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Part of this post addresses the economics of creating a 6 block re-org. This makes sense as 6-confimations is the standard for Bitcoin finality today. However,

Part of this post addresses the economics of creating a 6 block re-org. This makes sense as 6-confimations is the standard for Bitcoin finality today. However, as Bitcoin's security inevitably weakens over the coming years due to diminishing miner rewards (denominated in BTC), I believe this "6-confimation" acceptance policy will change to include not only the number of confirmations, but the timing of those confirmations as well. Consider a scenario where an exchange deciding whether a tx with 6-confirmations that took 4 hours to arrive (this happens occasionally) is safe to consider finalized/settled. Even though 6-confimations may be considered safe by today's acceptance policies, this tx would still have a high probability of double spend due to the assumed 4-hour long wait for the 6 confirmations (as the attacker would have 4 hours to produce 7 blocks instead of the normal/expected 1 hour). Instead of ignoring block interarrival timing, it may make sense to include block timing as part of an acceptance policy. So, going forward Bitcoin acceptance policies may change from today's 6-confirmation standard to something more complicated that involves the amount of time those blocks took to arrive. This would significantly enhance Bitcoin's double spending resistance without adding/altering any code and may give the network a much needed security boost in the coming years to prevent the attack discussed in the post.

mrb 9mo ago
"Bitcoin's security inevitably weakens over the coming years due to diminishing miner rewards (denominated in BTC)" That's incorrect. Security scales with USD-denominated rewards, not BTC-denominated. And there are 16 years of real-world data showing they have been generally increasing, so a healthy sign that the Bitcoin experiment is working: https://newhedge.io/bitcoin/block-reward-per-block https://newhedge.io/bitcoin/block-reward-per-block And not only that, but rewards are still expected to stabilize even when measured in BTC (thereby not relying on an increase of BTC's price) as they are progressively composed more and more of tx fees instead of newly mined BTC. It's puzzling to me why some still don't understand the systemic incentives that make all this work as it has for 16 years and counting...
- free_bip 9mo ago
  How are you so confident that it will never weaken? Especially since there will come a time when the block reward is literally 0.
  - mrb 9mo ago
    Tx fees make up a bigger and bigger fraction of miner rewards over time.
    - officialchicken 9mo ago
      Rewards are also a permanent infinite money glitch that last in perpetuity? Or won't be changed in the future?
    - rcxdude 9mo ago
      Is a store of value that requires a significant fraction of it be eaten up by transaction fees to maintain security going to be actually useful in the long term?
      - _heimdall 9mo ago
        With regards to transaction fees, bitcoin is already not particularly useful today. It can make sense to be used as an alternative to wire transfers where you only occasionally send a transaction, but it isn't useful as a currency and any day to day transactions have to happen off chain and not use bitcoin at all.
        rcxdude 9mo ago
        Right, which is why one has to wonder who's going to want to pay enough transaction fees to secure the network.
    - jcfrei 9mo ago
      transaction fees are not increasing though, so they can't offset miner rewards. they have been in the $100k-$200k per day range for a long time, with only occasional breakouts: https://www.blockchain.com/explorer/charts/transaction-fees-usd https://www.blockchain.com/explorer/charts/transaction-fees-... and the trend is not to the upside. in fact with the arrival of ETFs in 2024 the trend is clearly downwards.
copirate 9mo ago
If the attacker is waiting for a lucky event to occur (finding more blocks than others while having less than 51% of the mining power) it means that they are constantly wasting mining time. That in itself is a huge cost (operational cost and block rewards thrown away), but it also means that they can't predict when it will happen. A double spend attack must be planned in advance because the first transaction must occur at the beginning of the attack. I'm not sure how they could constantly try double spends without risking losing the money each time the attack doesn't happen. I don't see how it could be profitable. If it can't be profitable, then the risk of someone doing it is pretty low. If they already have the necessary hardware, they'd be much better off mining.
- Majromax 9mo ago
  > I'm not sure how they could constantly try double spends without risking losing the money each time the attack doesn't happen. If you're not trying to profit from the double spend itself but rather from a collapse following a proven double-spend, you can double-spend the bitcoins to yourself.
ur-whale 9mo ago
> However, as Bitcoin's security inevitably weakens over the coming years due to diminishing miner rewards (denominated in BTC), Says you, without a hint of a rationale backing your argument. It seems to me that the historical hashing rate curve tells a different story. And block rewards have been diminishing regularly (and very predictably) pretty much since day one.
- tromp 9mo ago
  The hashing rate is not directly relevant. That's roughly proportional to the daily dollar value of the reward times the efficiency of the leading mining hardware. The latter has gone up many orders of magnitude over the years. > block rewards have been diminishing regularly That's exactly what the poster you're replying to argued; the BTC denominated block subsidy halves every 4 years, and so without a corresponding doubling in price, the bitcoin security budget keeps diminishing, at least until tx fees start to dominate the subsidy.
nathias 9mo ago
you can accept bitcoin at any confirmation you want, it isn't a policy
- coldcity_again 9mo ago
  in bitcoin terminology it is actually called policy rather than consensus, meaning you can choose your own config and still meet consensus rules.
_heimdall 9mo ago
> This would significantly enhance Bitcoin's double spending resistance without adding/altering any code I would have expected such security rules are part of the miner code, no? Don't they need to consider rules related to the comparative security level of a chain when decided which chain to follow when multiple exist?

