BA-06 · LESSON 09

P2PK, P2PKH, P2MS, P2SH, and OP_RETURN

KEY DEFINITIONS

Terms used in this lesson

P2PK: Pay to Public Key, an early Bitcoin output template that places a complete public key in the locking script.
P2PKH: Pay to Public Key Hash, a legacy Bitcoin output template that commits to the hash of a public key.
P2MS: Pay to Multisig, a Bitcoin Script template that requires a stated number of signatures from a list of public keys.
P2SH: Pay to Script Hash, a legacy Bitcoin output template that commits to a redeem script.
OP_RETURN: A Bitcoin Script operation commonly used to create an unspendable output carrying a small amount of data.
ASM: Assembly-style text that writes Bitcoin Script operations and pushed data in a human-readable order.
Hash160: SHA-256 followed by RIPEMD-160, producing the 20-byte hash used by several Bitcoin spending conditions.
CHECKSIG: The Bitcoin Script operation that checks whether a signature is valid for the required public key and transaction message.
DUP: The short operation name for copying the top Bitcoin Script stack item.
EQUALVERIFY: The short operation name for comparing two Bitcoin Script values and failing immediately when they differ.
CHECKMULTISIG: The Bitcoin Script operation that checks a threshold number of ordered signatures against a list of public keys.
EQUAL: The short operation name for comparing two Bitcoin Script byte strings and pushing true or false.
UTXO: Unspent transaction output: one discrete chunk of bitcoin that can be used as a transaction input.

Compare the exact assembly, serialized bytes, spend data, standard uses, and failure boundary for Bitcoin's classic Script templates.

35 min Difficulty 2/5 Not started

VISUAL MODEL

See the whole mechanism before going step by step

Use the diagrams to orient yourself. Then the guided explanation below teaches every part in depth.

4 explanatory views

CONCEPT-SPECIFIC MAP · classic script templatesClassic templates commit keys, key hashes, scripts, or unspendable dataSelect any state to inspect its exact role.

RELATIONSHIP MAPOrdered validation pipeline

01
P2PK<pubkey> CHECKSIG
The output directly reveals and commits a public key.
02
P2PKHDUP HASH160 ... CHECKSIG
The spend reveals a public key whose HASH160 must match before CHECKSIG.
03
P2MSM <keys> n CHECKMULTISIG
Bare multisig exposes the complete threshold and public-key set.
04
P2SHHASH160 <script hash> EQUAL
The exact redeem script must match its hash and then execute successfully.
05
OP_RETURNProvably unspendable data
OP_RETURN stops execution and is commonly bounded by relay policy.

Rule shown: Exact Script bytes determine the revealed spend data and the first stack predicate that can fail.

STAGE 1 OF 5P2PK: <pubkey> CHECKSIG

The output directly reveals and commits a public key.

Governing relationship: Exact Script bytes determine the revealed spend data and the first stack predicate that can fail. Complete path: 1. P2PK, <pubkey> CHECKSIG. The output directly reveals and commits a public key. 2. P2PKH, DUP HASH160 ... CHECKSIG. The spend reveals a public key whose HASH160 must match before CHECKSIG. 3. P2MS, M <keys> n CHECKMULTISIG. Bare multisig exposes the complete threshold and public-key set. 4. P2SH, HASH160 <script hash> EQUAL. The exact redeem script must match its hash and then execute successfully. 5. OP_RETURN, Provably unspendable data. OP_RETURN stops execution and is commonly bounded by relay policy.

1. State transitionWhat exists, what changes, and what results

BEFORE

Alice can choose P2PKH to key A or P2SH to a 2-of-3 redeem script.

MECHANISM

P2PK is <pubkey> CHECKSIG. P2PKH is DUP HASH160 <20-byte key hash> EQUALVERIFY CHECKSIG and is spent with a signature plus matching public key.

AFTER

Templates differ in what they reveal at creation, what they commit, and what spending data must later prove.

Text equivalent: Starting from Alice can choose P2PKH to key A or P2SH to a 2-of-3 redeem script. The mechanism begins when P2PK is <pubkey> CHECKSIG. P2PKH is DUP HASH160 <20-byte key hash> EQUALVERIFY CHECKSIG and is spent with a signature plus matching public key. The resulting lesson is Templates differ in what they reveal at creation, what they commit, and what spending data must later prove.

2. Mechanism pathSelect a stage to inspect its job

STAGE 1 OF 5

Execute P2PK and P2PKH

P2PK is <pubkey> CHECKSIG. P2PKH is DUP HASH160 <20-byte key hash> EQUALVERIFY CHECKSIG and is spent with a signature plus matching public key.

Complete path: 1. Execute P2PK and P2PKH: P2PK is <pubkey> CHECKSIG. P2PKH is DUP HASH160 <20-byte key hash> EQUALVERIFY CHECKSIG and is spent with a signature plus matching public key. 2. Execute bare P2MS: A standard bare multisig form is m <pubkeys> n CHECKMULTISIG. The historical extra stack pop requires a leading dummy item in spending data. 3. Commit a redeem script with P2SH: P2SH is HASH160 <20-byte script hash> EQUAL. The spender pushes arguments plus the exact serialized redeem script, whose hash is checked before that script executes. 4. Recognize OP_RETURN: OP_RETURN immediately fails if the output is spent, so the output can be removed from the spendable UTXO set. Relay policy limits common data-carrier forms even though consensus and policy are distinct. 5. Trace raw bytes and first failure: For each template, decode opcodes, push lengths, committed bytes, stack inputs, stack transitions, signature commitment, and the first opcode that fails after a mutation.

3. Rule and failure boundaryWhat accepts the result and where it can stop

ACCEPTED PATH

The serialized locking script selects exact stack rules, and every pushed key, signature, script, threshold, and hash must satisfy them under the transaction signature context.

CHANGED CONDITION

A matching address encoding cannot rescue a different redeem script, wrong public key, insufficient multisig signatures, or a transaction message not covered by the supplied signature.

Important distinction: P2SH makes any redeem script valid as long as its address checksum is correct. The address helps construct a hash commitment. Spending still requires the exact redeem script to match that hash and then execute successfully.

Text equivalent: The accepted path is enforced by The serialized locking script selects exact stack rules, and every pushed key, signature, script, threshold, and hash must satisfy them under the transaction signature context. If the required condition changes, A matching address encoding cannot rescue a different redeem script, wrong public key, insufficient multisig signatures, or a transaction message not covered by the supplied signature.

Loading lesson visuals...

Learn the idea

Bitcoin's classic output templates are exact scripts, not address labels. P2PK locks directly to a public key. P2PKH commits to a public-key hash. P2MS places a visible multisignature threshold in Script. P2SH commits to the HASH160 of a redeem script. OP_RETURN makes its output provably unspendable and carries bounded application data under relay policy.

GUIDED EXPLANATION1/5 ideas inspected

Execute P2PK and P2PKH

P2PK is <pubkey> CHECKSIG. P2PKH is DUP HASH160 <20-byte key hash> EQUALVERIFY CHECKSIG and is spent with a signature plus matching public key.

The worked example follows the explanation

Inspect every idea above to open it.

Important distinction“P2SH makes any redeem script valid as long as its address checksum is correct.”

The address helps construct a hash commitment. Spending still requires the exact redeem script to match that hash and then execute successfully.

FINISH LEARNING FIRST

The questions unlock after every required learning activity

Inspect every guided idea, open the worked example, rebuild its mechanism, and complete the deterministic lesson tool. Your progress is saved automatically.