The short version: nobody can rent a majority of this chain from the marketplaces today. On October 24 the three rental markets together listed 31.7 PH/s of BLAKE2b hash. The network runs at 42.55 PH/s. An attacker who rented every listed rig, and outbid every current renter to get it, would still bring less hash than the honest side has. The catch is that much of the rented hash is already mining this chain. An attacker who takes over Mining Rig Rentals’ running rigs adds nothing to the network. Up to half of it changes sides.
On October 8 Mining Stacker wrote that this chain “can also be 51% attacked by rentals right now.” This post reads the markets’ own pages to check.
Two words first
Hash is the guessing work miners do to find blocks, and hash rate is how fast they guess. The unit here is PH/s, petahash per second. One PH is a thousand TH, terahash, and rented rigs are priced by the TH.
A rental market lists rigs that miners offer. A listed rig is a promise. A live rig is one the market measures actually delivering hash. An available rig is live and not rented by anyone yet.
What was for rent on October 24
| Market | Available | Rented | Live | Price, BTC per TH per day |
|---|---|---|---|---|
| Mining Rig Rentals | 16.55 PH/s | 14.69 PH/s | 20.93 PH/s | 0.00002795, last rental |
| tidehash | 0 | 0.26 PH/s | 0.27 PH/s | about 0.000033 |
| routehash | 0.19 PH/s | 0 | 0.19 PH/s | 0.000029 to 0.000031 plus 2.5 percent |
| All three | 16.74 PH/s | 14.95 PH/s | 21.4 PH/s |
All three markets publish these numbers on their own pages. Mining Rig Rentals is nearly the whole market. In 30 days it filled 24,819 BLAKE2b rentals for 294 renters. Its page says this coin “requires a self hosted Bitcoin knots node and Datum Gateway.” The network’s 42.55 PH/s is from our node, the difficulty set on October 17.
Three ways to count the ceiling
Against the network’s 42.55 PH/s, an attacker could rent:
- What is free right now, nobody outbid: 16.7 PH/s, 39 percent of the network.
- What the rigs really deliver, live hash: 21.4 PH/s, 50 percent.
- Everything listed, every renter outbid: 31.7 PH/s, 74 percent.
The hash floor post priced three attacks. A week of mercenary hash at twice the network’s rate needs the attacker to bring 42.5 PH/s. A one-day 51 percent attack, with a small margin, needs 46.8. A week at four times needs 127.6. None of the three counts above reaches even the smallest of these. Listed hash is capacity on paper. A 58 PH/s listing appeared around October 20, was reported as fake, and was removed. What would change the first sentence of this post: 42.5 PH/s listed, or an attacker who owns 10.8 PH/s outright and rents everything else.
The catch
Those counts assume rented hash is added to an honest network. Mining Rig Rentals’ own banner says its renters mine this chain. So its rigs are already part of today’s 42.55. An attacker who takes over those rentals does not grow the network. The hash leaves the honest side and joins the attack.
If all 20.93 PH/s of that market’s live hash mines here today, an attacker holding it has 49 percent and everyone else 51. If the idle rigs point elsewhere, 43. The pages do not say which. Neither is a majority. Both are close. The number to watch is not how much hash is for rent. It is how much of today’s hash is rented.
The floor, rerun
The hash floor post asked a different question: below what honest hash rate does renting hash to attack this chain pay? Two inputs moved since.
Rent fell. The post used 0.00004 to 0.00006 BTC per TH per day. The last rental on October 24 was 0.000028, and that was also the lowest ask. Cheaper rent makes an attack cheaper, so the chain needs more honest hash to be safe. The floor rises.
The coin fell too. XBT closed at 0.0068 BTC on October 20 and 0.0045 on October 23. On October 24 it traded at 0.0048. A cheaper coin makes the attacker’s reward worth less. The floor falls.
The two nearly cancel. The floor for a week at twice the hash moved from 63 to 72 PH/s. Across today’s full range of rent and price, the chain sits under the floor in two of the four cases we ran, down from three. A four-times week under a 144-block difficulty window still loses money in every case. The verdict is the post’s: at the floor, not above it. This is a dated reading. The market moves by the hour.
The boycott, as arithmetic
The plan stated on the Knots Discord has two halves. Each pushes a different number.
Stop renting. Demand falls, so rent falls, and cheaper rent raises the floor. The rigs stay listed, so the ceiling does not move. Rigs that were rented become available, so more can be rented without outbidding anyone.
Stop listing. The ceiling shrinks one for one with the hash pulled off the market. Less supply raises the rent, and dearer rent lowers the floor.
Where a delisted rig goes is a third number. If its owner mines this chain with it, the network keeps the hash and the attacker has nothing to rent. If it switches to another coin or turns off, the network’s hash falls while the floor stays where rent and price put it.
The arithmetic says which way each half pushes. It does not say what to do.
The full tables, the readings and the code are in the repo. Ask and we will send them. Corrections welcome.
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