# Comparing Ethereum Rollup Interoperability Solutions

## Overview

This article compares major approaches to achieving interoperability between Ethereum rollups, analyzing their technical architectures, security models, and trade-offs. We'll examine both general-purpose solutions and specialized protocols targeting specific use cases like token transfers.

## Core Solutions Analysis

### 1. PreAuth ERC20 (Credit Card Pattern)

#### Architecture
- L2-first hold recording with L1 settlement
- Single rollup designation per L1 account
- Batched settlement pattern
- Cross-layer balance verification

#### Key Innovations
- Zero L1 gas cost for holds
- Unified L1 liquidity model
- Credit card pre-authorization pattern
- Real-time balance verification

#### Trade-offs
- Limited to single rollup per account
- Token-specific solution
- Requires rollup-specific integrations
- Settlement latency for finality

### 2. Polygon AggLayer

#### Architecture
- Cross-rollup virtual machine (CVM)
- Shared state execution layer
- Unified proving system
- Cross-rollup message passing protocol

#### Key Innovations
- Universal cross-rollup composability
- Shared security model
- Optimistic execution with fraud proofs
- Standardized message format (ERC-7683)

#### Trade-offs
- Complex implementation
- Higher overhead for simple transfers
- New trust assumptions
- Requires rollup modifications

### 3. Espresso Sequencer

#### Architecture
- Decentralized sequencing layer
- Ordered transaction bundles
- Cross-rollup state verification
- MEV protection mechanisms

#### Key Innovations
- Fair transaction ordering
- Cross-rollup atomic operations
- MEV redistribution
- Sequencer decentralization

#### Trade-offs
- Additional consensus layer
- Increased latency
- New economic model needed
- Complex coordination

### 4. ERC-7683: Cross Chain Intents Standard

#### Architecture
- Intent-based cross-chain communication
- Chain-agnostic intent specification
- Standardized intent validation
- Unified execution model
- Cross-chain settlement protocol

#### Key Innovations
- Intent-centric design
- Universal message format
- Composable intents
- Chain-agnostic specification
- Standardized validation rules

#### Trade-offs
- Protocol overhead for simple operations
- Complex intent resolution
- New validation requirements
- Coordination complexity

### 5. Omni Network

#### Architecture
- Dedicated interoperability layer
- Optimistic verification
- Cross-chain virtual machine
- Universal asset representation

#### Key Innovations
- Chain-agnostic protocol
- Optimistic fraud proofs
- Unified asset standard
- Cross-chain native execution

#### Trade-offs
- New bridge security assumptions
- Additional protocol overhead
- Complex economic model
- Requires widespread adoption

## Technical Comparison Matrix

### Core Technical Metrics
| Feature | PreAuth ERC20 | AggLayer | Espresso | ERC-7683 | Omni |
|---------------------------|---------------|----------|-----------|-----------|---------|
| L1 Gas Cost (Basic Op) | ~5k* | ~50k | ~100k | ~40k | ~80k |
| Implementation Complexity | Low | High | High | Medium | High |
| Time to Market | Short | Long | Medium | Medium | Medium |
| Rollup Modifications | Minor | Major | Major | Moderate | Minor |
| State Verification | Real-time | Delayed | Delayed | Intent | Delayed |

### Security & Trust Model
| Feature | PreAuth ERC20 | AggLayer | Espresso | ERC-7683 | Omni |
|---------------------------|---------------|----------|-----------|-----------|---------|
| Security Inheritance | Full L1 | Partial | Partial | Full L1 | New |
| Trust Assumptions | Minimal | Medium | Medium | Low | High |
| Censorship Resistance | High | Medium | High | High | Medium |
| MEV Protection | Limited | Moderate | Strong | Moderate | Limited |
| Settlement Finality | Immediate | Delayed | Fast | Intent | Delayed |

### Ethereum Value Alignment & Trust Model
| Feature | PreAuth ERC20 | AggLayer | Espresso | ERC-7683 | Omni |
|-----------------------------|---------------|----------|-----------|-----------|---------|
| Trust Source | Pure ETH | Hybrid | Hybrid | Hybrid | New |
| Additional Trust Elements | None | CVM | Sequencer| Fillers | Bridge |
| Security Inheritance | 100% L1 | Partial | Partial | Partial | External|
| Forced Exit Available* | Yes | Limited | Limited | Limited | No |
| Upgrades Impact Trust** | No | Yes | Yes | Yes | Yes |
| Validator Set Required | No | Yes | Yes | Yes | Yes |
| External Dependencies*** | None | CVM | Sequencer| Fillers/Oracle | Bridge |

\* Ability to exit to L1 without cooperation from the protocol's operators/validators
\** Whether protocol upgrades can affect security assumptions
\*** Required components beyond Ethereum L1 consensus

Trust Model Details:

1. PreAuth ERC20
- Pure Ethereum Security: All security derives from L1
- No Additional Validators: Uses only Ethereum validators
- Trust Assumptions:
* L1 ERC20 contract correctness
* L2 hold recording (but can exit to L1)
* No additional trust elements

2. AggLayer
- Hybrid Security Model: Combines L1 + CVM
- Additional Trust Required:
* Cross-VM validators
* Fraud proof system
* State verification layer
- New Trust Elements:
* CVM operator honesty
* Cross-chain message verification
* Proof system correctness

3. Espresso
- Hybrid Security Model: L1 + Sequencer
- Additional Trust Required:
* Sequencer network
* MEV protection system
* Order fairness guarantees
- New Trust Elements:
* Sequencer honesty
* Transaction ordering system
* Block production rules

