A validity proof is a succinct cryptographic certificate that mathematically proves the correctness of a batch of transactions or a state transition, without requiring a verifier to re-execute the entire computation. Generated by a prover, the proof is verified by a verifier using a much more efficient algorithm, ensuring that the new state is a valid result of applying the transactions according to the system's rules. This mechanism is the core innovation behind Zero-Knowledge Rollups (ZK-Rollups) and validiums, which use it to compress transaction data and provide strong security guarantees.
LABS
Glossary
Validity Proof
A validity proof is a cryptographic proof, such as a ZK-SNARK or ZK-STARK, that attests to the correctness of a computation, used by ZK-Rollups to verify state transitions.
Chainscore © 2026
definition
CRYPTOGRAPHIC VERIFICATION
What is a Validity Proof?
A validity proof is a cryptographic proof that attests to the correctness of a computation or state transition, enabling trust-minimized scaling for blockchains.
The creation of a validity proof typically involves constructing a zk-SNARK (Succinct Non-Interactive Argument of Knowledge) or a zk-STARK (Scalable Transparent Argument of Knowledge). These protocols allow the prover to demonstrate knowledge of a witness (the transaction data and execution trace) that satisfies a specific computational statement, while revealing nothing else. The resulting proof is succinct (small in size) and can be verified in constant time, making it highly scalable. This process provides cryptographic security, meaning fraud is computationally infeasible, unlike in fraud-proof systems which rely on a challenge period.
The primary application of validity proofs is in Layer 2 scaling. In a ZK-Rollup, transactions are executed off-chain, and a validity proof is posted on the base Layer 1 chain (like Ethereum) alongside a minimal amount of data. The L1 smart contract verifies the proof and updates its state accordingly. This architecture offers significant benefits: trust minimization (security inherits from the L1), fast finality (once the proof is verified, the state is final), and data efficiency. Validity proofs are also fundamental to creating privacy-preserving applications, as they can prove statements about private data without revealing the data itself.
how-it-works
ZK-PROOF MECHANICS
How a Validity Proof Works
A technical breakdown of the cryptographic mechanism that allows one party to prove to another that a statement is true without revealing the underlying data.
A validity proof is a cryptographic proof, typically a zero-knowledge proof (ZKP), that cryptographically attests to the correctness of a state transition or computation. The core process involves a prover generating a proof that a new state root is the correct result of executing a batch of transactions, and a verifier checking this proof with minimal computational effort. This mechanism is the foundation for ZK-Rollups and other validity-proof-based scaling solutions, enabling them to inherit the security of a parent chain like Ethereum without requiring all nodes to re-execute every transaction.
The workflow begins with a prover (often a sequencer node) executing transactions off-chain and batching them. It then generates a SNARK (Succinct Non-interactive Argument of Knowledge) or STARK (Scalable Transparent Argument of Knowledge) proof. This proof mathematically demonstrates that the new state root in the rollup's Merkle tree is the valid outcome, given the old state and the batched transactions. The proof is succinct, meaning it is small and fast to verify, regardless of the complexity of the computation it proves.
The generated proof and the new state root are then published to the parent chain (Layer 1). A smart contract on L1, known as a verifier contract, receives this data. The contract contains the verification key or logic specific to the proof system. It runs a deterministic verification algorithm on the proof. If the proof is valid, the contract accepts the new state root, finalizing the state transition. This process provides cryptographic security guarantees equivalent to executing the transactions on L1, as forging a valid proof is computationally infeasible.
Key properties of this system include data compression, as only the proof and minimal data are posted on-chain, and trust minimization, as the security relies on cryptography rather than honest majority assumptions. Unlike fraud proofs, which are optimistic and have a challenge period, validity proofs provide instant finality for the L1-verified state. This makes them particularly suitable for applications requiring high security and fast withdrawal guarantees, such as decentralized exchanges and payment networks.
In practice, generating a validity proof is computationally intensive, requiring specialized prover hardware. However, verification is intentionally lightweight, allowing even resource-constrained nodes (like Ethereum validators) to confirm the integrity of massive computations. This asymmetry is the key innovation that enables scalable blockchain architectures, where execution is moved off-chain and security is maintained through cryptographic verification on-chain.
key-features
MECHANICAL PROPERTIES
Key Features of Validity Proofs
Validity proofs are cryptographic certificates that verify the correctness of state transitions off-chain. Their core features define their security model, efficiency, and trust assumptions.
01
Succinctness & Scalability
A validity proof is a succinct cryptographic argument (e.g., a SNARK or STARK) that proves the correctness of a batch of transactions. This allows a single, small proof to verify massive computational work, enabling layer-2 scaling where the main chain (L1) only needs to verify the proof, not re-execute the transactions.
