Handle Journey

🟢 Beginner | 🔑 Understanding Handles

Complete lifecycle of an FHE handle from birth to death

Overview

This educational template demonstrates the complete lifecycle of FHE handles in FHEVM. A handle is a 256-bit reference to encrypted data stored in the coprocessor. This template walks through all 5 stages: Birth (handle creation from plaintext or user input), Permission (ACL grants via allow/allowTransient), Operation (creating child handles via FHE operations), Storage (persisting handles in contract state), and Death (decryption reveals the value). Essential for understanding how encrypted values work in FHEVM.

Quick Start

# Create new project from this template
npx labz create handle-journey my-project

# Navigate and install
cd my-project
npm install

# Run tests
npx hardhat test

Code Explanation

Stage1 Birth

Handle creation from plaintext (FHE.asEuint64) and user input (FHE.fromExternal). Shows how handles are born.

Lines 85-114

Stage2 Permission

Granting permanent (FHE.allow) and transient (FHE.allowTransient) permissions on handles.

Lines 120-150

Stage3 Operation

FHE operations create NEW child handles. Original handles remain unchanged. Demonstrates add, multiply, and compare.

Lines 156-210

Stage4 Storage

Handles stored in contract state persist between transactions. Shows how to maintain encrypted state.

Lines 216-230

Stage5 Death

Decryption is the 'death' of a handle - the value becomes public. Shows 3-step async decryption pattern.

Lines 236-275

FHE Operations Used

  • FHE.FHE.asEuint64()

  • FHE.FHE.fromExternal()

  • FHE.FHE.add()

  • FHE.FHE.mul()

  • FHE.FHE.gt()

  • FHE.FHE.allow()

  • FHE.FHE.allowThis()

  • FHE.FHE.allowTransient()

  • FHE.FHE.makePubliclyDecryptable()

  • FHE.FHE.checkSignatures()

FHE Types Used

  • euint64

  • ebool

  • externalEuint64

Tags

handles lifecycle birth permission operation decryption educational

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Next Steps

After this example, check out:

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