SIP-44: Multi-Address Object Usage in Transactions

sips/sip-44.md

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+| SIP-Number          | 44 |
+| ---:                | :--- |
+| Title               | Multi-Address Object Usage in Transactions |
+| Description         | Enable transactions to use objects owned by multiple addresses with appropriate signatures |
+| Author              | Cyril Morlet \<[email protected]\> |
+| Editor              | Will Riches \<[email protected], @wriches\>  |
+| Type                | Standard |
+| Category            | Core |
+| Created             | 2024-11-22 |
+| Comments-URI        | https://sips.sui.io/comments-44 |
+| Status              | Draft |
+| Requires            | |
+
+## Abstract
+
+This SIP proposes extending Sui's transaction model to allow using objects owned by multiple addresses within a single transaction, provided all relevant address owners sign the transaction. This enhancement would enable secure multi-party atomic operations while maintaining Sui's ownership and security model.
+
+## Motivation
+
+Currently, Sui transactions can only use objects owned by the transaction sender, with a limited exception for a single gas sponsor. This restriction prevents several valuable use cases:
+
+1. Server-assisted operations where a server needs to provide admin/authority objects while users provide their own objects
+2. Direct peer-to-peer exchanges where two users want to atomically swap objects
+3. Multi-signature operations where multiple parties need to contribute specific objects to a transaction
+4. Multiple parties contributing to transaction gas costs, allowing fair distribution of fees in collaborative operations
+
+While single-party gas sponsorship exists, there's no mechanism to securely include objects from multiple owners or allow multiple parties to contribute to gas costs in a single atomic operation. This leads to complex multi-step transactions that are vulnerable to race conditions and require trust between parties.
+
+## Specification
+
+I propose extending the transaction system to:
+
+1. Allow transactions to reference objects owned by multiple addresses
+2. Require signatures from all addresses that own objects used in the transaction
+3. Maintain the existing sender model while adding additional object-owner signatures
+4. (optional) Enable multiple addresses to contribute gas objects to the same transaction
+
+The execution flow would be:
+
+1. Transaction creation includes list of all participating addresses
+2. Each required signer adds their signature
+3. Validation ensures all object owners have signed
+4. Normal transaction execution proceeds with expanded object access
+
+## Rationale
+
+This design would:
+
+1. Maintains Sui's strong ownership model by requiring signatures from all object owners
+2. Enables atomic multi-party operations while preserving the existing security model
+3. Provides flexibility for gas cost sharing without compromising the transaction model
+
+## Backwards Compatibility
+
+This change is backwards compatible:
+- Existing transactions remain valid with their current structure
+- New transaction format is a superset of the current format
+- No changes required for existing smart contracts
+
+## Security Considerations
+
+1. Signature Verification
+   - All signatures must be valid
+   - Order of signatures must not affect validation
+   - Clear failure modes for missing signatures
+
+2. Object Access Control
+   - Strict validation of object ownership
+   - Prevention of unauthorized object access
+   - Clear transaction failure if any object becomes unavailable
+
+3. Gas Safety
+   - Gas contribution amounts must be clearly specified
+   - Gas object ownership must be verified just like regular objects