What is a Bitcoin Pay-to-Witness-Script-Hash (P2WSH)?

Bitcoin Pay-to-Witness-Script-Hash (P2WSH) is a type of transaction output script used in the Bitcoin protocol to enable the spending of bitcoins. It is part of the Segregated Witness (SegWit) upgrade introduced to the Bitcoin network in 2017.

P2WSH transactions involve the following components:

1. **Witness Program**: A witness program is a short script that serves as the spending condition for a Bitcoin transaction output. In the case of P2WSH, the witness program is a hash of a redeem script, which contains the spending conditions (e.g., signatures required) encoded in a script.

2. **Script Hash**: The witness program is hashed to generate a unique script hash, which is used as the identifier for the spending conditions. This hash is known as the Witness Script Hash (WSH).

3. **Transaction Output**: A P2WSH transaction output contains the Witness Script Hash (WSH) as the locking condition, indicating that the bitcoins can only be spent if the spending transaction provides the corresponding witness data (e.g., signatures) that satisfies the spending conditions specified in the redeem script.

4. **Witness Data**: When spending bitcoins from a P2WSH output, the spending transaction must include the witness data, which consists of the redeem script and any additional data required to satisfy the spending conditions specified in the redeem script.

P2WSH provides several benefits over traditional Pay-to-Script-Hash (P2SH) transactions, including increased security, improved scalability, and enhanced flexibility for future protocol upgrades. It allows for more efficient use of block space, as witness data is segregated from the transaction data, resulting in smaller transaction sizes and lower fees. Additionally, P2WSH supports advanced scripting capabilities, enabling more complex smart contracts and multi-signature schemes.

Overall, P2WSH is a key feature of the Segregated Witness (SegWit) upgrade to the Bitcoin protocol, designed to improve the security, scalability, and functionality of Bitcoin transactions.