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Public Decrypt Single Value

🟡 Intermediate | 🔓 Decryption

3-step async public decryption: the CURRENT pattern for revealing encrypted values to everyone

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Overview

This CRITICAL example teaches the 3-step async public decryption pattern in FHEVM. The old Gateway/Oracle callback pattern has been REMOVED. Learn how to: (1) request reveal with FHE.makePubliclyDecryptable(), (2) decrypt off-chain with relayer-sdk publicDecrypt(), and (3) finalize with FHE.checkSignatures(). Use this when you need to reveal values publicly like lottery results, auction winners, or voting tallies.

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Quick Start

# Create new project from this template
npx labz create decryption-public-single my-project

# Navigate and install
cd my-project
npm install

# Run tests
npx hardhat test

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Code Explanation

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Step1 Request

STEP 1: Call FHE.makePubliclyDecryptable() to mark the encrypted value for public decryption. This enables off-chain services to decrypt it.

Lines 73-92

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Step2 Handle

STEP 2 (off-chain): Return the encrypted handle for off-chain decryption. Client uses fhevmInstance.publicDecrypt([handle]) to get clearValue and proof.

Lines 94-109

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Step3 Finalize

STEP 3: Finalize with proof from KMS. FHE.checkSignatures() verifies the proof is valid. If valid, the decrypted value is stored on-chain publicly.

Lines 111-155

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Proof Verification

Build ciphertext and cleartext arrays for verification. FHE.checkSignatures() takes three params: ciphertext handles, encoded cleartexts, and the proof from KMS.

Lines 138-148

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FHE Operations Used

  • FHE.fromExternal()

  • FHE.makePubliclyDecryptable()

  • FHE.checkSignatures()

  • FHE.allowThis()

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FHE Types Used

  • euint64

  • externalEuint64

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Tags

decryption public makePubliclyDecryptable checkSignatures async 3-step reveal KMS proof

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Related Examples

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Prerequisites

Before this example, you should understand:

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Next Steps

After this example, check out:

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