- Data Compression: Proofs are kilobytes in size, representing gigabytes of computation.
- Throughput: Enables thousands of transactions per second (TPS) off-chain with minimal on-chain verification cost.
02
Cryptographic Security
The security of the system rests on cryptographic assumptions (e.g., the hardness of discrete logarithms or collision-resistant hashes) rather than economic incentives or honest majority assumptions. A validity proof provides cryptographic guarantees that a state transition is mathematically correct.
- Soundness: It is computationally infeasible to generate a valid proof for an invalid state transition.
- Trust Minimization: Users do not need to trust operators; they trust the math and the underlying blockchain for data availability.
03
Data Availability Requirement
For a validity proof to be meaningful, the input data (transaction data) it proves must be available. Data availability ensures anyone can reconstruct the state and challenge fraud if needed. Systems using validity proofs typically post this data to the L1 blockchain.
- On-Chain Data: Transaction data is published as calldata or in data availability committees (DACs).
- Verification Without Trust: With the data and the proof, anyone can verify the new state is correct.
04
Fast Finality for All Users
Once a validity proof is verified on the L1, the state transition is immediately finalized for all users. There is no challenge period, unlike in fraud proof systems. This provides instant strong finality, meaning withdrawals can be processed immediately after proof verification.
- No Waiting Periods: Eliminates the 7-day withdrawal delays common in optimistic rollups.
- Universal Certainty: All observers, including bridges and exchanges, can trust the finality instantly.
05
Computational Intensity & Prover Cost
Generating a validity proof is a computationally expensive process (proof generation) that requires specialized hardware or services. This creates a distinction between the prover (who creates the proof) and the verifier (the L1 contract that checks it).
- Prover Overhead: Proof generation time and cost are the primary bottlenecks for throughput and latency.
- Asymmetric Efficiency: Verification is cheap and fast, but proof creation is resource-intensive.
06
Trusted Setup (for some systems)
Some validity proof systems, particularly those using SNARKs (like Groth16, PLONK), require a trusted setup ceremony to generate public parameters. This is a one-time ritual where participants must destroy a secret "toxic waste" to ensure the system's security.
- Perpetual Security: If the ceremony is compromised, all future proofs could be forged.
- Trustless Alternatives: STARKs do not require a trusted setup, relying only on cryptographic hashes.
SCALING MECHANISM COMPARISON
Validity Proof vs. Fraud Proof
A technical comparison of the two primary cryptographic proof systems used for blockchain scaling and security.
| Feature | Validity Proof (ZK Proof) | Fraud Proof (Interactive / Optimistic) |
|---|---|---|
Core Mechanism | Prover generates a cryptographic proof (e.g., zk-SNARK, zk-STARK) that a state transition is valid. | Watchers monitor state and submit a challenge with proof if they detect invalid state transitions. |
Trust Assumption | Cryptographic (trustless). Relies on mathematical soundness. | Economic (1-of-N honest actor). Requires at least one honest verifier. |
Withdrawal / Finality Delay | Immediate (proven on-chain). | Challenge period (typically 7 days). |
On-Chain Data Requirement | Only proof data (small, constant size). | All transaction data must be posted (for potential challenges). |
Computational Overhead | High (proof generation is computationally intensive). | Low (only requires re-execution in dispute cases). |
Security Guarantee | Validity is cryptographically guaranteed. No window for fraud. | Security is probabilistic; relies on economic incentives and watchtowers. |
Primary Use Case | ZK-Rollups (e.g., zkSync, StarkNet). | Optimistic Rollups (e.g., Arbitrum, Optimism). |
Privacy Potential | Yes (proofs can hide transaction details). | No (all transaction data is public). |
examples
IMPLEMENTATIONS
Types of Validity Proofs
Validity proofs are cryptographic systems that mathematically guarantee the correctness of state transitions. Different proof systems offer distinct trade-offs in proof size, verification speed, and computational overhead.
03
Plonk & Variants
Permutations over Lagrange-bases for Oecumenical Noninteractive arguments of Knowledge is a universal, updatable SNARK system.
- Key Innovation: Introduces a universal and updatable trusted setup. A single ceremony can be used for any program up to a certain size, and the setup can be securely updated by new participants.
- Benefits: Reduces the overhead and risk of application-specific trusted setups. Enables efficient proof aggregation and recursion.
- Example Use: Foundational for many zkEVMs like Scroll, Polygon zkEVM, and zkSync's Boojum.
