Anti-Pattern: View Encrypted

🟢 Beginner | ⚠️ Anti-Patterns

Common mistake: expecting view functions to return plaintext instead of encrypted handles

Overview

This is one of the MOST COMMON mistakes when learning FHEVM. Developers expect view functions to return readable values, but they return encrypted handles that must be decrypted off-chain. Learn why this happens, see the common variations of this mistake, and understand the correct pattern: get handle from view function, then decrypt off-chain using fhevm.userDecryptEuint() with user signature.

Quick Start

# Create new project from this template
npx labz create anti-pattern-view-encrypted my-project

# Navigate and install
cd my-project
npm install

# Run tests
npx hardhat test

Code Explanation

The Mistake

The mistake: developers think calling getBalance() will return 1000, but it returns 0x1234... (an encrypted handle). You cannot read plaintext from view functions!

Lines 10-27

Why Not Work

View functions return handles (32-byte references to encrypted data). Decryption requires: permission check, user signature, and off-chain processing.

Lines 29-41

Correct Approach

Correct approach: grant permission with FHE.allow(), return handle from view function, then decrypt off-chain using fhevm.userDecryptEuint() with user signature.

Lines 43-58

Anti Pattern Example

ANTI-PATTERN function showing what NOT to expect. Developers call this expecting plaintext but get an encrypted handle instead.

Lines 78-92

Correct Example

CORRECT usage with full client-side code showing how to get handle and then decrypt off-chain properly.

Lines 96-121

FHE Operations Used

• FHE.fromExternal()

• FHE.allowThis()

• FHE.allow()

FHE Types Used

• euint64

• externalEuint64

Tags

anti-pattern mistake view decrypt handle common error beginner trap yaygin hata

Related Examples

• decryption-user-single

• anti-pattern-missing-allow

Prerequisites

Before this example, you should understand:

• encryption-single

Next Steps

After this example, check out:

• decryption-user-single

• anti-pattern-missing-allow

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