Ethereum: Why doesn’t the address contain a full ScriptPubKey for P2PKH transactions?
When sending transactions on Ethereum, users often want to include their private keys in the transaction data. However, when using public key hardware wallets or software wallets that support private key hardware (P2PKH) addresses, the address field of the transaction is represented as a script-encoded address that contains only part of the full public key.
This is called the “Partial ScriptPubKey” problem. In this article, we will examine why Ethereum does not provide a full ScriptPubKey for P2PKH transactions and explore possible solutions to address this limitation.
The Problem with Partial ScriptPubKeys
In P2PKH addresses, the sender’s private key is hashed using the Keccak-256 hash function with the “publickeyHash” field. This creates the public key used in the transaction. However, when representing the full script-encoded address on Ethereum, only a small portion of the public key is stored as a hexadecimal string.
The reason for this limitation lies in the way Ethereum’s Solidity scripting language implements P2PKH addresses. Solidity uses a compact representation of the private key to reduce memory usage and improve performance. However, this compact representation can result in truncated values when used with certain input types or libraries.
Why doesn’t Address contain a full ScriptPubKey?
When you create an Ethereum wallet using a software wallet like MetaMask or Trust Wallet, it typically stores only a portion of the full script-encoded address as the “Address” field. This is because the wallet may not be able to access the private key hash for all possible input types and libraries.
The following happens:
- The wallet creates a partial ScriptPubKey that represents the sender’s P2PKH address.
- The wallet stores only a small portion of this script-encoded address as the address field, typically 32 bytes (256 bits) long.
- When sending transactions over Ethereum, the wallet uses this shortened value to represent the full address in the transaction data.
How to work around the partial ScriptPubKey issue?
While Ethereum does not provide a full ScriptPubKey for P2PKH addresses, there are a few workarounds:
- Use a longer Keccak-256 hash: If you have control over the input type and library used by your software wallet, you can generate a longer Keccak-256 hash for your private key.
- Implement P2CO (P2PKH Coin): Some wallets support P2CO addresses, which contain the full public key in the transaction data. However, this option is not widely supported and may require additional setup steps.
- Use alternative wallets: If you are using a software wallet that does not support the full ScriptPubKey representation for P2PKH addresses, you should switch to an alternative wallet that does support these addresses.
Conclusion
The partial ScriptPubKey issue in Ethereum’s address format can be frustrating for users who rely on public key hardware wallets or software wallets that do not provide the full script-encoded address. However, there are workarounds and alternatives. Understanding why this limitation exists and exploring possible solutions will help you better manage your transactions and ensure seamless interactions with P2PKH-enabled wallets.
Related Resources
- Official Ethereum documentation on P2PKH addresses
- Solidity 0.8.x and above: Address field behavior
- MetaMask and Trust Wallet documentation to support full ScriptPubKey representation