Processing bitcoin reward block's input transaction

Question

I'm parsing the block response of my bitcoin node and everything is going ok. The only thing I don't understand is how to parse the input transaction of the block reward.

This is the array that I see as the signature_script of the 4th block of the Bitcoin blockchain, which has only one transaction and is the signature_script which each byte is in it's decimal form: <<4,255,255,0,29,1,3>>.

What does this mean? I could not found information about it in the documentation.

Answer 1

This is the scriptSig of a coinbase transaction (the first transaction in every block is special; it doesn't actually spend anything but brings new coins into existence).

Coinbase transactions have a number of special rules that apply to them:

• They must be the first transaction in a block, and cannot occur anywhere else.
• They must have exactly one input, for which:
  • The prevout must have hash 0000...0000 and vout index 0xFFFFFFFF.
  • The scriptSig must be between 2 and 100 bytes long, but otherwise has no meaning. Miners typically use this space to store what is called an extranonce, to be able to grind through more hashes per second then the block header nonce space allows for.
  • Since the activation of BIP34 in 2012 (which your block predates), the coinbase scriptSig must start with a push of the block height.
• They can claim the block's subsidy and all fees paid in the block (implicitly).
• They must have 1 or more outputs like every other transaction, determining where the mining rewards get paid to.

So in short, this script has no actual meaning, except for being space miners can fill in as they wish.