Re: [bitcoindev] [BIP Draft] Testnet 5

["'Pol Espinasa' via Bitcoin Development Mailing List" <bitcoindev@googlegroups.com>]

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Hi,


On Tuesday, June 2nd, 2026 at 5:02 PM, Saint Wenhao <saintwenhao@gmail.com> wrote:

> > I am sharing a BIP draft for a new Testnet5.
>
> Interesting. Does it mean, that testnet4 fixes won't be done? https://batmanbytes.github.io/testnet4-softfork/

They won't (or at least it is not what we are proposing here), I agree with Antoine that a fresh start is better than just pile up workarounds.
Sometimes the cure is worse than the disease.

> > For the Pubkey field, use a recent Bitcoin mainnet block hash.
>
> Do you mean taking the hash of the block, and using it as x-value for a public key? Then, it could be potentially spendable, if it would be a valid secp256k1 point, and people would send more coins to it, or unspendable, if it would be outside of the curve. For example:
>
> spendable: 0200000000000000000001799c6f72ebe5ebc6b18fd5cdf8bd3697b8d73d01b084 OP_CHECKSIG
> unspendable: 02000000000000000000013ac2955a2b6029bc1a86ab4b19e01e8030ceb0eeb2ae OP_CHECKSIG
> unspendable: 00000000000000000001799c6f72ebe5ebc6b18fd5cdf8bd3697b8d73d01b084 OP_CHECKSIG
>
> Also, if the size of the stack push would be different than 33 or 65 bytes, then it would be unspendable (for example if it would take 32 bytes, like block hashes, and would be followed by OP_CHECKSIG, to invalidate it, or if it would start with OP_RETURN).

yes, as per the original text in the draft: "the output is provably unspendable". The idea comes from: https://github.com/bitcoin/bitcoin/pull/29775#issuecomment-2093516015, https://github.com/bitcoin/bitcoin/pull/29775#issuecomment-2095786951, https://github.com/bitcoin/bitcoin/pull/29775#issuecomment-2099974737


> > Difficulty: 0x1d00ffff
>
> I wonder, how quickly it would be listed on exchanges, and traded. Because historically, new testnets were launched, when that happened. But today, new coins are listed faster, than they are replaced. Which would give the creator with any ASIC an incentive, to mine initial 30k or so blocks, keep them for a while, and then sell for BTCs, when the coin will be listed.

That is a risk, but I personally don't think there is any real solution for that. It is impossible to avoid people selling coins.
I hope the risk of resetting the network or starting a new one (as we did multiple times, and we are suggesting here) is enough for coins to not have "much" value.

> Also, I wonder if testnet5 will have any premine. Previous attempt to create testnet5: https://bitcointalk.org/index.php?topic=5543921

It will not, using a mainnnet block hash in the Pubkey field acts as an anti-premine-commitment.

> > Testnet 5 also does not apply the difficulty exception rule from Testnet 3 or Testnet 4 requires.
>
> It would be nice to simplify the code, and remove that rule completely from sources, but it would probably take a while to deprecate testnet3 and testnet4.

I agree that might take time, but that is a node client implementation detail :)

> wt., 2 cze 2026 o 13:27 'Pol Espinasa' via Bitcoin Development Mailing List <bitcoindev@googlegroups.com> napisał(a):
>
> > Dear list,
> > I am sharing a BIP draft for a new Testnet5.
> > People are complaining about Testnet4 being difficult to use, the new testnet also works as a miner playground for BIP54, we are killing two birds with one stone.
> >
> > You can find the full text to read and comment on in the following draft PR: https://github.com/fjahr/bips/pull/2
> > Feel free to leave inline comments there or respond here on the list.
> >
> >
> >
> >
> > Pol
> >
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