Data Availability Sampling (DAS) is a probabilistic guarantee, not a finality mechanism. It ensures data is published, but does not verify its correctness. A sequencer can still post invalid state transitions that are available for sampling.
the-modular-blockchain-thesis-explained
Blog
Why Data Availability Sampling Is Incomplete Without Fraud Proofs
Data Availability Sampling (DAS) ensures data is published, but only fraud or validity proofs can enforce correct execution. This is the critical, often misunderstood, link in the modular blockchain security model.
introduction
THE DATA
The Modular Security Fallacy
Data Availability Sampling alone creates a false sense of security without a live fraud proof mechanism to enforce it.
Fraud proofs are the enforcement layer that converts data availability into security. Without a live, permissionless network of verifiers to submit fraud proofs, like Arbitrum's AnyTrust or Optimism's fault proofs, the system reverts to honest-minority assumptions.
The fallacy is assuming availability equals settlement. This is the core vulnerability separating validiums from optimistic rollups. EigenDA-powered validiums, like those built with the Polygon CDK, trade off this security for lower cost.
Evidence: A system using Celestia for DA but lacking fraud proofs has a 21-day withdrawal delay, identical to an optimistic rollup's challenge period. The security model is identical; only the data source changed.
key-trends
THE COMPLETE PICTURE
The Two-Layer Security Model
Data Availability Sampling (DAS) alone creates a probabilistic safety net; fraud proofs are the deterministic hammer that finalizes disputes.
01
The Problem: DAS is Probabilistic, Not Guaranteed
DAS allows light nodes to sample small chunks of data with high confidence, but it's a statistical game. A malicious sequencer could, in theory, hide a single critical transaction and get lucky against samplers. The security guarantee approaches but never reaches 100%.
- Risk: A 1-of-N fraud can slip through with non-zero probability.
- Reality: Full security requires a mechanism to prove and slash fraud after the fact.
99.99%
Probabilistic Safety
>30
Sampling Rounds
02
The Solution: Fraud Proofs as the Enforcement Layer
Fraud proofs are the deterministic backstop. If a verifier detects invalid state transitions (e.g., double-spends, invalid signatures), they can generate a succinct proof. This proof is verified on-chain, slashing the sequencer's bond and forcing a reversion.
- Guarantee: Cryptographic, 100% verifiable correctness.
- Efficiency: Only one honest, fully-synced node is needed to keep the system honest.
100%
Deterministic
1
Honest Node Needed
03
The Architecture: Celestia's Modular Blueprint
Celestia pioneered the separation of consensus & data availability (DA) from execution. Rollups post data to Celestia and rely on its DAS for data availability and a separate fraud/validity proof system (like Arbitrum Nitro or zk-rollups) for execution correctness.
- Separation of Concerns: DA layer ensures data is published; proof system ensures it's correct.
- Ecosystem Example: dYmension RollApps use Celestia for DA and a fraud-proof-based settlement layer.
2-Layer
Separation
$1B+
Rollup TVL
04
The Incomplete Alternative: DAS-Only "Security"
Relying solely on DAS without fraud proofs is like having a smoke detector but no fire department. Projects like EigenDA and Avail provide high-throughput DA, but rollups using them must implement their own fraud/validity proof system for full security. The DA layer cannot detect logic errors.
- Limitation: Only guarantees data exists, not that it's valid.
- Vulnerability: Execution faults become social consensus or governance issues.
DA-Only
Incomplete Guard
0
Execution Checks
deep-dive
THE VERIFICATION GAP
DAS Finds the Data, Proofs Judge the Computation
Data availability sampling ensures data is published, but fraud proofs are required to verify its correct execution.
Data Availability Sampling (DAS) is a liveness guarantee, not a correctness guarantee. It allows light clients to probabilistically confirm that block data is published and retrievable, solving the data availability problem for scaling solutions like Celestia and Avail. This prevents data withholding attacks but does nothing to verify state transitions.
