P2PK ScriptPubKey Structure

The beauty of P2PK lies in its simplicity. It is the most straightforward implementation of a "Smart Contract" in Bitcoin. It uses only two components: a piece of data (the public key) and one opcode.

1. The Locking Script (ScriptPubKey)

The script that "locks" the output looks like this: [Public Key Bytes] OP_CHECKSIG

• Public Key: Usually a 65-byte uncompressed key (starting with 04) or a 33-byte compressed key (starting with 02 or 03).

• OP_CHECKSIG: The instruction that tells the Bitcoin Virtual Machine to verify a signature against the provided public key.

2. The Unlocking Script (ScriptSig)

To spend a P2PK output, the owner only needs to provide one thing in their input: [Signature]

• They don't need to provide the public key in the ScriptSig because it is already provided in the ScriptPubKey.

3. The Execution Logic

When a node verifies the transaction, it combines the two scripts: [Signature] [Public Key Bytes] OP_CHECKSIG

1. The Signature is pushed onto the stack.

2. The Public Key is pushed onto the stack.

3. OP_CHECKSIG pops both items, checks if the signature is valid for that public key, and pushes 1 (Success) or 0 (Failure) back onto the stack.

4. Raw Hex Example

A typical P2PK ScriptPubKey in raw hex would look like this: 41 04ae6a19...[65 bytes of key]... ac

• 41: The push-data opcode (65 bytes in decimal).

• 04...: The uncompressed public key.

• ac: The hex code for OP_CHECKSIG.

Component	Opcode / Value	Length
Push Data	0x41 (or 0x21)	1 Byte
Public Key	The Raw Key	33/65 Bytes
Operation	0xac (OP_CHECKSIG)	1 Byte

In the next section, we will discuss Quantum Security and the difference between P2PK and P2PKH.