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Assertion Data Availability (Assertion DA) is the storage layer that maintains assertion bytecode and source code, making it accessible to Assertion Enforcers and providing transparency for users and auditors.

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Purpose

Assertion DA serves two primary functions:
  1. Persistent Storage: Maintains EVM bytecode of assertions in an accessible location
  2. Integrity Verification: Validates that on-chain assertion IDs match the Keccak256 hash of the actual assertion bytecode

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Key Concepts

Before diving into how Assertion DA works, it’s important to understand two key concepts: the Assertion ID and the DA Prover Signature.

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Assertion ID

The assertion ID is deterministically derived from the assertion bytecode: 
Assertion ID = Keccak256(Deployable_Assertion_EVM_Bytecode)
Where Deployable_Assertion_EVM_Bytecode is the flattened smart contract code and the constructor arguments. This ensures:
  • Each unique assertion has a unique identifier
  • Assertion integrity can be verified by recomputing the hash
  • Not compilable bytecode will fail execution deterministically, so no validation is needed at submission time

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Assertion DA Prover Signature

The Assertion DA prover signature is generated and returned by Assertion DA as part of storing the assertion. This proof is used during deployment of the assertion to guarantee that the assertion bytecode is available on Assertion DA.

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Current Implementation

The current implementation is operated by Phylax Systems with a highly available infrastructure:
  • Storage: Off-chain server stores assertion bytecode and source code
  • Access: Publicly accessible for transparency and verification
  • Integration: Works with pcl and the Phylax platform. See the Architecture Overview for details.
  • Roadmap: Decentralization planned for 2026

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How It Works

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Storing Assertions

When you store an assertion using pcl: 
pcl store MyAssertion
pcl does the following:
  1. Compiles assertion contracts to EVM bytecode
  2. Uploads flattened source code and compiler options to Assertion DA
  3. Returns the assertion ID (Keccak256 hash of the bytecode) and DA prover signature
Only authorized admins can deploy, modify, or remove assertions for their contracts. This is enforced on-chain by the Credible Layer smart contracts, which verify administrative authority (such as owner-based checks) before allowing assertion management operations. The on-chain State Oracle contracts also enforce the configured timelock for both adding and removing assertions. Ownership verification will be expanded and improved in future versions to support additional ownership patterns. See Ownership Verification for details.

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Retrieving Assertions

Assertion Enforcers fetch assertions from Assertion DA upon on-chain deployment:
  1. On-Chain Deployment Event: When an assertion is deployed on-chain, the addAssertion event is emitted
  2. Fetch Bytecode: Assertion Enforcers detect the event and fetch the assertion bytecode from Assertion DA using the assertion ID
  3. Cache Internally: Store assertion bytecode in internal cache for future use
During transaction validation, Assertion Enforcers use the cached bytecode directly—no fetching occurs on the hot path. This ensures high-performance validation without network latency. See the Architecture Overview for details on how assertions are executed during validation.

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Complete Lifecycle

The complete flow from assertion development to enforcement involves multiple steps:
  1. Development: Write and test assertions locally using pcl
  2. Storage: Store assertion bytecode in Assertion DA using pcl store, which returns the assertion ID
  3. Submission: Submit the assertion ID to your project in the Phylax platform using pcl submit
  4. Deployment: Review the assertion, link it to specific contract addresses, choose Staging or Production environment, and sign the transaction to deploy it on-chain
  5. Marked for Enforcement/Staging: After the add transaction is accepted on-chain, the State Oracle timelock begins. During that period, the assertion is marked for enforcement (production) or marked for staging (staging environment)
  6. Enforced/Staged: After the timelock expires, Assertion Enforcers fetch assertions from Assertion DA and execute them during block production. Assertions become enforced or staged
If you later remove the assertion, that removal is also delayed by the configured State Oracle timelock before the assertion stops applying to transactions. For a detailed view of how these components interact, see the System Architecture section in the Architecture Overview.

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Design Rationale

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Why Off-Chain Storage?

  • Cost Efficiency: EVM bytecode can be large; on-chain storage would be prohibitively expensive
  • Performance: Faster retrieval and caching for high-frequency validation
  • Flexibility: Enables future improvements without base layer changes
  • Additional Metadata: Supports metadata that wouldn’t be feasible on-chain, such as instant source code verification for transparency and auditing

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Why No On-Chain Bytecode Validation?

The protocol intentionally omits bytecode validation because:
  • PhEVM execution is deterministic
  • Not compilable bytecode will consistently fail execution
  • This allows Assertion Enforcers to safely discard invalid assertions without verification overhead

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Security Considerations

Availability: The highly available infrastructure ensures consistent uptime. Assertion Enforcers cache assertion bytecode locally, so existing enforced assertions continue operating even during potential downtime. Only new assertion deployments require Assertion DA connectivity. Integrity: The Keccak256 hash verification ensures assertions haven’t been modified. Each assertion ID uniquely corresponds to its bytecode. Transparency: Assertions can be retrieved via Assertion DA, enabling users and auditors to verify security measures. Incentive Alignment: Invalid assertions only harm the developer who submitted them, as they will fail execution deterministically.

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Next Steps

Quickstart Guide

Learn how to store and submit assertions

CLI Reference

Complete reference for pcl commands

Architecture Overview

Understand how Assertion DA fits into the system

Glossary

Learn more about Assertion DA terminology