Understanding Ethereum Script Output: A Guide to ScriptPubKey, ScriptSig, RedeemScript, and Witness Scripts
The Ethereum scripting framework is a powerful tool that allows developers to create custom transactions and contracts. The core of this framework is the various script outputs that are used in these transactions. In this article, we will look at the different types of script outputs and their corresponding scripts.
ScriptPubKey: A Universal Address Format
A ScriptPubKey (SPK) is a unique address format used to identify Ethereum addresses. It is a combination of a private key, a public key, and a version number. Here’s how it works:
- Public Key:
The first two bytes of the SPK represent the public key.
- Version Number: The next byte indicates the version of the Ethereum standard (currently 1).
- Private Key: The last 4 bytes are the private key.
ScriptSig: Signatures and Verification
A ScriptSig is a signature that verifies the authenticity of a transaction. It is defined by the following parameters:
- PubKey: The public key used to sign the transaction.
- SigHash: A hash of the transaction data encrypted with the private key.
The format of a ScriptSig looks like this:
0x00000f3d... (Signature)
`
RedeemScript: Payment Verification
A “RedeemScript” is a script that verifies the validity of a payment. It is used to verify that the transaction was successfully processed and properly paid. The format of the RedeemScript looks like this:
0x00000f3d... (Signature)
1x... (Transaction hash)
2x... (Sender's public key)
3x... (Sender's private key)
4x... (Block number and timestamp)
5x... (difficulty level)
6x... (Amount paid)
7x... (Sender's address)
8x... (Recipient's address)
9x... (gas limit)
10x... (gas price)
Witness script: signs transactions
A witness script is a type of script that signs transactions on behalf of the sender. It is used to verify the authenticity and integrity of a transaction, even after it has been mined. The format of a witness script looks like this:
0x00000f3d... (Signature)
1x... (transaction data hash)
2x... (Sender's public key)
3x... (Sender's private key)
4x... (Block number and timestamp)
5x... (difficulty level)
6x... (Amount paid)
7x... (Sender's address)
8x... (Recipient's address)
9x... (gas limit)
10x... (gas price)
Witness program: signatures and verification
A witness program is a type of script that signs transactions on behalf of the sender. It is used to verify the authenticity and integrity of a transaction, even after it has been mined. The format of the witness program looks like this:
0x00000f3d... (Signature)
1x... (transaction hash)
2x... (Sender's public key)
3x... (Sender's private key)
4x... (Block number and timestamp)
5x... (difficulty level)
6x... (Amount paid)
7x... (Sender's address)
8x... (Recipient's address)
9x... (gas limit)
10x... (gas price)
To summarize, ScriptPubKey is used to establish Ethereum addresses, ScriptSig verifies the authenticity of transactions. RedeemScript is used to verify the integrity of payments, and witness scripts sign transactions on behalf of senders.
Output Types
Ethereum supports several output types, including:
- P2PKH: Private Key Based Address Format.
- P2SH: Script Hash Address Format (used by SegWit).
- BIP39: Base58 Validation Function (used to derive seeds).
- BIP44: 32 Byte Origin Output Format (used to store private keys).
Each output type has its own set of scripts, including ScriptPubKey, ScriptSig, RedeemScript, and Witness. Understanding these different script outputs is essential to building secure and efficient Ethereum applications.