[feat] Check if transaction output is provably unspendable

[m-kus]

There are cases when we can say with 100% guarantee that a particular output cannot be spent.
Such cases include:

• Pubkey script begins with OP_RETURN
• Pubkey script size is larger than the maximum allowed
• Two coinbase transactions in the past (BIP-30)

Implement three helper functions:

• is_pubscript_unspendable(pubscript: @ByteArray) in validation/transaction
• is_bip30_unspendable(block_height: u32) in validation/coinbase
• validate_bip30_block_hash(block_height: u32, block_hash: @Digest) in validation/block (ensures that these two exceptional blocks in the past has exact height/hash pair match)

Call validate_bip30_block_hash in validate_and_apply.

References:

• https://github.com/bitcoin/bitcoin/blob/a5e99669ccfe0683749ce2e2b21732a359ef62d7/src/script/script.h#L560
• https://github.com/bitcoin/bitcoin/blob/a5e99669ccfe0683749ce2e2b21732a359ef62d7/src/validation.cpp#L6310
• https://github.com/bitcoin/bitcoin/blob/a5e99669ccfe0683749ce2e2b21732a359ef62d7/src/index/coinstatsindex.cpp#L153

[mubarak23]

@m-kus can i give this a go

kindly assign

[onlydustapp]

Hey @mubarak23!
Thanks for showing interest.
We've created an application for you to contribute to Raito - Bitcoin ZK Client.
Go check it out on OnlyDust!

[Gerson2102]

I would like to try this sir!

[onlydustapp]

Hey @Gerson2102!
Thanks for showing interest.
We've created an application for you to contribute to Raito - Bitcoin ZK Client.
Go check it out on OnlyDust!

[JoE11-y]

Can I take a look at this @m-kus.

[Sravya-212]

I am applying to this issue via OnlyDust platform.

My background and how it can be leveraged

I am Blockchain developer with 2 years of experience, I have created and deployed many decentralized projects by mainly focussing on the the Smart Contracts development and secure transactions, I have built DApps, DeFi, which are realtime projects.

How I plan on tackling this issue

I would create a function that works in case of the following
Pubkey script begins with OP_RETURN
Pubkey script size is larger than the maximum allowed
Two coinbase transactions in the past (BIP-30)
and returns an event telling the user why the output cannot be spent by implementing the helper functions given into the specific paths.

[m-kus]

@Gerson2102 how is the progress on this task?

[Gerson2102]

Currently working on it. I already have the first function. The two left don't know how to do them. I was about to start asking questions about it. But did not have time recently, so maybe at night i wil start working again on it and I'll prepare questions for it.

[Sravya-212]

@Gerson2102 @m-kus can I join the task too, you don’t have to pay me or anything, I just want to contribute and learn, please let me help in this.

[m-kus]

@Sravya-212 no worries, there's gonna be more good first issues

[Jemiiah]

@m-kus would love to contribute to upcoming issues as well