Chapter 4 assessment 2

1. To spend a UTXO with a P2PKH script, what is needed in the scriptSig?

   • A valid digital signature and the parent TXID

   • The hash of the public key in the output scriptPubKey

   • A valid digital signature and the public key corresponding to the public key hash

   • The hash of the digital signature that spends the output and a public key

2. Why do we need to add a junk data item in a P2MS script?

   • Because the protocol was fixed with a bug in it which can't be removed because it is set in stone

   • Because we need a way to insert arbitrary data into multisig transactions

   • It's not actually junk, but part of a hidden feature that Satoshi never finished

   • It helps to solve threshold signature calculations

3. What is the limit of keys/signatures that a P2MS script can check?

   • 2 signatures checked against 3 keys

   • 10 signatures checked against 10 keys

   • 100 signatures against 200 keys

   • There is no limit within the protocol

4. What benefit does the P2PKH script have over P2PK and P2SH

   • In P2PKH it is much more difficult to guess the correct signature and steal funds

   • Both P2PK and P2SH have proven security issues and should never be used

   • P2PKH enhances the user's privacy by blending the best of both P2PK and P2SH

   • There is no benefit, and the choice is all about utility