04
Bulletproofs
A non-interactive zero-knowledge proof protocol that is short and does not require a trusted setup.
- Key Properties: Proofs are longer and verification is slower than SNARKs, but the lack of a trusted setup is a significant security advantage. They are particularly efficient for range proofs (proving a value lies within a range).
- Primary Use Case: Originally designed for confidential transactions in Monero. Also used in some earlier scaling solutions and as a component in more complex proof systems.
05
Proof Aggregation & Recursion
Advanced techniques that combine multiple proofs into one, enabling scalability.
- Proof Aggregation: Bundles many individual transaction proofs into a single, final validity proof for a block. This amortizes the cost of on-chain verification.
- Proof Recursion: A prover generates a proof that validates the correctness of another proof's verification. This creates a proof of proofs, allowing for the creation of a single proof for an entire rollup chain's history.
- Impact: Critical for making zk-Rollups economically viable by minimizing the on-chain footprint of verification.
06
zkEVMs
Zero-Knowledge Ethereum Virtual Machines are a specific application of validity proofs that generate proofs for the execution of EVM-compatible transactions.
- Goal: Provide full Ethereum equivalence (bytecode-level) or high-level language equivalence for developers, allowing them to deploy existing smart contracts with minimal changes.
- Types: Range from Type 1 (fully Ethereum-equivalent) to Type 4 (high-level language equivalence), with varying trade-offs in prover efficiency.
- Examples: zkSync Era, Scroll, Polygon zkEVM, and Starknet (with its Cairo VM) are leading implementations.
technical-details
VALIDITY PROOF
Technical Details: Proving Systems
A deep dive into the cryptographic mechanism that underpins trustless scaling and privacy in blockchain systems.
A validity proof is a cryptographic attestation, generated by a proving system, that a computation (such as a batch of blockchain transactions) was executed correctly without requiring a verifier to re-execute it. This proof, often called a zero-knowledge proof (ZKP) or succinct non-interactive argument of knowledge (SNARK), allows a single entity to prove to any verifier that a statement is true, revealing only the truth of the statement and not the underlying data. The core innovation is succinctness: the proof is small and fast to verify, regardless of the complexity of the original computation.
The process involves two parties: a prover and a verifier. The prover runs the computation and uses a specialized proving algorithm to generate a compact proof. The verifier, who may have limited computational resources, can then check this proof using a corresponding verification algorithm. This separation is fundamental to ZK-Rollups, a leading Layer 2 scaling solution, where a prover generates a validity proof for thousands of transactions off-chain. The proof is then posted on the base Layer 1 chain (like Ethereum), where a smart contract verifies it, allowing the entire batch to be settled with the same security guarantees as the underlying blockchain.
Different proving systems offer trade-offs between proof size, verification speed, prover time, and trust assumptions. SNARKs require a trusted setup ceremony but produce very small proofs with extremely fast verification. STARKs do not need a trusted setup and offer quantum resistance, but generate larger proofs. Bulletproofs are another type used primarily for confidential transactions. The choice of system depends on the application's requirements for scalability, setup complexity, and post-quantum security.
Beyond scaling, validity proofs enable powerful privacy applications through zero-knowledge proofs. Protocols like Zcash use them to prove a transaction is valid (e.g., the sender has sufficient funds and knows the spending key) without revealing the sender, recipient, or transaction amount. This allows for selective disclosure, where users can prove specific attributes (like being over 18) from private credentials without exposing the credentials themselves, a concept central to decentralized identity systems.
The security of a system using validity proofs rests on the cryptographic soundness of the underlying proving system and the correct implementation of its circuits or constraints. A sound proof system makes it computationally infeasible for a malicious prover to generate a valid proof for a false statement. Therefore, the verifier's acceptance of a validity proof provides a strong cryptographic guarantee of computational integrity, making it a cornerstone for building verifiable and trust-minimized systems in blockchain and beyond.
ecosystem-usage
IMPLEMENTATIONS
Ecosystem Usage: Protocols Using Validity Proofs
Validity proofs are not a theoretical concept but a foundational technology actively deployed across major blockchain ecosystems. This section highlights key protocols that have integrated validity proofs to achieve scalability, privacy, or interoperability.
06
Application-Specific zkChains
Many protocols use validity proofs for specific applications rather than general-purpose scaling. Examples include:
- dYdX: A decentralized exchange that used a ZK-Rollup (v3) for high-throughput perpetual trading.
- Immutable X: A Validium for NFT trading, using STARK proofs for validity but storing data off-chain.
