VeeDo Time-Lock to the Rescue

Yael Doweck

Product & Research at StarkWare

@YaelDoweck

Time-Lock as a Measure to Eliminate MEV

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Introduction to VeeDo

VeeDo Time-Lock

• is a delay function
• Long to compute
• is its inverse
• Fast to compute

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• VeeDo is also a VDF for randomness

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f(x, T) {

Repeat T times:

x ⇽ (x^1/3 + C) mod p

Return (x, T) }

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p is a 126-bit prime

1 multiplication ~ 4ns

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Sloth [LW 15, BBBF 19]

VeeDo Time-Lock Commitment

• Commit to a value v
• Apply inverse f on the value v:
• Reveal
• Compute the delay function f on the commitment c:
• Verify the reveal computation
• Option 1: compute the inverse function
• Option 2: a STARK proof attests to the validity of the computation
• Anyone can verify the proof very fast (logarithmic time)
• A smart contract can verify and register the result on-chain

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VeeDo to the Rescue!

Two approaches:

1. Time-locks as part of the protocol layer
2. Time-locks on Ethereum with smart contracts - supported today

Two approaches:

• Time-locks in the protocol layer
• Fully supported Time-locks on Ethereum today with smart contracts

Users send commitments to the mempool

Alice commits to value X

Carol commits to value Y

Bob commits to value Z

Mempool

Time-locked X

Time-locked Y

Time-locked Z

Each commitment has an expiration-time (smaller than time-lock delay)

Commitments are included in the blockchain

Miner

Submits a block containing time-locked transactions

Ethereum

Block:

Time-locked X

Time-locked Y

Time-locked Z

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MEV is minimized

Miner

Submits a block containing time-locked transactions

Ethereum

Block:

Time-locked X

Time-locked Y

Time-locked Z

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Time-locked transaction are ordered on-chain,

MEV is unknown

An operator/s unlocks the time-locks

Miner

Submits a block containing time-locked transactions

Computation Operator

Get time-locked transactions

and reveal them by performing a long serial computation

Ethereum

Block:

Time-locked X

Time-locked Y

Time-locked Z

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The operator submits the proof on-chain

Computation Operator

Verifier SC

X is valid=1

Y is valid=1

Z is valid=1

Submits a computation proof

The operator/s submits conditional transactions

Mempool

conditional X

conditional Y

conditional Z

Computation Operator

The miner checks each time-lock computation

Miner

Query condition on X

Query condition on Y

Query condition on Z

Verifier SC

X is valid=1

Y is valid=1

Z is valid=1

Creates a block with the verified values

Mempool

conditional X

conditional Y

conditional Z

Miner

Block:

conditional X

conditional Y

conditional Z

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Block is finalized, anyone can verify it

Miner

Ethereum

Block:

conditional X

conditional Y

conditional Z

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Verifier SC

X is valid=1

Y is valid=1

Z is valid=1

Block is finalized, anyone can verify it

Miner

Ethereum

Block:

conditional X

conditional Y

conditional Z

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Verifier SC

X is valid=1

Y is valid=1

Z is valid=1

Revealed transactions must be in the same order as the time-locked transactions

Two approaches:

• Time-locks in the protocol layer
• Fully supported Time-locks on Ethereum today with smart contracts

The operator/s computes the time-locks

Sequencer

List:

Time-locked X

Time-locked Y

Time-locked Z

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Sequencer SC

Send a list commitment (hash)

Commitments as calldata

Computation Operator

Get commitments list

and compute time-locks

The operator submits the proof

Logic SC

Computation Operator

Sequencer SC

Verifier SC

Submits the computation proof

Check that the sequence corresponds to the list commitment

Summary

• Privacy can reduce MEV
• VeeDo time-lock offers a solution for privacy in the sequencing phase
• There are multiple schemes to use VeeDo to minimize MEV
• Miners are the sequencers of time-locked transactions
• A smart contract stores the sequence