if you actually setup a channel, though -- so you have to
lock some money into the channel for however many confirmations until
the channel activates, before you can test, plus the OP_CSV delay if
the test fails.

But I think that would let people trustlessly avoid "fake" lightning
networks, even with a sybil-esque attack; no extra infrastructure needed.

Cheers,
aj

[0] If you're already on the lightning network, and you're establishing
a new channel as backup, you can just pay yourself 1 satoshi to verify
connectivity. If you have friends on lightning, you could pay them
1 satoshi to verify connectivity rather than a random merchant too.

[1] Hmm, does forwarding 1 satoshi (2.6 10,000ths of a cent) make
sense, or would the CPU cycles cost more than the fees you'd make?
How much does it cost to forward a transaction? In python on my
laptop, I get about 1000 ECDH operations per second in python, and
290k AES ops over a 3kB onion per second, and about 77k SHA256 ops
per second. So just counting elliptic ops, forwarding a transaction
requires three ops: an ECDH on the onion message, and an ECDSA on
the commitment transaction to add the HTLC, and another sometime
later to remove it. So say 1/350th of a CPU-second. My linode costs
3c/hour and seems to be about half as fast on the SHA256 test, but
gives me two CPUs which evens it out. So so 3/60/60/350 cents is
about the cost of forwarding a single transaction, which is about
2.4e-8 dollars, which is currently about 9.1e-11 bitcoin, which
is 0.0091 satoshi. Conveniently lightning balances are denominated
in millisatoshi, so as long as yours increases by 9 or 10, you're
doing fine. 10 millisatoshi is 1% of 1 satoshi, so that seems like
the right order of magnitude.