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Encrypt Single Value

🟢 Beginner | 🔐 Encryption

How to encrypt and send a single value to a FHEVM contract

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Overview

This fundamental example teaches the complete encryption flow in FHEVM. Learn how clients encrypt values using createEncryptedInput(), send them to contracts as external* types, and how contracts receive and store them using FHE.fromExternal(). This is the foundation for all FHE applications - every encrypted value starts with this flow.

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Quick Start

# Create new project from this template
npx labz create encryption-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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Imports

Import both internal types (euint*, ebool) for storage and external types (externalEuint*, externalEbool) for receiving encrypted inputs from clients.

Lines 1-5

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Store Uint8

Receive encrypted 8-bit value from client. Client uses add8() to encrypt, contract receives as externalEuint8, converts with FHE.fromExternal(), then sets ACL permissions.

Lines 38-53

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Store Uint64

Receive encrypted 64-bit value - the most common type for balances, amounts, and IDs. Client uses add64() with BigInt values (n suffix for large numbers).

Lines 78-95

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Store Bool

Receive encrypted boolean. Client uses addBool() to encrypt true/false. Useful for private flags, votes, and conditions.

Lines 99-115

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Plaintext Warning

WARNING: FHE.asEuint64() takes a plaintext value that IS VISIBLE on-chain! Only use for initialization with known public values. For private values, always use encrypted input from client.

Lines 120-140

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FHE Operations Used

  • FHE.fromExternal()

  • FHE.asEuint64()

  • FHE.allowThis()

  • FHE.allow()

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FHE Types Used

  • euint8

  • euint16

  • euint32

  • euint64

  • ebool

  • externalEuint8

  • externalEuint16

  • externalEuint32

  • externalEuint64

  • externalEbool

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Tags

encryption fromExternal externalEuint64 createEncryptedInput input beginner sifreleme

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Related Examples

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Next Steps

After this example, check out:

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