Ethereum: Redeem script. script hash, witness script and witness program

11 Feb Ethereum: Redeem script. script hash, witness script and witness program

Scripting Ethereum 101: Understanding Redemption Scripts, Witness Scripts, and Witness Programs

As a user of the Ethereum blockchain, it is important to understand the scripting language behind transactions, contracts, and other smart contract features. In this article, we will dive into the world of Ethereum scripting, focusing on two key concepts: redemption scripts, witness scripts, and witness programs.

What are scripts?

In Bitcoin, scripts are a way to execute complex logic using digital signatures. They are essentially self-contained blocks of code that can be executed by the network. In Ethereum, scripts are used for a variety of purposes, including:

• Event confirmation

• Smart contract execution

• Payment processing

Revenge Script: Special Case

A redemption script is a special Ethereum script that allows you to verify and confirm transactions. It is called a “buyback” because it is designed to buy back or “release” funds held in a contract or other smart contract.

The ransom script consists of two main parts:

• PubKeyHash: This is the public key used to sign the transaction.

• Script Bytes: This is the binary representation of the script, which contains the logic to verify and validate the transaction.

The syntax of the ransom script is as follows:

OP_DUP OP_HASH160  OP_EQUALVERIFY OP_CHECKSIG ...

Here is a breakdown of each component:

• OP_DUP: This is an instruction that copies the signature from the previous step.

• OP_HASH160: This specifies the public key used to sign the transaction.

• : This is the public key that is hashed and verified.

• OP_EQUALVERIFY: This verifies if the signature on the hash matches the expected signature.

• OP_CHECKSIG: This verifies that the original signature was created by the owner of the contract.

Witness Handwriting

A witness script, also known as a “witness program”, is a type of Ethereum script used for validation and confirmation. It is designed to verify online transactions and agreements without the need for additional scripts.

Witness programs are typically implemented using a combination of scripts and a witness program header. The header contains information about the witness program, including:

• Witness Program ID: This is the unique identifier assigned to the witness program.

• Script Signature: This is the digital signature associated with the witness program.

The syntax of the witness script is as follows:

0x... // Title of the witness program
OP_DUP OP_HASH160  OP_EQUALVERIFY ...
WITNESSE_Program_ID

Here is a breakdown of each component:

• 0x...: This is the hexadecimal representation of the witness program header.

• OP_DUP: This copies the signature from the previous step.

• OP_HASH160: This specifies the public key used to sign the transaction.

• : This is the public key that is hashed and verified.

• OP_EQUALVERIFY: This verifies if the signature on the hash matches the expected signature.

• WITNESSE_program_id: This contains information about the witness program, including its ID.

Witness Program Title

The witness program header contains information about the witness program, such as:

• Program Name: The name of the agreement or smart contract.

• Program Version

  : The version number of the contract or smart contract.

• Gas Limits: The maximum amount of gas as specified in the contract or smart contract.

The syntax of the witness program header is as follows:

0x... // Title of the witness program
OP_DUP OP_HASH160  OP_EQUALVERIFY ...
PROGRAM  PROGVERS [1..n] ...

Here is a breakdown of each component:

• 0x...: This is the hexadecimal representation of the witness program header.

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