Fraud proofs are the execution layer's immune system. They are succinct cryptographic arguments that allow a single honest node to prove an invalid state transition to the rest of the network. Without them, a rollup like Arbitrum or Optimism is just a centralized sequencer making promises; the security model collapses to a multisig.
The combination creates a trust-minimized scaling stack. DAS provides the raw data, and fraud proofs provide the arbitration. This is the foundational architecture for sovereign rollups and validiums, where execution is decoupled from settlement. Systems like EigenDA focus solely on the data layer, delegating verification to a separate proof system.
Evidence: Optimism's Cannon fraud proof system took years to deploy, leaving the network in a softer security model. The delay highlights that implementing a robust, decentralized fraud proof mechanism is the final, complex step in achieving full L2 security.
DATA AVAILABILITY & SETTLEMENT
The Modular Security Matrix: Who Handles What?
Comparing the security guarantees of different data availability (DA) and settlement layer configurations, highlighting why DAS alone is insufficient without fraud proofs.
| Security Component | Pure DAS (e.g., Celestia) | DAS + Fraud Proofs (e.g., Arbitrum Nova) | Integrated Settlement (e.g., Ethereum L1) |
|---|---|---|---|
Data Availability Sampling (DAS) | |||
Data Availability Guarantee | ~99.99% (Probabilistic) | ~99.99% (Probabilistic) | 100% (Deterministic) |
Fraud Proof Window | 7 Days | N/A (Settles via Validity Proofs) | |
Settlement Finality Time | N/A (No Settlement) | ~1 Week (Optimistic Challenge Period) | ~12 Minutes (Ethereum Block Finality) |
State Validity Enforcement | |||
Bridging Security Model | Based on DA Security | Based on DA + Fraud Proof Security | Native L1 Security |
Key Risk | Invalid state can be published & made available | Invalid state can be published but is slashed if proven | State validity is enforced by consensus |
counter-argument
THE VERIFICATION GAP
The ZK-Rollup Counterpoint (And Why It Proves the Rule)
ZK-Rollups appear to bypass the need for fraud proofs, but their security model reveals a deeper dependency on data availability.
ZK-Rollups are not exempt. They replace interactive fraud proofs with succinct validity proofs, but these proofs only verify state transitions. The underlying data availability problem remains. A sequencer can withhold transaction data, making state updates unverifiable despite a valid ZK-SNARK.
Validity proofs need data. A ZK proof confirms computation integrity, not data existence. Clients must still download or sample the data to reconstruct the state. This makes Data Availability Sampling (DAS) a prerequisite, not an alternative, for both Optimistic and ZK architectures.
The counterpoint proves the rule. The existence of secure ZK-rollups like zkSync Era and StarkNet demonstrates that fraud proofs and validity proofs solve different problems. Both ultimately rely on a secure data layer, whether via Ethereum calldata, EigenDA, or Celestia.
Evidence: StarkEx processes over 100M transactions. Its security is a hybrid: a STARK proof for validity and Ethereum L1 for data availability. Without the latter, the proof is an empty promise.
risk-analysis
DATA AVAILABILITY
The Risks of an Incomplete Stack
Data Availability Sampling (DAS) is a breakthrough for scaling, but without fraud proofs, it's a half-built bridge to disaster.
01
The Sampling Fallacy
DAS alone only proves data exists, not that it's correct. A malicious sequencer can publish invalid state transitions alongside available data, creating a cryptoeconomic time bomb.\n- Liveness Attack: Honest nodes sample and accept available but fraudulent data.\n- State Corruption: The invalid state becomes canonical, requiring a social fork to revert.
0
Validity Guarantees
02
Celestia's Core Limitation
As a pure DA layer, Celestia explicitly outsources execution and settlement, creating a critical security gap. Rollups built on it must implement their own fraud/validity proof systems (like Arbitrum Nitro or zkSync), or they inherit no security for state validity.\n- Modular Risk: The security of the rollup is now the weakest link in a 3-layer chain (Execution, Settlement, DA).\n- Settlement Dependence: Forces reliance on a separate settlement layer (e.g., Ethereum, Celestia) for dispute resolution.
