Ethereum: Why is the signature hash Different for each input in a multi-input transaction?
In Ethereum, when a multi-input transaction is executed, the signature hash of the transaction differs from the input hash. This Might Seem Counterintuitive at First, But It’s Essential to Understand Why This Design Choice was made.
BIP 14: Subses and signature hashes
Ethereum’s Block Producer Interface (BPI) Allows for Multiple inputs in A Multi-Input Transaction. To accommodation thesis cases, BIP 14 defines Substages, which are intermediate hashes that allow transactions to be executed efficiently.
When Creating A Substage, The Ethereum Virtual Machine (EVM) Substitutions The Previous Scriptpubkey For Each Input, resulting in Different Signature hashes. This Substitution is Necessary because the EVM Needs to Ensure That the Transaction’s Output Addresses and Values Match the Expected Ones.
Why Different Signatures?
The Different signatures are not arbitrary; They Serve A Specific Purpose:
- Consistency : By Using Different Inputs with the Same
Scriptpubkey, We Maintain Consistency in the Transaction’s Output Addresses and Values.
- Efficiency : The EVM can use thesis Subses to Optimize Transaction Processing, Reducing Computational Overhead and Improving Overall Efficiency.
- Security : Using Different Inputs Ensures That Transactions Cannot Be Executed Maliciously by Exploiting Weaknesses in the System.
In Conclusion
The signature hash of a multi-input transaction differs from its input hash due to the substitution of scriptpubkeys. This Design Choice is rooted in Maintaining Consistency, Optimizing Transaction Processing, and Ensuring Security. In Ethereum, we trust the EVM’s ability to substitute inputs correctly, allowing us to execute transactions efficiently and saafely.
Example use case
Consider A Multi-Input Transaction Where Two Users Want to Send Funds from One Account to Another Using Different Scriptpubkeys. To Execute This Transaction, The Substitution of Scriptpubkeys would Ensure That:
- The Output Addresses Match Expectations.
- Transaction processing is efficient.
- Security is mainted.
In Summary, The Different Signature hashes in Multi-input Transactions are a result of the EVM’s Ability to Substitute Scriptpubkeys, which Balances Consistency, Efficiency, and Security.