mrb 9mo ago

"Bitcoin's security inevitably weakens over the coming years due to diminishing miner rewards (denominated in BTC)" That's incorrect. Security scales with USD-denominated rewards, not BTC-denominated. And there are 16 years of real-world data showing they have been generally increasing, so a healthy sign that the Bitcoin experiment is working: https://newhedge.io/bitcoin/block-reward-per-block https://newhedge.io/bitcoin/block-reward-per-block And not only that, but rewards are still expected to stabilize even when measured in BTC (thereby not relying on an increase of BTC's price) as they are progressively composed more and more of tx fees instead of newly mined BTC. It's puzzling to me why some still don't understand the systemic incentives that make all this work as it has for 16 years and counting...

free_bip 9mo ago
How are you so confident that it will never weaken? Especially since there will come a time when the block reward is literally 0.
- mrb 9mo ago
  Tx fees make up a bigger and bigger fraction of miner rewards over time.
  - officialchicken 9mo ago
    Rewards are also a permanent infinite money glitch that last in perpetuity? Or won't be changed in the future?
  - rcxdude 9mo ago
    Is a store of value that requires a significant fraction of it be eaten up by transaction fees to maintain security going to be actually useful in the long term?
    - _heimdall 9mo ago
      With regards to transaction fees, bitcoin is already not particularly useful today. It can make sense to be used as an alternative to wire transfers where you only occasionally send a transaction, but it isn't useful as a currency and any day to day transactions have to happen off chain and not use bitcoin at all.
      - rcxdude 9mo ago
        Right, which is why one has to wonder who's going to want to pay enough transaction fees to secure the network.
  - jcfrei 9mo ago
    transaction fees are not increasing though, so they can't offset miner rewards. they have been in the $100k-$200k per day range for a long time, with only occasional breakouts: https://www.blockchain.com/explorer/charts/transaction-fees-usd https://www.blockchain.com/explorer/charts/transaction-fees-... and the trend is not to the upside. in fact with the arrival of ETFs in 2024 the trend is clearly downwards.

copirate 9mo ago

If the attacker is waiting for a lucky event to occur (finding more blocks than others while having less than 51% of the mining power) it means that they are constantly wasting mining time. That in itself is a huge cost (operational cost and block rewards thrown away), but it also means that they can't predict when it will happen. A double spend attack must be planned in advance because the first transaction must occur at the beginning of the attack. I'm not sure how they could constantly try double spends without risking losing the money each time the attack doesn't happen. I don't see how it could be profitable. If it can't be profitable, then the risk of someone doing it is pretty low. If they already have the necessary hardware, they'd be much better off mining.

Majromax 9mo ago
> I'm not sure how they could constantly try double spends without risking losing the money each time the attack doesn't happen. If you're not trying to profit from the double spend itself but rather from a collapse following a proven double-spend, you can double-spend the bitcoins to yourself.

ur-whale 9mo ago

> However, as Bitcoin's security inevitably weakens over the coming years due to diminishing miner rewards (denominated in BTC), Says you, without a hint of a rationale backing your argument. It seems to me that the historical hashing rate curve tells a different story. And block rewards have been diminishing regularly (and very predictably) pretty much since day one.

tromp 9mo ago
The hashing rate is not directly relevant. That's roughly proportional to the daily dollar value of the reward times the efficiency of the leading mining hardware. The latter has gone up many orders of magnitude over the years. > block rewards have been diminishing regularly That's exactly what the poster you're replying to argued; the BTC denominated block subsidy halves every 4 years, and so without a corresponding doubling in price, the bitcoin security budget keeps diminishing, at least until tx fees start to dominate the subsidy.

nathias 9mo ago

you can accept bitcoin at any confirmation you want, it isn't a policy

coldcity_again 9mo ago
in bitcoin terminology it is actually called policy rather than consensus, meaning you can choose your own config and still meet consensus rules.

_heimdall 9mo ago

> This would significantly enhance Bitcoin's double spending resistance without adding/altering any code I would have expected such security rules are part of the miner code, no? Don't they need to consider rules related to the comparative security level of a chain when decided which chain to follow when multiple exist?