P2PK in Coinbase Transactions

Although P2PK is mostly obsolete for standard user payments, it remains a massive part of Bitcoin's history because of its dominance in the early Coinbase Transactions (block rewards).

1. The Default for Mining

In the early versions of the Bitcoin software (0.1.0 to 0.3.0), the miner's reward was always sent to a P2PK output.

• When Satoshi Nakamoto was mining the first 30,000+ blocks, every single one of those 50 BTC rewards was locked in a P2PK script.

• This is why we know Satoshi's public keys, even though we don't know his identity.

2. The Satoshi Millions

It is estimated that Satoshi Nakamoto owns approximately 1.1 million BTC.

• The vast majority of these coins are held in P2PK outputs that have never been spent.

• Because they are P2PK, these coins are effectively "Quantum Vulnerable" as discussed in the previous section. If a quantum computer ever breaks secp256k1, the Satoshi coins would likely be the first target.

3. Why did miners switch?

As the network grew, developers realized that P2PK was inefficient.

• Storage: P2PK ScriptPubKeys take up ~67 bytes. P2PKH takes up ~25 bytes.

• Privacy: Using a public key directly makes it easier to link identities. Eventually, mining software updated to support P2PKH, and eventually SegWit.

4. Identifying P2PK Today

You can still find P2PK transactions occurring today, though they are usually created by custom software or "legacy" mining pools. Any transaction that doesn't start with a standard address but instead shows a raw hex script ending in ac is likely a P2PK spend.

Block Era	Reward Script Type	Status
Blocks 0 - 30,000	Almost 100% P2PK	Dormant / Vulnerable
Blocks 30,000 - 481,824	Transition to P2PKH	Spent / Standard
Modern Era	SegWit / Taproot	Secure / Efficient

In the final section, we will build a Python P2PK Auditor.