- Loopring: An early ZK-Rollup protocol for decentralized exchange and payment functions. These chains demonstrate the flexibility of validity proofs for optimizing particular use cases.
security-considerations
VALIDITY PROOF
Security Considerations & Trust Assumptions
Validity proofs are cryptographic systems that mathematically verify the correctness of off-chain computations, forming the core security model for Zero-Knowledge Rollups (ZK-Rollups). This section breaks down their components and inherent trust assumptions.
01
Core Cryptographic Mechanism
A validity proof is a succinct cryptographic argument, typically a Zero-Knowledge Succinct Non-Interactive Argument of Knowledge (zk-SNARK) or zk-STARK, that proves a state transition (e.g., a batch of transactions) was executed correctly according to the rules of the underlying blockchain. The proof is generated off-chain by a prover and verified on-chain by a smart contract, requiring only the proof and minimal public data.
02
Trust Assumption: Cryptographic Security
Validity proofs rely solely on the mathematical soundness of their underlying cryptographic primitives. The primary trust assumption is that the cryptographic algorithms (e.g., elliptic curve pairings for SNARKs, hash functions for STARKs) are secure and that the initial trusted setup ceremony (for most SNARKs) was performed correctly and is now "toxic waste"-free. If these hold, the system provides cryptographic finality.
03
Prover Honesty & Data Availability
While the proof guarantees computational integrity, two other assumptions are critical:
- Prover Liveness: At least one honest and capable prover must be available to generate proofs for new state transitions.
- Data Availability: The transaction data (calldata) for the proven batch must be published and accessible on the base layer (L1). Without it, users cannot reconstruct their state or challenge fraud, breaking the system's self-custody guarantee.
04
Comparison: Validity vs. Fraud Proofs
This is the fundamental security dichotomy in scaling:
- Validity Proofs (ZK-Rollups): Provide cryptographic assurance of correctness. Invalid state transitions are mathematically impossible to prove. Offers fast finality.
- Fraud Proofs (Optimistic Rollups): Assume transactions are valid but allow a challenge period (e.g., 7 days) for anyone to submit a proof of fraud. Security relies on the liveness of at least one honest verifier.
05
Implementation Risks & Attack Vectors
Real-world risks stem from implementation flaws, not the core cryptography:
- Verifier Contract Bugs: A bug in the on-chain verification smart contract could accept invalid proofs.
- Prover Centralization: If proof generation is centralized, it creates a liveness failure point and potential censorship risk.
- Upgrade Keys: Admin keys with the ability to upgrade the protocol's proving system or verifier contract introduce a trusted third-party risk.
06
Example: zkEVM Proof Systems
Projects implement validity proofs differently:
- zkSync Era & Polygon zkEVM: Use custom zk-SNARK circuits (e.g., PLONK, Redshift) to prove EVM-compatible execution.
- Scroll: Utilizes a zkEVM architecture with a zk-SNARK-based rollup and an open-source zkEVM circuit.
- Starknet: Uses zk-STARKs, which do not require a trusted setup but generate larger proofs, trading off cost for post-quantum resistance assumptions.
FAQ
Common Misconceptions About Validity Proofs
Validity proofs, such as ZK-SNARKs and ZK-STARKs, are cryptographic primitives that power zero-knowledge rollups, but their technical nature leads to widespread misunderstandings about their capabilities, security, and performance.
No, validity proofs and fraud proofs are fundamentally different security mechanisms for verifying off-chain computation. A validity proof (or ZK proof) is a cryptographic certificate that mathematically guarantees the correctness of a state transition before it is accepted. In contrast, a fraud proof is an optimistic mechanism that allows anyone to challenge and disprove an incorrect state transition after it has been posted, relying on a dispute window. Validity proofs provide cryptographic finality, while fraud proofs offer economic finality after a challenge period.
VALIDITY PROOFS
Frequently Asked Questions (FAQ)
A technical deep dive into the cryptographic mechanism that enables trust-minimized scaling and verification on blockchains.
A validity proof is a cryptographic proof that verifies the correctness of a batch of transactions or state transitions without re-executing them. It works by having a prover (often a sequencer) generate a succinct proof, like a zk-SNARK or zk-STARK, that mathematically attests that a new state root is the correct result of executing a set of transactions from a known prior state. A verifier (e.g., an L1 smart contract) can then check this proof in constant time, regardless of the computation size, ensuring the new state is valid and fraud is impossible.
Key Steps:
- Execution: The prover executes transactions off-chain.
- Proof Generation: The prover creates a cryptographic proof of correct execution.
- Verification: The verifier checks the proof's validity on-chain.
- State Update: Upon successful verification, the new state root is accepted.
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