Complex Scripts

Let's finish by learning about conditional clauses and flow control, and taking a look at some examples of complex scripts.

Differentiating between P2WPKH and P2WSH

In the previous two sections, we demonstrated two types of witness programs: Pay-to-Witness-Public-Key-Hash (P2WPKH) and Pay-to-Witness-Script-Hash (P2WSH). Both types of witness programs consist of a single byte version number followed by a longer hash. They look very similar, but are interpreted very differently: one is interpreted as a public key hash, which is satisfied by a signature and the other as a script hash, which is satisfied by a redeem script. The critical difference between them is the length of the hash:

The public key hash in P2WPKH is 20 bytes
The script hash in P2WSH is 32 bytes

This is the one difference that allows a wallet to differentiate between the two types of witness programs. By looking at the length of the hash, a wallet can determine what type of witness program it is, P2WPKH or P2WSH.