About Ethereum Script Outputs: A Guide to ScriptPubKey, ScriptSig, RedeemScript, and Witness Scripts
The Ethereum scripting system is a powerful tool that allows developers to create custom transactions and contracts. At the heart of this system are the various script outputs used in these transactions. In this article, we will dive into the different types of script outputs and their associated 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 are the public key.
- Version Number: The next byte specifies 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: The hash of the transaction data, encrypted with the private key.
The ScriptSig format looks like this:
0x00000f3d... (Signature)
RedeemScript: Payment Verification
A RedeemScript is a script that verifies the validity of a payment. It is used to check whether a transaction has been processed correctly and paid correctly. The RedeemScript format is as follows:
0x00000f3d... (Signature)
1x... (Hash of transaction data)
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... (Fuel limit)
10x... (Fuel price)
Witness script: signing 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 the Witness script is as follows:
0x00000f3d... (Signature)
1x... (Hash of the transaction data)
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... (Fuel limit)
10x... (Fuel 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 is as follows:
0x00000f3d... (Signature)
1x... (Hash of transaction data)
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)
In summary, ScriptPubKey is used to identify Ethereum addresses, while ScriptSig verifies the authenticity of transactions. RedeemScript is used to verify the integrity of the payment, and Witness scripts sign transactions on behalf of senders.
Output Types
Ethereum supports several output types, including:
- P2PKH: A private key-based address format.
- P2SH: A script hash-based address format (used for SegWit).
- BIP39:
A base58 control function (used for seed derivation).
- BIP44: A 32-byte seed derivation format (used for private key storage).
Each output type has its own set of scripts, including ScriptPubKey, ScriptSig, RedeemScript, and Witness. Understanding these different script outputs is essential for building secure and efficient Ethereum-based applications.