4. ERC-7683
- Hybrid Security Model: L1 + Fillers Network
- Additional Trust Required:
* Filler network for order execution
* Oracle systems for external data
* Settlement contract security
- New Trust Elements:
* Filler honesty for execution
* Order dissemination infrastructure
* Cross-chain validation system
* Settlement contract correctness

5. Omni
- New Security Model: Bridge-based
- Additional Trust Required:
* Bridge validators
* External consensus
* Asset representation system
- New Trust Elements:
* Bridge operator honesty
* External chain security
* Cross-chain asset mapping

\* Ability to exit to L1 without cooperation from the protocol's operators/validators
\** Whether protocol upgrades can affect security assumptions
\*** Required components beyond Ethereum L1 consensus

Trust Model Details:

1. PreAuth ERC20
- Pure Ethereum Security: All security derives from L1
- No Additional Validators: Uses only Ethereum validators
- Trust Assumptions:
* L1 ERC20 contract correctness
* L2 hold recording (but can exit to L1)
* No additional trust elements

2. AggLayer
- Hybrid Security Model: Combines L1 + CVM
- Additional Trust Required:
* Cross-VM validators
* Fraud proof system
* State verification layer
- New Trust Elements:
* CVM operator honesty
* Cross-chain message verification
* Proof system correctness

3. Espresso
- Hybrid Security Model: L1 + Sequencer
- Additional Trust Required:
* Sequencer network
* MEV protection system
* Order fairness guarantees
- New Trust Elements:
* Sequencer honesty
* Transaction ordering system
* Block production rules

4. ERC-7683
- Pure Ethereum Security: Based on L1
- No Additional Validators: Uses only Ethereum
- Trust Assumptions:
* L1 contract correctness
* Intent verification logic
* No additional trust elements

5. Omni
- New Security Model: Bridge-based
- Additional Trust Required:
* Bridge validators
* External consensus
* Asset representation system
- New Trust Elements:
* Bridge operator honesty
* External chain security
* Cross-chain asset mapping

### Payment Suitability (Customer to Merchant)
| Feature | PreAuth ERC20 | AggLayer | Espresso | ERC-7683 | Omni |
|---------------------------|---------------|----------|-----------|-----------|---------|
| Transaction Speed | Instant** | Medium | Fast | Fast | Medium |
| Cost Per Transaction | Very Low | High | High | Medium | High |
| UX Simplicity | High | Low | Medium | Medium | Medium |
| Payment Finality | Guaranteed | Probable | Fast | Intent | Delayed |
| Merchant Integration | Simple | Complex | Medium | Medium | Complex |
| Failed Payment Handling | Automatic | Manual | Manual | Intent | Manual |
| Chargeback Support*** | Built-in | No | No | Possible | No |

\* Innovation Location: Indicates where protocol innovation primarily occurs
** Initial authorization is instant, settlement is batched
*** Similar to traditional payment card pre-authorization pattern

*Amortized cost after batching

## Security Analysis

### PreAuth ERC20
- Inherits L1 security
- Single rollup designation reduces attack surface
- Real-time balance verification
- Clear settlement finality

### AggLayer
- New shared security model
- Cross-rollup fraud proofs
- Complex coordination requirements
- Potential cross-chain attack vectors

### Espresso
- Sequencer security assumptions
- MEV protection mechanisms
- Transaction ordering guarantees
- Cross-rollup atomicity risks

### ERC-7683
- Standard compliant validation
- Intent-based security model
- Cross-chain coordination risks
- Intent resolution guarantees

### Omni
- Bridge security risks
- New consensus assumptions
- Cross-chain verification complexity
- Asset representation risks

## Use Case Optimization

### Token Transfers
1. PreAuth ERC20: Optimized
2. ERC-7683: Very Good
3. Omni: Good
4. AggLayer: Possible but complex
5. Espresso: General support

### Smart Contract Interaction
1. AggLayer: Optimized
2. ERC-7683: Very Good
3. Omni: Good
4. Espresso: Good
5. PreAuth: Limited

### DeFi Operations
1. AggLayer: Optimized
2. ERC-7683: Optimized
3. Espresso: Good
4. Omni: Good
5. PreAuth: Limited

## Future Considerations

### Technical Evolution
- EIP-4844 impact
- Proto-danksharding considerations
- ZK-proof improvements
- Cross-rollup standards

### Economic Models
- Gas market effects
- MEV considerations
- Liquidity implications
- Validator incentives

### Adoption Factors
- Developer experience
- Integration complexity
- Security auditing
- User experience

## Conclusion

Each solution optimizes for different aspects of the interoperability challenge:

1. PreAuth ERC20: Efficient token operations with minimal L1 footprint
2. AggLayer: Universal composability with higher complexity
3. Espresso: Fair ordering and MEV protection
4. ERC-7683: Standardized cross-chain communication with intent focus
5. Omni: General interoperability with new trust model

The optimal choice depends on specific use case requirements, with specialized solutions like PreAuth potentially offering better efficiency for specific operations while general solutions provide broader functionality at higher complexity.

## References

1. EIP-4844: Proto-Danksharding
2. ERC-7683: Cross-Chain Interaction Standard
3. L2Beat: Rollup Security Analysis
4. Ethereum Foundation Research Forum
5. Vitalik's Layer 2 Scaling Post
6. Justin Drake's Beam Chain Roadmap

*Note: Gas costs and performance metrics are estimates based on current implementations and may vary with network conditions and specific deployments.*

Author: Joan | Researcher at [Sprintcheckout](https://sprintcheckout.com/)