3-Layer
Trust Assumption
03
The Full Stack: Avail & EigenDA
Next-gen DA layers like Avail and EigenDA are converging on the necessity of integrated proofs. Avail is building Avail Nexus for cross-rollup settlement and light-client proofs, while EigenDA leverages EigenLayer's cryptoeconomic security for slashing.\n- Unified Security: Aims to provide data and validity guarantees within a coherent system.\n- Ecosystem Lock-in: Creates a more vertically integrated, but potentially less modular, security model.
Integrated
Proof Stack
04
The Ethereum Roadmap: Danksharding
Proto-Danksharding (EIP-4844) introduces blob storage, but full Danksharding with DAS is designed to work within Ethereum's existing fraud-proof and consensus framework. The Ethereum Execution Layer and consensus clients provide the inherent settlement and slashing for validity.\n- Holistic Design: DAS is a component within a complete L1 security system.\n- No New Trust: Leverages the ~$500B+ economic security of Ethereum for both availability and correctness.
$500B+
Backing Security
takeaways
THE MISSING HALF
TL;DR for Architects
Data Availability Sampling (DAS) ensures data is published, but only Fraud Proofs can prove it was used correctly. One without the other is a security risk.
01
The Sampling Blind Spot
DAS nodes only check for data presence, not data validity. A malicious sequencer can publish gibberish or invalid state transitions that still passes sampling, leading to an incorrect chain.\n- Risk: Liveness without correctness.\n- Analogy: Checking a book's pages exist vs. verifying the story makes sense.
0%
Validity Checked
02
Fraud Proofs as the Arbiter
A single honest full node can cryptographically prove an invalid state transition to all light clients. This is the enforcement mechanism that makes DAS-secured chains trust-minimized.\n- Core Function: Convert a full node's knowledge into a verifiable proof.\n- Requirement: Needs the full data to construct, which DAS guarantees is available.
1
Honest Node Needed
03
Celestia's Modular Gamble
Celestia provides pure DA and defers execution & settlement. This pushes the fraud proof requirement onto the rollup (e.g., using Arbitrum Nitro or Optimism's fault proofs). The security model is fragmented.\n- Architectural Choice: Decouples availability from verification.\n- Systemic Risk: A rollup with weak fraud proofs breaks, even with perfect DA.
N/A
Rollup-Dependent
04
The Ethereum L1 Benchmark
Ethereum's monolithic L1 combines data availability (blobs) with integrated fraud/validity proofs (consensus). Full nodes perform both roles, creating a unified security base. This is the gold standard rollups like Arbitrum and Optimism inherit.\n- Integrated Security: DA and execution validity are enforced in the same layer.\n- Contrast: Pure modular stacks lack this inherent coordination.
Monolithic
Base Layer
05
zk-Proofs as a Nuclear Option
Validity proofs (ZKPs) mathematically guarantee correctness, making reactive fraud proofs obsolete. This is why zkRollups (zkSync, StarkNet) are considered more secure than optimistic rollups. They complete the DA picture proactively.\n- Superior Model: DA sampling + ZKP = unconditional safety.\n- Trade-off: Higher computational cost and proving complexity.
100%
Proven Correct
06
The Interoperability Attack Vector
Bridges and cross-chain apps (e.g., LayerZero, Axelar) that trust a DAS-secured chain are exposed if its fraud proof system fails. The entire modular ecosystem's security is only as strong as its weakest verification layer.\n- Systemic Risk: A failure in one rollup's proofs can cascade.\n- Due Diligence: Must audit the entire stack, not just the DA layer.
Chainlink
Oracle Risk
ENQUIRY
Get In Touch
today.
Our experts will offer a free quote and a 30min call to discuss your project.
NDA Protected
Confidentiality24h Response
Time to ValueDirectly to Engineering Team
No Sales Fluff10+
Protocols Shipped
$20M+
TVL Overall