<p>Objections that come to mind initially, I'm sure there are more:</p>
<ol>
<li><p>You don't want to split the hashing power into two halves because that would make it easier for an adversary to get 51% of that halve: 25% of the total or even less if the halves are not exactly 50-50.</p>
<p>The idea behind Proof of Work is to concentrate as much work as possible behind one and the same chain and make that the level-to-beat by an attacker.</p>
</li>
<li><p>If you force odd transactions into odd blocks (and vice versa) then you still have 10 minutes block times for all transactions.</p>
</li>
</ol>

CC BY-SA 3.0
2015-07-13T07:12:39.413Z
2015-07-13T07:12:39.413Z
2020-06-16T11:10:03.350Z
Jannes
<p>If the bitcoin protocol were changed so that the merkle root from block N-1 were replaced in block N by the two roots of blocks N-2 and N-3, then it would become possible to mine 2 blocks at a time in parallel and increase the block frequency compared to the time each block took to propagate. Each block would still get confirmed by 6 of the following 7 blocks. The block size variance could be controlled by requiring that transactions with odd hashes go into odd-numbered blocks and vice-versa. What would be the limitations of this variant protocol compared to the existing Bitcoin protocol, assuming nobody considered one confirmation to be much better than zero?</p>

CC BY-SA 3.0
2015-07-16T04:52:37.507Z
I don't think I understand your proposal. There are five fields in a Bitcoin block header: version, prevblock, merkle root, timestamp, and nonce. Which one are you proposing to modify, and how?
Nick ODell
CC BY-SA 3.0
2017-06-08T03:12:17.680Z
prevblock, by replacing it with two fields based on blocks N-2 and N-3.
Pr0methean
<blockchain><altcoin><blockchain-fork>
What if block N were based not on N-1 but on both N-2 and N-3?
Pr0methean
# What if block N were based not on N-1 but on both N-2 and N-3?

(Asked by: username_0 on 2015-07-13)

If the bitcoin protocol were changed so that the merkle root from block N-1 were replaced in block N by the two roots of blocks N-2 and N-3, then it would become possible to mine 2 blocks at a time in parallel and increase the block frequency compared to the time each block took to propagate. Each block would still get confirmed by 6 of the following 7 blocks. The block size variance could be controlled by requiring that transactions with odd hashes go into odd-numbered blocks and vice-versa. What would be the limitations of this variant protocol compared to the existing Bitcoin protocol, assuming nobody considered one confirmation to be much better than zero?

**Tags:** blockchain, altcoin, blockchain-fork

> **Comments:**
> **username_1**: I don't think I understand your proposal. There are five fields in a Bitcoin block header: version, prevblock, merkle root, timestamp, and nonce. Which one are you proposing to modify, and how?  
> **username_0**: prevblock, by replacing it with two fields based on blocks N-2 and N-3.  

---

## 1 answers

### Answer by username_2 on 2015-07-13. Score: 1

Objections that come to mind initially, I'm sure there are more:

1. You don't want to split the hashing power into two halves because that would make it easier for an adversary to get 51% of that halve: 25% of the total or even less if the halves are not exactly 50-50.

   The idea behind Proof of Work is to concentrate as much work as possible behind one and the same chain and make that the level-to-beat by an attacker.
2. If you force odd transactions into odd blocks (and vice versa) then you still have 10 minutes block times for all transactions.


---

