> ## Documentation Index
> Fetch the complete documentation index at: https://cofhe-docs.fhenix.zone/llms.txt
> Use this file to discover all available pages before exploring further.

# Require

> Understanding require statements with encrypted data in FHE

## Overview

The `require` statement in FHE contracts works similarly to [Conditions (if .. else)](/fhe-library/core-concepts/conditions) because both involve conditional logic on encrypted data. Just like you can't use traditional `if...else` statements with encrypted values, you also can't use standard `require` statements that depend on encrypted conditions.

<Warning>
  Traditional `require` statements that check encrypted conditions will leak information about your encrypted values through execution paths.
</Warning>

***

## Why Require is Like Conditions

Both `require` and conditional statements face the same fundamental challenge in FHE:

<CardGroup cols={2}>
  <Card title="Encrypted Evaluation" icon="lock">
    The condition being checked is encrypted, so the contract can't directly evaluate it to decide whether to revert.
  </Card>

  <Card title="Information Leakage" icon="shield-exclamation">
    If a transaction reverts based on an encrypted condition, observers can infer information about the encrypted data.
  </Card>
</CardGroup>

***

## The Solution

Instead of using `require` with encrypted conditions, you should:

1. **Use `FHE.select`** to handle the conditional logic (see [Conditions (if .. else)](/fhe-library/core-concepts/conditions))
2. **Only use `require` for non-encrypted conditions** like access control checks, address validation, or other plaintext values

```solidity theme={null}
// Good - require on plaintext condition
require(msg.sender == owner, "Not authorized");

// Good - use select for encrypted logic
euint32 result = FHE.select(encryptedCondition, valueA, valueB);

// Bad - require on encrypted condition is not possible!
// FHE.decrypt was removed — decryption is now off-chain only
// require(FHE.decrypt(encryptedValue.gt(threshold)), "Value too low");
```

***

## Learn More

For detailed guidance on handling conditional logic with encrypted data, see the [Conditions (if .. else)](/fhe-library/core-concepts/conditions) page.